The very name Byzantine illustrates the misconceptions to which the empire's history has often been subject, for its inhabitants would hardly have considered the term appropriate to themselves or to their state. Theirs was, in their view, none other than the Roman Empire, founded shortly before the beginning of the Christian Era by God's grace to unify his people in preparation for the coming of his Son. Proud of that Christian and Roman heritage, convinced that their earthly empire so nearly resembled the heavenly pattern that it could never change, they called themselves Romaioi, or Romans. Modern historians agree with them only in part. The term East Rome accurately described the political unit embracing the Eastern provinces of the old Roman Empire until 476, while there were yet two emperors. The same term may even be used until the last half of the 6th century, as long as men continued to act and think according to patterns not unlike those prevailing in an earlier Roman Empire. During these same centuries, nonetheless, there were changes so profound in their cumulative effect that after the 7th century state and society in the East differed markedly from their earlier forms. In an effort to recognize that distinction, historians traditionally have described the medieval empire as “Byzantine.”

The latter term is derived from the name Byzantium, borne by a colony of ancient Greek foundation on the European side of the Bosporus, midway between the Mediterranean and the Black Sea; the city was, by virtue of its location, a natural transit point between Europe and Asia Minor (Anatolia). Refounded as the “new Rome” by the emperor Constantine (Constantine I) in 330, it was endowed by him with the name Constantinople (Istanbul), the city of Constantine. The derivation from Byzantium is suggestive in that it emphasizes a central aspect of Byzantine civilization: the degree to which the empire's administrative and intellectual life found a focus at Constantinople from 330 to 1453, the year of the city's last and unsuccessful defense under the 11th (or 12th) Constantine. The circumstances of the last defense are suggestive, too, for in 1453 the ancient, medieval, and modern worlds seemed briefly to meet. The last Constantine fell in defense of the new Rome built by the first Constantine. Walls that had held firm in the early Middle Ages against German, Hun, Avar, Slav, and Arab were breached finally by modern artillery, in the mysteries of which European technicians had instructed the most successful of the Central Asian invaders: the Ottoman Turks.

The fortunes of the empire thus were intimately entwined with those of peoples whose achievements and failures constitute the medieval history of both Europe and Asia. Nor did hostility always characterize the relations between Byzantines and those whom they considered “barbarian.” Even though the Byzantine intellectual firmly believed that civilization ended with the boundaries of his world, he opened it to the barbarian, provided that the latter (with his kin) would accept Baptism and render loyalty to the emperor. Thanks to the settlements that resulted from such policies, many a name, seemingly Greek, disguises another of different origin: Slavic, perhaps, or Turkish. Barbarian illiteracy, in consequence, obscures the early generations of more than one family destined to rise to prominence in the empire's military or civil service. Byzantium was a melting-pot society, characterized during its earlier centuries by a degree of social mobility that belies the stereotype, often applied to it, of an immobile, caste-ridden society.

A source of strength in the early Middle Ages, Byzantium's central geographical position served it ill after the 10th century. The conquests of that age presented new problems of organization and assimilation, and these the emperors had to confront at precisely the time when older questions of economic and social policy pressed for answers in a new and acute form. Satisfactory solutions were never found. Bitter ethnic and religious hostility marked the history of the empire's later centuries, weakening Byzantium in the face of new enemies descending upon it from east and west. The empire finally collapsed when its administrative structures could no longer support the burden of leadership thrust upon it by military conquests.

The Roman Empire, the ancestor of the Byzantine, remarkably blended unity and diversity, the former being by far the better known since its constituents were the predominant features of Roman civilization. The common Latin language, the coinage, the “international” army of the Roman legions, the urban network, the law, and the Greco-Roman heritage of civic culture loomed largest among those bonds that Augustus and his successors hoped would bring unity and peace to a Mediterranean world exhausted by centuries of civil war. To strengthen these sinews of imperial civilization, the emperors hoped that a lively and spontaneous trade might develop among the several provinces. At the pinnacle of this world stood the emperor himself, the man of wisdom who would shelter the state from whatever mishaps fortune had darkly hidden. The emperor alone could provide this protection since, as the embodiment of all the virtues, he possessed in perfection those qualities displayed only imperfectly by his individual subjects.

The Roman formula of combating fortune with reason and therewith assuring unity throughout the Mediterranean world worked surprisingly well in view of the pressures for disunity that time was to multiply. Conquest had brought regions of diverse background under Roman rule. The Eastern provinces were ancient and populous centres of that urban life that for millennia had defined the character of Mediterranean civilization. The Western provinces had only lately entered upon their own course of urban development under the not always tender ministrations of their Roman masters.

Each of the aspects of unity enumerated above had its other side. Not everyone understood or spoke Latin. Paralleling and sometimes influencing Roman law were local customs and practices, understandably tenacious by reason of their antiquity. Pagan temples, Jewish synagogues, and Christian baptisteries attest to the range of organized religions with which the official forms of the Roman state, including those of emperor worship, could not always peacefully coexist. And far from unifying the Roman world, economic growth often created self-sufficient units in the several regions, provinces, or great estates.

Given the obstacles against which the masters of the Roman state struggled, it is altogether remarkable that Roman patriotism was ever more than an empty formula, that cultivated gentlemen from the Pillars of Hercules to the Black Sea were aware that they had “something” in common. This “something” might be defined as the Greco-Roman civic tradition in the widest sense of its institutional, intellectual, and emotional implications. Grateful for the conditions of peace that fostered it, men of wealth and culture dedicated their time and resources to glorifying that tradition through adornment of the cities that exemplified it and through education of the young who they hoped might perpetuate it.

Upon this world the barbarians descended after about AD 150. To protect the frontier against them, warrior emperors devoted whatever energies they could spare from the constant struggle to reassert control over provinces where local regimes emerged. In view of the ensuing warfare, the widespread incidence of disease, and the rapid turnover among the occupants of the imperial throne, it would be easy to assume that little was left of either the traditional fabric of Greco-Roman society or the bureaucratic structure designed to support it.

Neither assumption is accurate. Devastation was haphazard, and some regions suffered while others did not. In fact, the economy and society of the empire as a whole during that period was more diverse than it had ever been. Impelled by necessity or lured by profit, people moved from province to province. Social disorder opened avenues to eminence and wealth that the more stable order of an earlier age had closed to the talented and the ambitious. For personal and dynastic reasons, emperors favoured certain towns and provinces at the expense of others, and the erratic course of succession to the throne, coupled with a resulting constant change among the top administrative officials, largely deprived economic and social policies of recognizable consistency.

The means they adopted to achieve these ends differ so profoundly that one, Diocletian, looks to the past and ends the history of Rome; the other, Constantine, looks to the future and founds the history of Byzantium. Thus, in the matter of succession to the imperial office, Diocletian adopted precedents he could have found in the practices of the 2nd century AD. He associated with himself a coemperor, or Augustus. Each Augustus then adopted a young colleague, or Caesar, to share in the rule and eventually to succeed the senior partner. This rule of four, or tetrarchy, failed of its purpose, and Constantine replaced it with the dynastic principle of hereditary succession, a procedure generally followed in subsequent centuries. To divide administrative responsibilities, Constantine replaced the single praetorian prefect, who had traditionally exercised both military and civil functions in close proximity to the emperor, with regional prefects established in the provinces and enjoying civil authority alone. In the course of the 4th century, four great “regional prefectures” emerged from these Constantinian beginnings, and the practice of separating civil from military authority persisted until the 7th century.

Contrasts in other areas of imperial policy are equally striking. Diocletian persecuted Christians (Christianity) and sought to revive the ancestral religion. Constantine, a convert to the new faith, raised it to the status of a “permitted religion.” Diocletian established his headquarters at Nicomedia, a city that never rose above the status of a provincial centre during the Middle Ages, while Constantinople, the city of Constantine's foundation, flourished mightily. Diocletian sought to bring order into the economy by controlling wages and prices and by initiating a currency reform based upon a new gold piece, the aureus, struck at the rate of 60 to the pound of gold. The controls failed and the aureus vanished, to be succeeded by Constantine's gold solidus. The latter piece, struck at the lighter weight of 72 to the gold pound, remained the standard for centuries. For whatever reason, in summary, Constantine's policies proved extraordinarily fruitful. Some of them—notably hereditary succession, the recognition of Christianity, the currency reform, and the foundation of the capital—determined in a lasting way the several aspects of Byzantine civilization with which they are associated.

Yet it would be a mistake to consider Constantine a revolutionary or to overlook those areas in which, rather than innovating, he followed precedent. Earlier emperors had sought to constrain groups of men to perform certain tasks that were deemed vital to the survival of the state but that proved unremunerative or repellent to those forced to assume the burden. Such tasks included the tillage of the soil, which was the work of the peasant, or colonus; the transport of cheap bulky goods to the metropolitan centres of Rome or Constantinople, which was the work of the shipmaster, or navicularius; and services rendered by the curiales (curia), members of the municipal senate charged with the assessment and collection of local taxes. Constantine's laws in many instances extended or even rendered hereditary these enforced responsibilities, thus laying the foundations for the system of collegia, or hereditary state guilds, that was to be so noteworthy a feature of late-Roman social life. Of particular importance, he required the colonus (peasant) to remain in the locality to which the tax lists ascribed him.

Whether innovative or traditional, Constantine's measures determined the thrust and direction of imperial policy throughout the 4th century and into the 5th. The state of the empire in 395 may, in fact, be described in terms of the outcome of Constantine's work. The dynastic principle was established so firmly that the emperor who died in that year, Theodosius I, could bequeath the imperial office jointly to his sons, both of whom were young and incompetent: Arcadius in the East and Honorius in the West. Never again would one man rule over the full extent of the empire in both its halves. Constantinople had probably grown to a population of between 200,000 and 500,000; in the 5th century the emperors sought to restrain rather than promote its growth. After 391 Christianity was far more than one among many religions: from that year onward, imperial decree prohibited all forms of pagan cult, and the temples were closed. Imperial pressure was often manifest at the church councils of the 4th century, with the emperor assuming a role he was destined to fill again during the 5th century in defining and suppressing heresy.

The empire's economy had prospered in a spotty fashion. Certain provinces, or parts of provinces such as northern Italy, flourished commercially as well as agriculturally. Constantinople, in particular, influenced urban growth and the exploitation of agricultural frontiers. Balkan towns along the roads leading to the great city prospered, while others not so favoured languished and even disappeared. Untilled land in the hilly regions of northern Syria fell under the plow to supply foodstuffs for the masses of Constantinople. As the 4th century progressed, not only did Constantine's solidus remain indeed solid gold, but evidence drawn from a wide range of sources suggests that gold in any form was far more abundant than it had been for at least two centuries. It may be that new sources of supply for the precious metal had been discovered: these perhaps were in spoils plundered from pagan temples; or perhaps were from mines newly exploited in western Africa and newly available to the lands of the empire, thanks to the appearance of camel-driving nomads who transported the gold across the Sahara to the Mediterranean coastline of North Africa.

The extreme social mobility noted in the late 3rd and early 4th centuries seems less characteristic of the second half of the latter century. Certainly the emperors continued their efforts to bind men collectively to their socially necessary tasks, but the repetition of laws tying the colonus to his estate, the navicularius to his ship, and the curialis to his municipal senate suggests that these edicts had little effect. Indeed, it would be a mistake to conclude from such legislation that Roman society was universally and uniformly organized in castes determined in response to imperial orders. There was always a distinction between what an emperor wanted and what he could obtain, and, as the foregoing survey has suggested, there were distinctions among the provinces as well.

Even before the end of the first quarter of the 5th century, these provincial differences were visible; and, in no small degree, they help to explain the survival of imperial government and Greco-Roman civilization in the East while both eventually perished in the West. Throughout the Eastern provinces, population levels seem to have remained higher, and the emperors in Constantinople never had to search (at least until the 6th century) for men to fill the ranks of their armies. As might be expected in those eastern lands in which urban civilization was several centuries old, cities persisted and, with them, a merchant class and a monetary economy. Eastern merchants, known in the sources as Syrians, assumed the carrying trade between East and West, often establishing colonies in the beleaguered cities of the latter region.

Most important, the emperor in the East never lost access to, or control over, his sources of manpower and money. An older and probably more wealthy senatorial class, or aristocracy, in the West consolidated its great estates and assumed a form of protection or patronage over the labouring rural classes, depriving the state of desperately needed military and financial services. The senatorial class in the East seems to have been of more recent origin, its beginnings to be found among those favourites or parvenus who had followed Constantine to his new capital. By the early 5th century, their wealth seems to have been, individually, much less than the resources at the disposal of their Western counterparts; their estates were far more scattered and their rural dependents less numerous. They were thus less able to challenge the imperial will and less able to interpose themselves between the state, on the one hand, and its potential soldiers or taxpayers, on the other.

Neither in West nor East did Theodosius' policy of accommodation and alliance prove popular. The Goths, like most Germanic peoples with the exception of the Franks and the Lombards, had been converted to Arian (Arianism) Christianity, which the Catholic, or Orthodox, Romans considered a dangerous heresy. The warlike ways of the Germans found little favour with a senatorial aristocracy essentially pacifist in its outlook, and the early 5th century is marked in both halves of the empire by reactions against Germanic leaders in high office. At Constantinople in 400, for example, the citizens rose against the senior officer of the imperial guard (magister militum), Gainas, slaughtering him together with his Gothic followers. Although this particular revolt was, in many respects, less productive of immediate results than similar episodes in the West, and the Germanic leaders later reappeared in roles of command throughout the East, the latter acted thenceforth as individuals without the support of those nearly autonomous groups of soldiers that western barbarian commanders continued to enjoy.

Furthermore, the East made good use of its resources in gold, in native manpower, and in diplomacy, while quickly learning how best to play off one enemy against another. In the reign of Theodosius II (408–450), the Huns (Hun) under their chieftain Attila received subsidies of gold that both kept them in a state of uneasy peace with the Eastern Empire and may have proved profitable to those merchants of Constantinople who traded with the barbarians. When Marcian (ruled 450–457) refused to continue the subsidies, Attila was diverted from revenge by the prospect of conquests in the West. He never returned to challenge the Eastern Empire, and, with his death in 453, his Hunnic empire fell apart. Both Marcian and his successor, Leo I (ruled 457–474), had ruled under the tutelage of Flavius Ardaburius, Aspar; but Leo resolved to challenge Aspar's pre-eminence and the influence of the Goths elsewhere in the empire by favouring the warlike Isaurians and their chieftain, Tarasicodissa, whom he married to the imperial princess, Ariadne. The Isaurian followers of Tarasicodissa, who was to survive a stormy reign as the Emperor Zeno (474–491), were rough mountain folk from southern Anatolia and culturally probably even more barbarous than the Goths or the other Germans. Yet, in that they were the subjects of the Roman emperor in the East, they were undoubtedly Romans and proved an effective instrument to counter the Gothic challenge at Constantinople. In the prefecture of Illyricum, Zeno ended the menace of Theodoric the Amal by persuading him (488) to venture with his Ostrogoths into Italy. The latter province lay in the hands of the German chieftain Odoacer, who in 476 had deposed Romulus Augustulus, the last Roman emperor in the West. Thus, by suggesting that Theodoric conquer Italy as his Ostrogothic kingdom, Zeno maintained at least a nominal supremacy in that western land while ridding the Eastern Empire of an unruly subordinate.

With Zeno's death and the accession of the Roman civil servant Anastasius I (ruled 491–518), Isaurian occupation of the imperial office ended, but it was not until 498 that the forces of the new emperor effectively took the measure of Isaurian resistance. After the victory of that year, the loyal subject of the Eastern Roman emperor could breathe easily: Isaurians had been used to beat Germans, but the wild mountain folk had, in their turn, failed to take permanent possession of the imperial office. Imperial authority had maintained its integrity in the East while the Western Empire had dissolved into a number of successor states: the Angles and Saxons had invaded Britain as early as 410; the Visigoths had possessed portions of Spain since 417, and the Vandals had entered Africa in 429; the Franks, under Clovis I, had begun their conquest of central and southern Gaul in 481; and Theodoric was destined to rule in Italy until 526.

If ethnic hostility within the empire was less a menace around the year 500 than it had often been in the past, dissensions stemming from religious controversy seriously threatened imperial unity, and the political history of the next century cannot be understood without some examination of the so-called monophysite heresy. It was the second great heresy in the Eastern Empire, the first having been the dispute occasioned by the teachings of the Alexandrian presbyter Arius (Arianism), who, in an effort to maintain the uniqueness and majesty of God the Father, had taught that he alone had existed from eternity, while God the Son had been created in time. Thanks in part to imperial support, the Arian heresy had persisted throughout the 4th century and was definitively condemned only in 381 with promulgation of the doctrine that Father and Son were of one substance and thus coexistent.

If the Fathers of the 4th century quarreled over the relations between God the Father and God the Son, those of the 5th century faced the problem of defining the relationship of the two natures—the human and the divine—within God the Son, Christ Jesus. The theologians of Alexandria generally held that the divine and human natures were united indistinguishably, whereas those of Antioch taught that two natures coexisted separately in Christ, the latter being “the chosen vessel of the Godhead . . . the man born of Mary.” In the course of the 5th century, these two contrasting theological positions became the subject of a struggle for supremacy among the rival sees of Constantinople, Alexandria, and Rome. Nestorius (Nestorian), patriarch of Constantinople in 428, adopted the Antiochene formula, which, in his hands, came to stress the human nature of Christ to the neglect of the divine. His opponents (first the Alexandrian patriarch, Cyril (Cyril of Alexandria, Saint), and later Cyril's followers, Dioscorus and Eutyches) in reaction emphasized the single divine nature of Christ, the result of the Incarnation. Their belief in Monophysitism, or the one nature of Christ as God the Son, became extraordinarily popular throughout the provinces of Egypt and Syria. Rome, in the person of Pope Leo I (Leo I, Saint), declared in contrast for Dyophysitism, a creed teaching that two natures, perfect and perfectly distinct, existed in the single person of Christ. At the Council of Chalcedon (Chalcedon, Council of) (451), the latter view triumphed thanks to the support of Constantinople, which changed its position and condemned both Nestorianism, or the emphasis on the human nature of Christ, and Monophysitism, or the belief in the single divine nature.

More important for the purposes of military and political history than the theological details of the conflict was the impact Monophysitism produced on the several regions of the Mediterranean world. Partly because it provided a formula to express resistance to Constantinople's imperial rule, Monophysitism persisted in Egypt and Syria. Until these two provinces were lost to Islām in the 7th century, each Eastern emperor had somehow to cope with their separatist tendencies as expressed in the heresy. He had either to take arms against Monophysitism and attempt to extirpate it by force, to formulate a creed that would somehow blend it with Dyophysitism, or frankly to adopt the heresy as his own belief. None of these three alternatives proved successful, and religious hostility was not the least of the disaffections that led Egypt and Syria to yield, rather readily, to the Arab conqueror. If ever the East Roman emperor was to reassert his authority in the West, he necessarily had to discover a formula that would satisfy Western orthodoxy while not alienating Eastern Monophysitism.

In the reign of Anastasius I (491–518), all these tendencies of the 5th century found their focus: the sense of Romanitas, which demanded a Roman rather than an Isaurian or a German emperor, the conflict between Orthodoxy and Monophysitism, and the persisting economic prosperity of the Eastern Roman Empire. Acclaimed and elected as the Roman and Orthodox emperor who would end both the hated hegemony of the Isaurians and the detested activity of the Monophysite heretics, Anastasius succeeded in the first of these objectives while failing in the second. While he defeated the Isaurians and transported many of them from their Anatolian (Anatolia) homeland into Thrace, he gradually came to support the Monophysite heresy despite the professions of Orthodoxy he had made upon the occasion of his coronation. If his policies won him followers in Egypt and Syria, they alienated his Orthodox subjects and led, finally, to constant unrest and civil war.

Anastasius' economic policies were far more successful; if they did not provide the basis for the noteworthy achievements of the 6th century in military affairs and the gentler arts of civilization, they at least explain why the Eastern Empire prospered in those respects during the period in question. An inflation of the copper currency, prevailing since the age of Constantine, finally ended with welcome results for those members of the lower classes who conducted their operations in the base metal. Responsibility for the collection of municipal taxes was taken from the members of the local senate and assigned to agents of the praetorian prefect. Trade and industry were probably stimulated by the termination of the chrysargyron, a tax in gold paid by the urban classes. If, by way of compensating for the resulting loss to the state, the rural classes had then to pay the land tax in money rather than kind, the mere fact that gold could be presumed to be available in the countryside is a striking index of rural prosperity. In the East, the economic resurgence of the 4th century had persisted, and it is not surprising that Anastasius enriched the treasury to the extent of 320,000 pounds of gold during the course of his reign.

With such financial resources at their disposal, the Emperor's successors could reasonably hope to reassert Roman authority among the western Germanic successor states, provided they could accomplish two objectives: first, they must heal the religious discord among their subjects; second, they must protect the eastern frontier against the threat of Sāsānian Persia. Since there was, in fact, to be concurrent warfare on both fronts during the 6th century, some knowledge of the age-old rivalry between Rome and Persia (Iran, ancient) is essential to an understanding of the problems confronted by the greatest among Anastasius' successors, Justinian I (ruled 527–565), as he undertook the conquest of the West.

In 224 the ancient Persian Empire had passed into the hands of a new dynasty, the Sāsānians (Sāsānian dynasty), whose regime brought new life to the enfeebled state. Having assured firm control over the vast lands already subject to them, the Sāsānians took up anew the old struggle with Rome for northern Mesopotamia and its fortress cities of Edessa and Nisibis, lying between the Tigris and the Euphrates. In the course of the 4th century, new sources of hostility emerged as East Rome became a Christian empire. Partly by reaction, Sāsānian Persia strengthened the ecclesiastical organization that served its Zoroastrian (Zoroastrianism) religion; intolerance and persecution became the order of the day within Persia, and strife between the empires assumed something of the character of religious warfare. Hostilities were exacerbated when Armenia, lying to the north between the two realms, converted to Christianity and thus seemed to menace the religious integrity of Persia. If small-scale warfare during the 4th and 5th centuries rarely erupted into major expeditions, the threat to Rome nonetheless remained constant, demanding vigilance and the construction of satisfactory fortifications. By 518, the balance might be said to have tipped in the favour of Persia as it won away the cities of Theodosiopolis, Amida, and Nisibis.

After 550, it is possible to begin to speak of a medieval Byzantine, rather than an ancient East Roman, empire. Of the four traumas that eventually transformed the one into the other—namely, pestilence, warfare, social upheaval, and the Arab Muslim assault of the 630s—the first two were features of Justinian's reign.

Justinian is but one example of the civilizing magic that Constantinople often worked upon the heirs of those who ventured within its walls. Justin, the uncle, was a rude and illiterate soldier; Justinian, the nephew, was a cultivated gentleman, adept at theology, a mighty builder of churches, and a sponsor of the codification of Roman law. All these accomplishments are, in the deepest sense of the word, civilian, and it is easy to forget that Justinian's empire was almost constantly at war during his reign. The history of East Rome during that period illustrates, in classical fashion, how the impact of war can transform ideas and institutions alike.

The reign opened with external warfare and internal strife. From Lazica to the Arabian Desert, the Persian frontier blazed with action in a series of campaigns in which many of the generals later destined for fame in the West first demonstrated their capacities. The strength of the East Roman armies is revealed in the fact that, while containing Persian might, Justinian could nonetheless dispatch troops to attack the Huns in the Crimea and to maintain the Danubian frontier against a host of enemies. In 532 Justinian decided to abandon military operations in favour of diplomacy. He negotiated, at the cost of considerable tribute, an “Endless Peace” with the Persian king, Khosrow (Khosrow I), which freed the Roman's hands for operations in another quarter of the globe. Thus Justinian succeeded in attaining the first of the objectives needed for reconquest in the West: peace in the East.

Even before his accession, Justinian had aided in the attainment of the second. Shortly after his proclamation as emperor, Justin had summoned a council of bishops at Constantinople. The council reversed the policies of Anastasius, accepted the orthodox formula of Chalcedon, and called for negotiations with the pope. Justinian had personally participated in the ensuing discussions, which restored communion between Rome and all the Eastern churches save Egypt. No longer could a barbarian king hope to maintain the loyalties of his Catholic subjects by persuading them that a Monophysite emperor ruled in the East.

After 532 Justinian ruled more firmly than ever before. With the subsequent proclamation of the “Endless Peace,” he could hope to use his earlier won reputation as a champion of Chalcedonian orthodoxy and appeal to those Western Romans who preferred the rule of a Catholic Roman emperor to that of an Arian German kinglet. In these early years of the 530s, Justinian could indeed pose as the pattern of a Roman and Christian emperor. Latin was his language, and his knowledge of Roman history and antiquities was profound.

In 529 his officials had completed a major collection of the emperors' laws (Roman law) and decrees promulgated since the reign of Hadrian. Called the Codex Constitutionum and partly founded upon the 5th-century Theodosian Code, it comprised the first of four works compiled between 529 and 565 called the Corpus Juris Civilis (Body of Civil Law), commonly known as the Code of Justinian (Justinian, Code of). This first collection of imperial edicts, however, pales before the Digesta (Pandects) completed under Tribonian's direction in 533. In the latter work, order and system were found in (or forced upon) the contradictory rulings of the great Roman jurists; to facilitate instruction in the schools of law, a textbook, the Institutiones (533), was designed to accompany the Digesta. The fourth book, the Novellae Constitutiones Post Codicem (commonly called the Novels), consists of collections of Justinian's edicts promulgated between 534 and 565.

In 533 the moment had clearly come to reassert Christian Roman authority in the West, and Vandal North Africa seemed the most promising theatre of operations. Although a major expedition mounted under Leo I had failed to win back the province, political conditions in the Vandal monarchy had altered to the Eastern emperor's favour. When King Hilderich was deposed and replaced, Justinian could rightfully protest this action taken against a monarch who had ceased persecution of North African Catholics and had allied himself with Constantinople. The Eastern merchants favoured military action in the West, but Justinian's generals were reluctant; possibly for that reason, only a small force was dispatched under Belisarius. Success came with surprising ease after two engagements, and in 534 Justinian set about organizing this new addition to the provinces of the Roman Empire.

These were, in fact, years of major provincial reorganization, and not in North Africa alone. A series of edicts dated in 535 and 536, clearly conceived as part of a master plan by the prefect John of Cappadocia, altered administrative, judicial, and military structures in Thrace and Asia Minor. In general, John sought to provide a simplified and economical administrative structure in which overlapping jurisdictions were abolished, civil and military functions were sometimes combined in violation of Constantinian principles, and a reduced number of officials were provided with greater salaries to secure better personnel and to end the lure of bribery.

In the prefaces to his edicts, Justinian boasted of his reconstituted authority in North Africa, hinted at greater conquests to come, and—in return for the benefits his decrees were to provide—urged his subjects to pay their taxes promptly so that there might be “one harmony between ruler and ruled.” Quite clearly the Emperor was organizing the state for the most strenuous military effort, and, later (possibly in 539), reforms were extended to Egypt, whence the export of grain was absolutely essential for the support of expeditionary armies and Constantinople.

Developments during 534 and 535 in Ostrogothic Italy made it the most likely victim after the fall of Vandal North Africa. When Theodoric died in 526, he was succeeded by a minor grandson for whom Theodoric's daughter, Amalasuntha, acted as regent. Upon the boy's death, Amalasuntha attempted to seize power in her own right and connived at the assassination of three of her chief enemies. Her diplomatic relations with the Eastern emperor had always been marked by cordiality and even dependency; thus, when Amalasuntha, in turn, met her death in a blood feud mounted by the slain men's families, Justinian seized the opportunity to protest the murder.

In 535, as in 533, a small, tentative expedition sent to the West—in this instance, to Sicily—met with easy success. At first the Goths negotiated; then they stiffened their resistance, deposed their king, Theodahad, in favour of a stronger man, Witigis, and attempted to block Belisarius' armies as they entered the Italian peninsula. There the progress of East Roman arms proved slower, and victory did not come until 540 when Belisarius captured Ravenna, the last major stronghold in the north, and, with it, King Witigis, a number of Gothic nobles, and the royal treasure.

All were dispatched to Constantinople, where Justinian was presumably thankful for the termination of hostilities in the West. Throughout the 530s, Justinian's generals almost constantly had to fight to preserve imperial authority in the new province of North Africa and in the Balkans as well. In 539 a Gothic embassy reached Persia, and the information it provided caused the king, Khosrow (Khosrow I), to grow restive under the constraints of the “Endless Peace.” During the next year (the same year 【540】 that a Bulgar force raided Macedonia and reached the long walls of Constantinople), Khosrow's armies reached even Antioch in the pursuit of booty and blackmail. They returned unhurt, and 541 witnessed the Persian capture of a fortress in Lazica. In Italy, meanwhile, the Goths chose a new king, Totila, under whose able leadership the military situation in that land was soon to be transformed.

At last the menace of simultaneous war on two fronts threatened Justinian's plans. During the 550s, his armies were to prove equal to the challenge, but a major disaster prevented them from so doing between 541 and about 548. The disaster was the bubonic plague (Black Death) of 541–543, the first of those shocks, or traumas, mentioned earlier, that would eventually transform East Rome into the medieval Byzantine Empire. The plague was first noted in Egypt, and from there it passed through Syria and Asia Minor to Constantinople. By 543 it had reached Italy and Africa, and it may also have attacked the Persian armies on campaign in that year. In East Asia the disease has persisted into the 20th century, providing medical science with an opportunity to view its causes and course. Transmitted to humans by fleas from infected rodents, the plague attacks the glands and early manifests itself by swellings (buboes) in armpit and groin, whence the name bubonic. To judge from Procopius' description of its symptoms at Constantinople in 542, the disease then appeared in its more virulent pneumonic form, wherein the bacilli settle in the lungs of the victims. The appearance of the pneumonic form was particularly ominous because it may be transmitted directly from person to person, spreading the infection all the more readily and producing exceptionally high mortality rates. Comparative studies, based upon statistics derived from incidence of the same disease in late-medieval Europe, suggest that between one-third and one-half the population of Constantinople may well have died, while the lesser cities of the empire and the countryside by no means remained immune.

The short-term impact of the plague may be seen in several forms of human activity during the 540s. Justinian's legislation of those years is understandably preoccupied with wills and intestate succession. Labour was scarce, and workers demanded wages so high that Justinian sought to control them by edict, as the monarchs of France and England were to do during the plague of the 14th century. In military affairs, above all, the record of those years is one of defeat, stagnation, and missed opportunities. Rather than effective Roman opposition, it was Khosrow's own weariness of an unprofitable war that led him to sign a treaty of peace in 545, accepting tribute from Justinian and preserving Persian conquests in Lazica. Huns, Sclaveni, Antae, and Bulgars ravaged Thrace and Illyricum, meeting only slight opposition from Roman armies. In Africa a garrison diminished by plague nervously faced the threat of Moorish invasion. In Italy, Totila took the offensive, capturing southern Italy and Naples and even forcing his way into Rome (546) despite Belisarius' efforts to relieve the siege. Desperately, Justinian's great general called for reinforcements from the East; if ever they came, they were slow in arriving and proved numerically less than adequate to the task confronting them.

After about 548, Roman fortunes improved, and, by the mid-550s, Justinian had won victories in most theatres of operation, with the notable and ominous exception of the Balkans. A tour of the frontiers might begin with the East. In 551 the fortress of Petra was recovered from the Persians, but fighting continued in Lazica until a 50 years' peace, signed in 561, defined relations between the two great empires. On balance, the advantage lay with Justinian. Although Justinian agreed to continue payment of tribute in the amount of 30,000 solidi a year, Khosrow, in return, abandoned his claims to Lazica and undertook not to persecute his Christian subjects.

The treaty also regulated trade between Rome and Persia, since rivalry between the two great powers had always had its economic aspects, focused primarily upon the silk trade. Raw silk reached Constantinople through Persian intermediaries, either by a land route leading from China through Persia or by the agency of Persian merchants in the Indian Ocean. The need to break this Persian monopoly had led Justinian to search for new routes and new peoples to serve as intermediaries: in the south, the Ethiopian merchants of the kingdom of Aksum; in the north, the peoples around the Crimea and in the Caucasian kingdom of Lazica, as well as the Turks of the steppes beyond the Black Sea. Other valuable commodities were exchanged in the Black Sea region, including textiles, jewelry, and wine from East Rome for the furs, leather, and slaves offered by the barbarians; yet, silk remained the commodity of prime interest. It was fortunate, then, that before 561, East Roman agents had smuggled silkworms from China into Constantinople, establishing a silk industry that would liberate the empire from dependence on Persia and become one of medieval Byzantium's most important economic operations.

In the West, Justinian's successes were even more spectacular. By 550 the Moorish threat had ended in North Africa. In 552 the armies of Justinian had intervened in a quarrel among the Visigothic (Visigoth) rulers of Spain, and the East Roman troops overstayed the invitation extended them, seizing the opportunity to occupy on a more permanent basis certain towns in the southeastern corner of the Iberian Peninsula. Most important of all, Italy was recovered. Early in the 550s, Justinian assembled a vast army composed not only of Romans but also of barbarians, including Lombards, Heruli, and Gepids, as well as Persian deserters. Command of this host eventually was given to an unlikely but, as events were to prove, able commander: the eunuch and chamberlain Narses. In two decisive battles (Busta Gallorum and Mons Lactarius), the East Roman general defeated first Totila and then his successor, Teias. The Goths agreed to leave Italy. Despite the continued resistance of certain Gothic garrisons, coupled with the intervention of Franks and Alamanni, after 554 the land was essentially a province of the East Roman Empire.

In view of the wide mixture of peoples that descended upon it, the Balkans present a far more complex situation, and the Romans used a wider variety of tactics to contain the barbarians. After the Kutrigur Bulgar attack of 540, Justinian worked to extend a system of fortifications that ran in three zones through the Balkans and as far south as the Pass of Thermopylae. Fortresses, strongholds, and watchtowers were not, however, enough. The Slavs plundered Thrace in 545 and returned in 548 to menace Dyrrhachium; in 550 the Sclaveni, a Slavic people, reached a point about 40 miles (65 kilometres) from Constantinople. The major invasion came in 559, when the Kutrigur Bulgars, accompanied by Sclaveni, crossed the Danube and divided their force into three columns. One column reached Thermopylae; the second gained a foothold on the Gallipoli Peninsula near Constantinople; and the third advanced as far as the suburbs of Constantinople itself, which the aged Belisarius had to defend with an unlikely force of civilians, demesmen, and a few veterans. Worried by Roman naval action on the Danube, which seemed to menace the escape route home, the Kutrigurs broke off the attack, returned north, and found themselves under attack from the Utigurs, a people whose support Justinian's agents had earlier connived at and won by suitable bribes. The two peoples weakened each other in warfare, of which the episode of 559 was not the first instance, and this was precisely the result at which Byzantine diplomacy was aimed.

As long as the financial resources remained adequate, diplomacy proved the most satisfactory weapon in an age when military manpower was a scarce and precious commodity. Justinian's subordinates were to perfect it in their relationships with Balkan and south Russian peoples. For, if the Central Asian lands constituted a great reservoir of people, whence a new menace constantly emerged, the very proliferation of enemies meant that one might be used against another through skillful combination of bribery, treaty, and perfidy. East Roman relations in the late 6th century with the Avars (Avar), a Mongol people seeking refuge from the Turks, provide an excellent example of this “defensive imperialism.” The Avar ambassadors reached Constantinople in 557, and, although they did not receive the lands they demanded, they were loaded with precious gifts and allied by treaty with the empire. The Avars moved westward from south Russia, subjugating Utigurs, Kutrigurs, and Slavic peoples to the profit of the empire. At the end of Justinian's reign, they stood on the Danube, a nomadic people hungry for lands and additional subsidies and by no means unskilled themselves in a sort of perfidious diplomacy that would help them pursue their objectives.

No summary of the quiet, but ominous, last years of Justinian's reign would be complete without some notice of the continuing attacks of bubonic plague (Black Death) and the impact they were to continue to produce until the 8th century. As have other societies subjected to devastation from warfare or disease, East Roman society might have compensated for its losses of the 540s had the survivors married early and produced more children in the succeeding generations. Two developments prevented recovery. Monasticism, with its demands for celibacy, grew apace in the 6th century, and the plague returned sporadically to attack those infants who might have replaced fallen members of the older generations.

The resulting shortage of manpower affected several aspects of a state and society that perceptibly were losing their Roman character and assuming their Byzantine. The construction of new churches, so noteworthy a feature of the earlier years, ceased as men did little more than rebuild or add to existing structures. An increasing need for taxes, together with a decreasing number of taxpayers, evoked stringent laws that forced members of a village tax group to assume collective responsibility for vacant or unproductive lands. This, contemporary sources avow, was a burden difficult to assume, in view of the shortage of agricultural workers after the plague. Finally, the armies that won the victories described above in east and west were largely victorious only because Justinian manned them as never before with barbarians: Goths, Armenians, Heruli, Gepids, Saracens, and Persians—to name only the most prominent. It was far from easy to maintain discipline among so motley an army; yet, once the unruly barbarian accepted the quieter life of the garrison soldier, he tended to lose his fighting capacity and prove, once the test came, of little value against the still warlike barbarian facing him beyond the frontier. The army, in short, was a creation of war and kept its quality only by participating in battlefield action, but further expansive warfare could hardly be undertaken by a society chronically short of men and money.

In summary, the East Roman (or better, the Byzantine) state of the late 6th century seemed to confront many of the same threats that had destroyed the Western Empire in the 5th century. Barbarians pressed upon it from beyond the Balkan frontier, and peoples of barbarian origin manned the armies defending it. Wealth accumulated during the 5th century had been expended; and, to satisfy the basic economic and military needs of state and society, there were too few native Romans. If the Byzantine Empire avoided the fate of West Rome, it did so only because it was to combine valour and good luck with certain advantages of institutions, emotions, and attitudes that the older empire had failed to enjoy. One advantage already described, diplomatic skill, blends institutional and attitudinal change, for diplomacy would never have succeeded had not the Byzantine statesmen been far more curious and knowing than Justinian's 5th-century predecessor about the habits, customs, and movements of the barbarian peoples. The Byzantine's attitude had changed in yet another way. He was willing to accept the barbarian within his society provided that the latter, in his turn, accept orthodox Christianity and the emperor's authority. Christianity was often, to be sure, a veneer that cracked in moments of crisis, permitting a very old paganism to emerge, while loyalty to the emperor could be forsworn and often was. Despite these shortcomings, the Christian faith and the ecclesiastical institutions defined in the 6th century proved better instruments by far to unite men and stimulate their morale than the pagan literary culture of the Greco-Roman world.

Justinian regulated the size of churches and monasteries, forbade them to profit from the sale of property, and complained of those priests and bishops who were unlearned in the forms of the liturgy. His efforts to improve the quality of the secular clergy, or those who conducted the affairs of the church in the world, were most opportune. The best possible men were needed, for, in most East Roman cities during the 6th century, imperial and civic officials gradually resigned many of their functions to the bishop, or patriarch. The latter collected taxes, dispensed justice, provided charity, organized commerce, negotiated with barbarians, and even mustered the soldiers. By the early 7th century, the typical Byzantine city, viewed from without, actually or potentially resembled a fortress; viewed from within, it was essentially a religious community under ecclesiastical leadership. Nor did Justinian neglect the monastic (monasticism) clergy, or those who had removed themselves from the world. Drawing upon the regulations to be found in the writings of the 4th-century Church Father St. Basil of Caesarea, as well as the acts of 4th- and 5th-century church councils, he ordered the cenobitic (or collective) form of monastic life in a fashion so minute that later codes, including the rule of St. Theodore the Studite in the 9th century, only develop the Justinianic foundation.

Probably the least successful of Justinian's ecclesiastical policies were those adopted in an attempt to reconcile Monophysites and orthodox Chalcedonians. After the success of negotiations that had done so much to conciliate the West during the reign of Justin I, Justinian attempted to win over the moderate Monophysites, separating them from the extremists. Of the complicated series of events that ensued, only the results need be noted. In developing a creed acceptable to the moderate Monophysites of the East, Justinian alienated the Chalcedonians of the West and thus sacrificed his earlier gains in that quarter. The extreme Monophysites refused to yield. Reacting against Justinian's persecutions, they strengthened their own ecclesiastical organization, with the result that many of the fortress cities noted above, especially those of Egypt and Syria, owed allegiance to Monophysite ecclesiastical leadership. To his successors, then, Justinian bequeathed the same religious problem he had inherited from Anastasius.

If, in contrast, his regulation of the Christian life proved successful, it was largely because his subjects themselves were ready to accept it. Traditional Greco-Roman culture was, to be sure, surprisingly tenacious and even productive during the 6th century and was always to remain the treasured possession of an intellectual elite in Byzantium; but the same century witnessed the growth of a Christian culture to rival it. Magnificent hymns (hymn) written by St. Romanos Melodos mark the striking development of the liturgy (liturgical music) during Justinian's reign, a development that was not without its social implications. Whereas traditional pagan culture was literary and its pursuit or enjoyment thereby limited to the leisured and wealthy, the Christian liturgical celebration and its musical component were available to all, regardless of place or position. biography, too, became both markedly Christian and markedly popular. Throughout the countryside and the city, holy men appeared in legend or in fact, exorcising demons, healing the sick, feeding the hungry, and warding off the invader. Following the pattern used in the 4th century by Athanasius to write the life of St. Anthony, hagiographers (hagiography) recorded the deeds of these extraordinary men, creating in the saint's life a form of literature that began to flower in the 6th and 7th centuries.

The vitality and pervasiveness of popular Christian culture manifested themselves most strongly in the veneration increasingly accorded the icon (iconography), an abstract and simplified image of Christ, the Virgin, or the saints. Notable for the timeless quality that its setting suggested and for the power expressed in the eyes of its subject, the icon seemingly violated the Second Commandment's explicit injunction against the veneration of any religious images. Since many in the early centuries of the church so believed, and in the 8th century the image breakers, or iconoclasts (Iconoclastic Controversy), were to adopt similar views, hostility toward images was nearly as tenacious an aspect of Christianity as it had been of Judaism before it.

The contrasting view—a willingness to accept images as a normal feature of Christian practice—would not have prevailed had it not satisfied certain powerful needs as Christianity spread among Gentiles long accustomed to representations of the divinity and among Hellenized Jews who had themselves earlier broken with the Mosaic commandment. The convert all the more readily accepted use of the image if he had brought into his Christianity, as many did, a heritage of Neoplatonism. The latter school taught that, through contemplation of that which could be seen (i.e., the image of Christ), the mind might rise to contemplation of that which could not be seen (i.e., the essence of Christ). From a belief that the seen suggests the unseen, it is but a short step to a belief that the seen contains the unseen and that the image deserves veneration because divine power somehow resides in it.

Men of the 4th century were encouraged to take such a step, influenced as they were by the analogous veneration that the Romans had long accorded the image of the emperor. Although the first Christians rejected this practice of their pagan contemporaries and refused to adore the image of a pagan emperor, their successors of the 4th century were less hesitant to render such honour to the images of the Christian emperors following Constantine. Since the emperor was God's vicegerent on Earth and his empire reflected the heavenly realm, the Christian must venerate, to an equal or greater degree, Christ and his saints. Thus the Second Commandment finally lost much of its force. Icons appeared in both private and public use during the last half of the 6th century: as a channel of divinity for the individual and as a talisman to guarantee success in battle. During the dark years following the end of Justinian I's reign, no other element of popular Christian belief better stimulated that high morale without which the Byzantine Empire would not have survived.

The accession of Maurice in 582 inaugurated a reign of 20 years marked by success against Persia, a reorganization of Byzantine government in the West, and the practice of economies during his Balkan campaigns that, however unavoidable, would destroy him in 602. Byzantine efforts against Sāsānian Persia were rewarded in 591 by a fortunate accident. The lawful claimant to the Persian throne, Khosrow II, appealed to Maurice for aid against the rebels who had challenged his succession. In gratitude for this support, Khosrow abandoned the frontier cities and the claims to Armenia, the two major sources of contention between Byzantium and Persia. The terms of the treaty gave Byzantium access, in Armenia, to a land rich in the soldiers it desperately needed and, equally important, an opportunity to concentrate on other frontiers where the situation had worsened.

Confronted by a Visigothic resurgence in Spain and by the results of a Lombard invasion of Italy (568), which was steadily confining Byzantine power to Ravenna, Venice, and Calabria-Sicily in the south, Maurice developed a form of military government throughout the relatively secure province of North Africa and in whatever regions were left in Italy. He abandoned the old principle of separating civil from military powers, placing both in the hands of the generals, or exarchs, located, respectively, at Carthage and Ravenna. Their provinces, or exarchates, were subdivided into duchies composed of garrison centres that were manned not by professional soldiers but by conscript local landholders. The exarchate system of military government seems to have worked well: North Africa was generally quiet despite Moorish threats; and in 597 the ailing Maurice had intended to install his second son as emperor throughout those western possessions in which he had clearly not lost interest.

But the major thrust of his efforts during the last years of his reign was to be found in the Balkans, where, by dint of constant campaigning, his armies had forced the Avars back across the Danube by 602. In the course of these military operations, Maurice made two mistakes: the first weakened him; the second destroyed him together with his dynasty. Rather than constantly accompanying his armies in the field, as his 7th- and 8th-century successors were to do, Maurice remained for the most part in Constantinople, losing an opportunity to engage the personal loyalty of his troops. He could not count on their obedience when he issued unwelcome commands from afar that decreased their pay in 588, ordered them to accept uniforms and weapons in kind rather than in cash equivalents, and, in 602, required the soldiers to establish winter quarters in enemy lands across the Danube, lest their requirements prove too great a strain on the agricultural and financial resources of the empire's provinces south of the river. Exasperated by this last demand, the soldiers rose in revolt, put a junior officer named Phocas at their head, and marched on Constantinople. Again becoming politically active, the Blues and Greens united against Maurice, and the aged emperor watched as his five sons were slaughtered before he himself met a barbarous death.

The ensuing reign of Phocas (602–610) may be described as a disaster. Khosrow seized the opportunity offered him by the murder of his benefactor, Maurice, to initiate a war of revenge that led Persian armies into the Anatolian heartland. Subsidies again failed to restrain the barbarians north of the Danube; after 602 the frontier crumbled, not to be restored save at the cost of centuries of warfare. Lacking a legitimate title, holding his crown only by right of conquest, Phocas found himself confronted by constant revolt and rebellion. To contemporaries, the coincidence of pestilence, endemic warfare, and social upheaval seemed to herald the coming of the Antichrist, the resurrection of the dead, and the end of the world.

But it was a human saviour who appeared, albeit under divine auspices. Heraclius, son of the Exarch of Africa, set sail from the western extremes of the empire, placing his fleet under the protection of an icon of the Virgin against Phocas, stigmatized in the sources as the “corrupter of virgins.” In the course of his voyage along the northern shores of the Mediterranean, Heraclius added to his forces and arrived at Constantinople in October 610 to be hailed as a saviour. With the warm support of the Green faction, he quickly bested his enemy, decapitating Phocas and, with him, those Phocas had advanced to high civil and military office. There were, in consequence, few experienced counselors to aid Heraclius, for, among the men of prominence under Phocas—and earlier under Maurice—few survived to greet the new emperor.

Three sources of strength enabled Heraclius to turn defeat into victory. The first was the pattern of military government as he and the nucleus of his army would have known it in the exarchates of North Africa or Ravenna. As it had been in the West, so it now was in the East. Civil problems were inseparable from the military: Heraclius could not hope to dispense justice, collect taxes, protect the church, and assure the future to his dynasty unless military power reinforced his orders. A system of military government, the exarchate, had accomplished these objectives so well in the West that, in a moment of despair, Heraclius sought to return to the land of his origins. In all likelihood, he applied similar principles of military rule to his possessions throughout Asia Minor, granting his generals (stratēgoi) both civil and military authority over those lands that they occupied with their “themes (theme),” as the army groups, or corps, were called in the first years of the 7th century.

Second, during the social upheaval of the previous decade, the imperial treasury had doubtless seized the estates of prominent individuals who had been executed either during Phocas' reign of terror or after his death. In consequence, though the treasury lacked money, it nonetheless possessed land in abundance, and Heraclius could easily have supported with grants of land those cavalry soldiers whose expenses in horses and armament he could not hope to meet with cash. If this hypothesis is correct, then, even before 622, themes, or army groups—including the guards (Opsikioi), the Armenians (Armeniakoi), and the Easterners (Anatolikoi)—were given lands and settled throughout Asia Minor in so permanent a fashion that, before the century was out, the lands occupied by these themes were identified by the names of those who occupied them. The Opsikioi were to be found in the Opsikion theme, the Armeniakoi in the Armeniakon, and the Anatolikoi in the Anatolikon. The term theme ceased thereafter to identify an army group and described instead the medieval Byzantine unit of local administration, the theme under the authority of the themal commander, the general (stratēgos).

When Heraclius “went out into the lands of the themes” in 622, thereby undertaking a struggle of seven years' duration against the Persians, he utilized the third of his sources of strength: religion. The warfare that ensued was nothing less than a holy war: it was partly financed by the treasure placed by the church at the disposal of the state; the Emperor's soldiers called upon God to aid them as they charged into battle; and they took comfort in the miraculous image of Christ that preceded them in their line of march. A brief summary of the campaign unfortunately gives no idea of the difficulties Heraclius encountered as he liberated Asia Minor (622); fought in Armenia with allies found among the Christian Caucasian peoples, the Lazi, the Abasgi, and the Iberians (624); and struggled in far-distant Lazica while Constantinople withstood a combined siege of Avars and Persians (626). An alliance with the Khazars (Khazar), a Turkic people from north of the Caucasus, proved of material assistance in those years and of lasting import in Byzantine diplomacy. Heraclius finally destroyed the main Persian host at Nineveh in 627 and, after occupying Dastagird in 628, savoured the full flavour of triumph when his enemy, Khosrow, was deposed and murdered. The Byzantine emperor might well have believed that, if the earlier success of the Persians signalized the resurrection of the Achaemenid Empire, his own successes had realized the dreams of Caesar, Augustus, and Trajan.

Yet this was a war fought by medieval Byzantium and not by ancient Rome. Its spirit was manifest in 630, when Heraclius triumphantly restored the True Cross to Jerusalem, whence the Persians had stolen it, and—even more—when Constantinople resisted the Avar–Persian assault of 626. During the attack, the patriarch Sergius maintained the morale of the valiant garrison by proceeding about the walls, bearing the image of Christ to ward off fire, and by painting upon the gates of the western walls images of the Virgin and child to ward off attacks launched by the Avars—the “breed of darkness.” The Avars withdrew when Byzantine ships defeated the canoes manned by Slavs, upon whom the nomad Avars depended for their naval strength. The latter never recovered from their defeat. As their empire crumbled, new peoples from the Black Sea to the Balkans emerged to seize power: the Bulgars of Kuvrat, the Slavs under Samo, and the Serbs and Croats whom Heraclius permitted to settle in the northwest Balkans once they had accepted Christianity.

As for the Byzantine defenders of Constantinople, they celebrated their victory by singing Romanos' great hymn “Akathistos,” with choir and crowd alternating in the chant of the “Alleluia.” The hymn, still sung in a Lenten service, commemorates those days when Constantinople survived as a fortress under ecclesiastical leadership, its defenders protected by the icons and united by their liturgy. This they sang in Greek, as befitted a people whose culture was now Greek and no longer Latin.

In the same year that Heraclius went out into the themes, Muḥammad (Muhammad) made his withdrawal (hijrah) from Mecca to Medina, where he established the ummah, or Muslim (Islāmic world) community. Upon the Prophet's death in 632, the caliphs, or successors, channeled the energies of the Arab Bedouin by launching them upon a purposive and organized plan of conquest. The results were spectacular: a Byzantine army was defeated at the Battle of the Yarmūk River (636), thereby opening Palestine and Syria to Arab Muslim control. Alexandria capitulated in 642, removing forever the province of Egypt from Byzantine authority. The Arabs had, meanwhile, advanced into Mesopotamia, capturing the royal city of Ctesiphon and, eventually, defeating an army under command of the Persian king himself. So ended the long history of Persia under Achaemenids, Parthians, and Sāsānians; further conquests were shortly to initiate that region's Islāmic phase (see further Iran, history of: Iran from 640 to the present (Iran); Islāmic world).

At least three aspects of the contemporary situation of Byzantium and Persia account for the phenomenal ease with which the Arabs overcame their enemies: first, both empires, exhausted by wars, had demobilized before 632; second, both had ceased to support those client states on the frontiers of the Arabian Peninsula that had restrained the Bedouin of the desert for a century past; third, and particularly in reference to Byzantium, religious controversy had weakened the loyalties that Syrians and Egyptians rendered to Constantinople. Heraclius had sought in 638 to placate Monophysite sentiment in these two provinces by promulgating the doctrine of Monothelitism (Monothelite), holding that Christ, although of two natures, had but one will. Neither in the East nor in the West did this compromise prove successful. The victorious Muslims granted religious freedom to the Christian community in Alexandria, for example, and the Alexandrians quickly recalled their exiled Monophysite patriarch to rule over them, subject only to the ultimate political authority of the conquerors. In such a fashion the city persisted as a religious community under an Arab Muslim domination more welcome and more tolerant than that of Byzantium.

Three features distinguish the military history of the years 641–717: first, an increasing use of sea power on the part of the Arabs; second, a renewed threat in the Balkans occasioned by the appearance of the Onogur Huns, known in contemporary sources as the Bulgars; third, a persisting interest among the emperors in their western possessions, despite the gradual attrition of Byzantine authority in the exarchates of Carthage and Ravenna. Thanks to the control that the Arabs gradually asserted over the sea routes to Constantinople, they climaxed their earlier assaults on Armenia and Asia Minor with a four years' siege of the great city itself (674–678). Defeated in this last attempt by the use of Greek fire, a flammable liquid of uncertain composition, the Arabs signed a 30 years' truce, according to which they agreed to pay tribute in money, men, and horses. Lured by the unsettled conditions following Justinian's second deposition, they renewed their assaults by land and sea, and in 717 the Arabs were again besieging Constantinople.

On the Balkan frontier, meanwhile, the Bulgars assumed the role abdicated by the Avars (Avar) after 626. A pagan people whom the Khazars had forced toward the Danube Delta in the latter part of the 7th century, they eluded Constantine IV's attempts to defeat them in 681. By virtue of a treaty signed in that year, as well as others dating from 705 and 716, the Bulgars were recognized as an independent kingdom, occupying (to the humiliation of Byzantium) lands south of the Danube into the Thracian plain. While the Bulgars had thus deprived the empire of control in the north and central Balkans, the Byzantines could take comfort in the expeditions of 658 and 688/689 launched, respectively, by Constans II and Justinian II into Macedonia and in the formation of the themes of Thrace (687) and Hellas (695); these moves were evidence that Byzantine authority was beginning to prevail along the peninsular coastline and in certain parts of Greece where Slavs had penetrated.

In the West, the situation was less reassuring. Monothelitism had evoked a hostile reception among the churches of North Africa and Italy, and the resulting disaffection had encouraged the exarchs of both Carthage (646) and Ravenna (652) to revolt. By the end of the century, Africa had been largely lost to Muslim conquerors who would, in 711, seize the last outpost at Septem. For the moment Sicily and the scattered Italian possessions remained secure. Constans undertook operations against the Lombards, and he apparently intended to move his capital to Sicily, before his assassination ended the career of the last Eastern emperor to venture into the West. In summary, Leo III in 717 ruled over an empire humiliated by the presence of pagan barbarians upon Balkan soil rightfully considered “Roman,” threatened by an attack upon its Anatolian heartland and its capital, and reduced, finally, in the West to Sicily and the remnants of the Ravenna exarchate.

However dismal the military record, institutional and economic developments had permitted the empire to survive and were to provide foundations for greater success in the centuries to come. The themal system had taken root and, with it, probably the institution of soldiers' properties. Military service was a hereditary occupation: the eldest son assumed the burden of service, supported primarily by revenues from other members of the family who worked the land in the villages. This last was a task easier to accomplish at the end of the 7th century thanks to the colonies of Slavs and other peoples brought into the empire and settled in the rural areas by Heraclius, Constantine IV, and Justinian II. In the 8th and 9th centuries, other emperors, including Leo III, Constantine V, and Nicephorus I, were to continue the practice, thus ending the population decline that had long eroded the ranks of Byzantine society. There are unmistakable signs of agricultural expansion even before 800; and, at about that time, urban life, which had never vanished in Asia Minor, began to flourish and expand in the Balkans. To judge from the evidence of the Farmer's Law, dated in the 7th century, the technological base of Byzantine society was more advanced than that of contemporary western Europe: iron tools could be found in the villages; water mills dotted the landscape; and field-sown beans provided a diet rich in protein. None of these advances was to characterize western European agriculture until the 10th century. Byzantine agriculture enjoyed the further advantage of a highly developed tradition of careful farming that persisted even in the darkest days, enabling the peasant to make the most of the soil upon which he worked. The invasions had even provided a form of stimulus to development: having lost first its Egyptian granary and, later, its North African and Sicilian resources, the empire had to live essentially, although not totally, from whatever it could produce in the lands remaining to it. The invasions had also, in all probability, broken up many a large estate, and the small peasant holding seems to have been the “normal” form of rural organization in this period. Although collective village organization persisted in the form of the rural commune and, with it, certain collective agricultural practices, the state seems to have made little or no attempt to bind the peasant to the soil upon which the tax registers had inscribed him. While Byzantium remained a slave-owning society, the colonus of the later Roman Empire had vanished, and a greater degree of freedom and mobility characterized agricultural relationships during the 7th and 8th centuries.

So it was, too, in trade and commerce. After the loss of Egypt and North Africa, the grain fleets manned by hereditary shipmasters disappeared; in their place there emerged the independent merchant, of sufficient importance to call forth a code of customary law, the Rhodian Sea Law, to regulate his practices. Military and religious hostilities failed to check him as he traded with the Bulgars in Thrace and, through Cyprus, with the Arabs. Despite constant warfare, this was, in short, a healthier society than the late Roman, and its chances of survival were further increased when the sixth general council (680–681) condemned Monothelitism and anathematized its adherents. With Egypt and Syria under Muslim rule, it was no longer necessary to placate Eastern Monophysitism, and it seemed that doctrinal discord would no longer separate Constantinople from the West. Events were to prove otherwise.

In later centuries, the folk of Constantinople would stand by his tomb, seeking his aid against whatever enemy imperiled the city's defenses.

His successors all but let slip the gains won by the great iconoclast. Constantine's son Leo IV died prematurely in 780, leaving to succeed him his 10-year-old son, Constantine VI, under the regency of the empress Irene. Not much can be said for Constantine, and Irene's policies as regent and (after the deposition and blinding of her son at her orders) as sole ruler from 797 to 802 were all but disastrous. Her iconodule policies alienated many among the themal troops, who were still loyal to the memory of the great warrior emperor, Constantine V. In an effort to maintain her popularity among the monkish defenders of the icons and with the population of Constantinople, she rebated taxes to which these groups were subject; she also reduced the customs duties levied outside the port of Constantinople, at Abydos and Hieros. The consequent loss to the treasury weighed all the more severely since victories won by the Arabs in Asia Minor (781) and by the Bulgars (792) led both peoples to demand and receive tribute as the price of peace. A revolt of the higher palace officials led to Irene's deposition in 802, and the so-called Isaurian dynasty of Leo III ended with her death, in exile, on the isle of Lesbos.

In the face of the Bulgar menace, none of the following three emperors succeeded in founding a dynasty. Nicephorus I (ruled 802–811), the able finance minister who succeeded Irene, reimposed the taxes that the Empress had remitted and instituted other reforms that provide some insight into the financial administration of the empire during the early 9th century. In the tradition of Constantine V, Nicephorus strengthened the fortifications of Thrace by settling, in that theme, colonists from Asia Minor.

Taking arms himself, he led his troops against the new and vigorous Bulgar khan, Krum, only to meet defeat and death at the latter's hands. His successor, Michael I Rhangabe (811–813), fared little better; internal dissensions broke up his army as it faced Krum near Adrianople, and the resulting defeat cost Michael his throne. In only one respect does he occupy an important place in the annals of the Byzantine Empire. The first emperor to bear a family name, Michael's use of the patronymic, Rhangabe, bears witness to the emergence of the great families, whose accumulation of landed properties would soon threaten the integrity of those smallholders upon whom the empire depended for its taxes and its military service. The name Rhangabe seems to be a Hellenized form of a Slav original (rokavu), and, if so, Michael's ethnic origin and that of his successor, Leo V the Armenian (ruled 813–820), provide evidence enough of the degree to which Byzantium in the 9th century had become not only a melting-pot society but, further, a society in which even the highest office lay open to the man with the wits and stamina to seize it. Leo fell victim to assassination, but before his death events beyond his control had improved the empire's situation. Krum died suddenly in 814 as he was preparing an attack upon Constantinople, and his son, Omortag, arranged a peace with the Byzantine Empire in order to protect the western frontiers of his Bulgar empire against the pressures exerted by Frankish expansion under Charlemagne and his successors. Since the death of the fifth caliph, Hārūn ar-Rashīd, had resulted in civil war in the Muslim world, hostilities from that quarter ceased. Leo used the breathing space to reconstruct those Thracian cities that the Bulgars had earlier destroyed. His work indicates the degree of gradual Byzantine penetration into the coastal fringes of the Balkan Peninsula, as does the number of themes organized in that same region during the early 9th century: those of Macedonia, Thessalonica, Dyrrhachium, Dalmatia, and the Strymon.

The new emperor, Michael II, was indeed able to establish a dynasty—the Amorian, or Phrygian—his son Theophilus (829–842) and his grandson Michael III (842–867) each occupying the throne in turn, but none would have forecast so happy a future during Michael II's first years. Thomas the Slavonian, Michael's former comrade in arms, gave himself out to be the unfortunate Constantine VI and secured his coronation at the hands of the Patriarch of Antioch; this was accomplished with the willing permission of the Muslim caliph under whose jurisdiction Antioch lay. Thomas thereupon marched to Constantinople at the head of a motley force of Caucasian peoples whose sole bonds were to be found in their devotion to iconodule doctrine and their hatred of Michael's Iconoclasm. Assisted by Omortag and relying upon the defenses of Constantinople, Michael defeated his enemy, but the episode suggests the tensions beneath the surface of Byzantine society: the social malaise, the ethnic hostility, and the persisting discord created by Iconoclasm. All these may explain the weakness displayed throughout Theophilus' reign, when a Muslim army defeated the Emperor himself (838) as a prelude to the capture of the fortress of Amorium in Asia Minor. It may also explain the concurrent decline of Byzantine strength in the Mediterranean, manifest in the capture of Crete by the Arabs (826 or 827) and in the initiation of attacks upon Sicily that finally secured the island for the world of Islām. Iconoclasm certainly played its part in the further alienation of East from West, and a closer examination of its doctrines will suggest why this may have been.

Iconoclasts and iconodules agreed on one fundamental point: a Christian people could not prosper unless it assumed the right attitude toward the holy images, or icons. They disagreed, of course, on what that attitude should be. Each could discover supporting arguments in the writings of the early church, and it is essential to remember that the debate over images is as old as Christian art. The fundamentals of Iconoclasm were by no means an 8th-century discovery. The ablest defender of the iconodule position was, however, the 8th-century theologian St. John of Damascus (John of Damascus, Saint). Drawing upon Neoplatonic doctrine, John suggested that the image was but a symbol; the creation of the icon was justified since, by virtue of the Incarnation, God had himself become man.

The iconoclasts responded by pointing to the express wording of the Second Commandment. The condemnation therein of idolatry seems to have weighed heavily with Leo III, who may have been influenced by Islām, a religion that strictly prohibited the use of religious images. The latter point is debatable, as is the contention that Iconoclasm was particularly an expression of sentiment to be found in the eastern themes of the empire. There is little doubt, however, that Monophysitism (monophysite) influenced the ideas of Constantine V and, through him, the course of debate during the last half of the 8th century. In the eyes of the Monophysite, who believed in the single, indistinguishable, divine nature of Christ, the iconodule was guilty of sacrilege. Either he was a Nestorian, reducing the divine nature to human terms in the image, or he was a Chalcedonian Dyophysite, radically distinguishing that which man could not distinguish. Still another consideration favouring Iconoclasm may be found in the intimate connection of iconoclastic doctrine with the emperor's conception of his role as God's vicegerent on Earth. During the late 6th and 7th centuries, iconodule emperors had viewed themselves in a pietistic fashion, emphasizing their devotion and subservience to God. Constantine V, on the other hand, pridefully replaced the icons with imperial portraits and with representations of his own victories. Viewed in this light, Iconoclasm signaled a rebirth of imperial confidence; so deservedly great was Constantine's reputation, and so dismal were the accomplishments of his successors, that a Leo V, for one, could easily believe that God favoured the iconoclastic battalions.

Under Constantine V, the struggle against the icons became a struggle against their chief defenders, the monastic community. The immediate destruction wrought by Constantine and his zealous subordinates is, however, of less moment than the lasting effect of the persecution on the Orthodox clergy. Briefly put, the church became an institution rent by factions, wherein popular discontent found a means of expression. Intransigent iconodules looked for their leaders among the monks of Studion, the monastery founded by Studius, and they found one in the person of the monastery's abbot, St. Theodore Studites (Theodore Studites, Saint) (759–826). In the patriarch Ignatius (847–858; 867–877) they discovered a spokesman after their own hearts: one drawn from the monastic ranks and contemptuous of all the allurements that the world of secular learning seemed to offer. More significant than the men to be found on the other extreme, iconoclast patriarchs, including Anastasius and John Grammaticus, were the representatives of the moderate party, composed of the patriarchs Tarasius, Nicephorus, Methodius, and Photius. Although iconodule in sympathy, the group enjoyed little rapport with the monastic zealots. Unlike the average monk, they were often educated laymen, trained in the imperial service and ready to compromise with imperial authority.

Not only was Iconoclasm a major episode in the history of the Byzantine, or Orthodox, Church, but it also permanently affected relations between the empire and Roman Catholic Europe. The Lombard advance, it may be remembered, had restricted Byzantine authority in Italy to the Exarchate of Ravenna, and to that quarter the popes of the 7th century, themselves ordinarily of Greek or Syrian origin, turned for protection against the common enemy. During the 8th century, two issues alienated Rome from Constantinople: Iconoclasm and quarrels stemming from the question of who should enjoy ecclesiastical jurisdiction over Illyricum and over Calabria in southern Italy. Pope Gregory II (Gregory II, Saint) refused to accept the iconoclastic doctrines of Leo III; and his successor, Gregory III (Gregory III, Saint), had openly to condemn them at a council. Once Ravenna fell to the Lombards, and the exarchate ceased to exist in 751, the papacy had to seek a new protector. This was found in the person of the Frankish leader Pippin III, who sought some form of sanction to legitimize his seizure of the crown from the feeble hands of the last representative of the Merovingian dynasty. Thus Pope Stephen II (Stephen II (or III)) (or III) anointed Pippin as king of the Franks in 754, and the latter entered Italy to take arms against the Lombard king. Even the restoration of icon veneration in 787 failed to bridge the differences between Orthodox Byzantium and Catholic Europe, for the advisers of Pippin's son and successor, Charlemagne, condemned the iconodule position as heartily as an earlier generation had rejected the iconoclast decrees of Leo III. Nor could the men of Charlemagne's time admit that a woman—the empress Irene—might properly assume the dignity of emperor of the Romans. For all these reasons, Charlemagne, king of the Franks and Lombards (Lombard) by right of conquest, assented to his coronation as emperor of the Romans on Christmas Day, 800, by Pope Leo III. No longer a barbarian king, Charlemagne became, by virtue of the symbolism of the age, a new Constantine. This the Byzantine chancery could not accept, for, if there were one God, one faith, and one truth, then there could be but one empire and one emperor; surely that emperor ruled in Constantinople, not in Charlemagne's Aachen. Subsequent disputes between Rome and Constantinople seemed often to centre upon matters of ecclesiastical discipline; underlying these differences were two more powerful considerations, neither of which could be ignored. According to theory there could be but one empire; clearly, there were two. And between Rome and Constantinople there stood two groups of peoples open to conversion: the Slavs of central Europe and the Bulgars in the Balkans. From which of the two jurisdictions would these people accept their Christian discipline? To which, in consequence, would they owe their spiritual allegiance?

The reign of Michael III (ruled 842–867) draws together these and other threads from the past. Veneration of the icons was definitely rehabilitated in 843; and it was done in so diplomatic a fashion that the restoration, in itself, produced no new rifts, although old factionalisms persisted with the appointment of a monk, Ignatius, as patriarch. The latter's intransigent zealotry found little favour with Caesar Bardas, Michael's uncle, who had seized power from the Empress Regent in 856. Two years later Ignatius was deposed and replaced by a moderate: the scholar and layman Photius (Photius, Saint). No single person better exemplified the new age, nor, indeed, did any other play a larger part in the cultural rebirth and missionary activity among the Slavs, Bulgars, and Russians, which mark the middle of the 9th century. The same aggressive and enterprising spirit is manifest in the military successes won on the Asia Minor frontier, culminating in Petronas' victory at Poson (863) over the Muslim emir of Melitene.

In Sicily, and throughout the Mediterranean, Byzantine arms were less successful, but, thanks to Photius' diplomatic skill, the see of Constantinople maintained its position against Rome during the so-called Photian Schism. When Pope Nicholas I (Nicholas I, Saint) challenged Photius' elevation to the patriarchate, deploring as uncanonical the six days' speed with which he had been advanced through the successive ranks of the hierarchy, the Byzantine patriarch refused to bow. He skillfully persuaded Nicholas' delegates to a council summoned at Constantinople to investigate the matter that he was the lawful patriarch despite the persisting claims of the rival Ignatian faction. Nicholas, alleging that his men had been bribed, excommunicated Photius; a council at Constantinople responded (867) by excommunicating Nicholas in turn. The immediate issues between the two sees were matters of ecclesiastical supremacy, the liturgy, and clerical discipline; behind these sources of division lay the question of jurisdiction over the converts in Bulgaria. And behind that question may be found centuries of growing separation between the minds and institutions of the eastern and the western Mediterranean worlds, symbolized in the roles assumed by two among the major protagonists in the Photian Schism. It was the supreme spiritual authority, the pope, who hurled anathemas from the West, but it was God's vicegerent on Earth, the emperor Michael III, who presided at the council of 867.

Michael did not long survive this moment of triumph. Later that year, he was murdered by his favourite, Basil (Basil I), who, on his bloody path to the throne, had earlier disposed of Caesar Bardas. As had Heraclius and Leo III before him, Basil came to found a dynasty, in this instance the Macedonian house. Unlike his predecessors, he came not as a saviour but as a peasant adventurer to seize an already sound empire whose next centuries were to be its greatest (see also Eastern Orthodoxy: History (Eastern Orthodoxy)).

Under the Macedonians, at least until the death of Basil II in 1025, the empire enjoyed a golden age. Its armies regained the initiative against the Arabs in the East, and its missionaries evangelized the Slavs (Slav), extending Byzantine influence in Russia and the Balkans. And, despite the rough military character of many of the emperors, there was a renaissance in Byzantine letters and important developments in law and administration. At the same time there were signs of decay: resources were squandered at an alarming rate; there was growing estrangement from the West; and a social revolution in Anatolia was to undermine the economic and military strength of the empire.

The empire was in theory an elective monarchy with no law of succession. But the desire to found and perpetuate a dynasty was strong, and it was often encouraged by popular sentiment. This was especially true in relation to the Macedonian dynasty, the founder, Basil I, having murdered his way to the throne in 867. Probably of Armenian descent, though they had settled in Macedonia, Basil's family was far from distinguished and can hardly have expected to produce a line of emperors that lasted through six generations and 189 years. But, having acquired the imperial crown, Basil tried to make sure that his family would not lose it and nominated three of his sons as coemperors. Though he was his least favourite, through the scholarly Leo VI, who succeeded him in 886, the succession was at least secure. Even the three soldier-emperors who usurped the throne during the Macedonian era were conscious, in varying degrees, that they were protecting the rights of a legitimate heir during a minority: Romanus I Lecapenus for Constantine VII, the son of Leo VI; and Nicephorus Phocas and John Tzimisces for Basil II, the grandson of Constantine VII.

A reassertion of Byzantine military and naval power in the East began with victories over the Arabs by Michael III's general Petronas in 856. From 863 the initiative lay with the Byzantines. The struggle with the Arabs, which had long been a struggle for survival, became a mounting offensive that reached its brilliant climax in the 10th century. By 867 a well-defined boundary existed between the Byzantine Empire and the territory of the ʿAbbāsid (Abbāsid Dynastyʿ) caliphate. Its weakest point was in the Taurus Mountains above Syria and Antioch. Basil I directed his operations against this point, recovered Cyprus for a while, and campaigned against the Paulicians, a heretical Christian sect whose anti-imperial propaganda was effective in Anatolia. But the conflict with Islam was one that concerned the whole empire, in the West as well as in the East, and by sea as well as by land. In 902 the Arabs completed the conquest of Sicily, but they were kept out of the Byzantine province of South Italy, for whose defense Basil I had even made some effort to cooperate with the Western emperor Louis II. The worst damage, however, was done by Arab pirates who had taken over the island of Crete. In 904 they plundered Thessalonica, carrying off quantities of loot and prisoners. Leo VI sent a naval expedition to Crete in 911, but the Muslims drove it off and humiliated the Byzantine navy off Chios in 912.

On the eastern frontier, the Byzantine offensive was sustained with great success during the reign of Romanus I Lecapenus by an Armenian general John Curcuas (Gurgen), who captured Melitene (934) and then Edessa (943), advancing across the Euphrates into the caliph's territory. It was Curcuas who paved the way for the campaigns of the two soldier-emperors of the next generation. In 961 Nicephorus Phocas (Nicephorus II Phocas), then domestic (commander) of the armies in the West, reconquered Crete and destroyed the Arab fleet that had terrorized the Aegean for 150 years; he thereby restored Byzantine naval supremacy in the eastern Mediterranean. In 962 his strategy achieved unexpected triumphs all along the eastern frontier and culminated in the capture of Aleppo in Syria. When he was proclaimed emperor in March 963, Nicephorus appointed another Armenian general, John Tzimisces (John I Tzimisces), as domestic of the East, though he retained personal command of operations against the Arabs. By 965 he had driven them out of Cyprus and was poised for the reconquest of Syria. The revived morale and confidence of Byzantium in the East showed itself in the crusading zeal of Nicephorus Phocas and John Tzimisces for the reconquest of Syria and the Holy Land. The ground lost to Islam in the 7th century was thus fast being regained; and, although Jerusalem was never reached, the important Christian city of Antioch, seat of one of the patriarchs, was recaptured in 969. These victories were achieved largely by the new cavalry force built up by Nicephorus Phocas. In the areas recovered from the Arabs, land was distributed in military holdings with the interests of the cavalry in mind. But the victories were achieved at the expense of the western provinces, and an attempt to recover Sicily ended in failure in 965.

Although imperial territory in the East could be reclaimed only by military conquest, in the Balkans and in Greece the work of reclamation could be assisted by the diplomatic weapon of evangelization. The Slavs (Slav) and the Bulgars could be brought within the Byzantine orbit by conversion to Christianity. The conversion of the Slavs was instigated by the patriarch Photius and carried out by the monks Cyril and Methodius from Thessalonica. Their invention of the Slavonic alphabet (Cyrillic (Cyrillic alphabet) and Glagolitic) made possible the translation of the Bible and the Greek liturgy and brought literacy as well as the Christian faith to the Slavic peoples. The work began in the Slavic Kingdom of Moravia and spread to Serbia and Bulgaria. Latin missionaries resented what they considered to be Byzantine interference among the northern Slavs, and there were repeated clashes of interest that further damaged relations between the sees of Rome and Constantinople. The conversion of the Bulgars became a competition between the two churches and was ably exploited by the Bulgar king Boris (Boris I) until, in 870, he opted for Orthodox Christianity on condition of having an archbishop of his own.

The trade with Constantinople that followed the missionaries whetted the appetites of the Slavs and Bulgars for a larger share in the material wealth of Byzantium. Simeon (Simeon I) (Symeon) I of Bulgaria, who succeeded his father Boris in 893 and who had been educated at Constantinople, proved to be an even more dangerous enemy than the Arabs. His efforts to become emperor dominated Byzantine history for some 15 years. In 913 he brought his army to the walls of Constantinople, demanding the imperial title. The patriarch, Nicholas Mysticus, appeased Simeon for a time, but it was Romanus Lecapenus who, by patience and diplomacy, undermined the power of the Bulgars and thwarted Simeon's ambitions. Simeon died in 927, and his son Peter I came to terms with Byzantium and married a granddaughter of Romanus.

The Russians lay far outside the Roman jurisdiction. Their warships, sailing down the Dnepr from Kiev to the Black Sea, first attacked Constantinople in 860. They were beaten off, and almost at once Byzantine missionaries were sent into Russia. The Russians were granted trading rights in Constantinople in 911, but in 941 and 944, led by Prince Igor, they returned to the attack. Both assaults were repelled, and Romanus I (Romanus I Lecapenus) set about breaking down the hostility and isolationism of the Russians by diplomatic and commercial contacts. In 957 Igor's widow, Olga (Olga, Saint), was baptized and paid a state visit to Constantinople during the reign of Constantine VII; her influence enabled Byzantine missionaries to work with greater security in Russia, thus spreading Christianity and Byzantine culture. Olga's son Svyatoslav (Svyatoslav I) was pleased to serve the empire as an ally against the Bulgars from 968 to 969, though his ambition to occupy Bulgaria led to war with Byzantium in which he was defeated and killed. In 971 John Tzimisces (John I Tzimisces) accomplished the double feat of humiliating the Russians and reducing Bulgaria to the status of a client kingdom. Byzantine influence over Russia reached its climax when Vladimir (Vladimir I) of Kiev, who had helped Basil II to gain his throne, received as his reward the hand of the Emperor's sister in marriage and was baptized in 989. The mass conversion of the Russian people followed, with the establishment of an official Russian Church subordinate to the patriarch of Constantinople.

The Bulgars, however, were not content to be vassals of Byzantium and rebelled under Samuel, youngest of the four sons of a provincial governor in Macedonia. Samuel made his capital at Ochrida and created a Bulgarian empire stretching from the Adriatic to the Black Sea and even, for a while, into Greece, though Thessalonica remained Byzantine. The final settlement of the Bulgar problem was worked out by Basil II in a ruthless and methodical military campaign lasting for some 20 years, until, by 1018, the last resistance was crushed. Samuel's dominions became an integral part of the Byzantine Empire and were divided into three new themes. At the same time the Slav principalities of Serbia (Rascia and Dioclea) and Croatia became vassal states of Byzantium, and the Adriatic port of Dyrrhachium came under Byzantine control. Not since the days of Justinian had the empire covered so much European territory. But the annexation of Bulgaria meant that the Danube was now the only line of defense against the more northerly tribes, such as the Pechenegs, Cumans, and Magyars.

The extension of Byzantine interests to the Adriatic, furthermore, had raised again the question of Byzantine claims to South Italy and, indeed, to the whole western part of the old Roman Empire. The physical separation of that empire into East and West had been emphasized by the settlement of the Slavs in the Balkan Peninsula and in Greece, and since the 7th century the two worlds had developed in their different ways. Their differences had been manifested in ecclesiastical conflicts, such as the Photian Schism. The conversion of the Slavs had produced bitterness between the agents of the rival jurisdictions. But the reestablishment of Byzantine authority in Greece and eastern Europe, added to the gains against the Muslim powers in Asia, reinforced the Byzantine belief in the universality of the empire, to which Italy and the West must surely be reunited in time. Until that time came, the fiction was maintained that the rulers of western Europe, like those of the Slavs, held their authority by virtue of their special relationship with the one true emperor in Constantinople.

It was sometimes suggested that a marriage alliance might bring together the Eastern and Western parts of the empire and so provide for a united defense against the common enemy in Sicily—the Arabs. In 944 Romanus II, son of Constantine VII, married a daughter of Hugh of Provence, the Carolingian claimant to Italy. Constantine VII also kept up diplomatic contact with Otto I, the Saxon king of Germany. But the case was dramatically altered when Otto was crowned emperor of the Romans (Holy Roman Empire) in 962, for this was a direct affront to the unique position of the Byzantine emperor. Otto tried, and failed, to establish his claim, either by force in the Byzantine province in Italy or by negotiation in Constantinople. His ambassador Liudprand of Cremona wrote an account of his mission to Nicephorus Phocas in 968 and of the Emperor's scornful rejection of a proposed marriage between Otto's son and a Byzantine princess. The incident vividly demonstrates the superior attitude of the Byzantines toward the West in the 10th century. John Tzimisces relented to the extent of arranging for one of his own relatives to marry Otto II in 972, though the arrangement implied no recognition of a Western claim to the empire. Basil II agreed that Otto III also should marry a Byzantine princess. But this union was never achieved; and subsequently Basil reorganized the administration of Byzantine Italy and was preparing another campaign against the Arabs in Sicily at the time of his death in 1025. The myth of the universal Roman Empire died hard.

The Iconoclastic Controversy had aggravated the estrangement of the Byzantine Church and Empire from the West. But it helped to define the tenets of Orthodoxy; and it had an effect on the character of Byzantine society for the future. On the one hand, the church acquired a new unity and vitality: its missionaries spread the Orthodox faith in new quarters of the world, its monasteries proliferated, and its spiritual tradition was carried forward by the sermons and writings of the patriarch Photius in the 9th century and of Symeon the New Theologian in the 10th and 11th centuries. On the other hand, the empire became more aware of its Greco-Roman heritage. Interest in classical Greek scholarship revived following the reorganization of the University of Constantinople under Michael III. The revival was fostered and patronized particularly by the scholar-emperor Constantine VII Porphyrogenitus, who saw to the compilation of three great works on the administration, the court ceremonies, and the provinces of his empire. He also commissioned a history of the age to which he contributed a biography of his grandfather Basil I. The age produced little original research, but lexicons (such as the 10th-century Suda), anthologies, encyclopaedias, and commentaries (such as the Lexicon and Bibliotheca of Photius) were produced in great number. The soldier-emperors of the 10th century were less interested in intellectual pursuits, but scholarship received a new impetus in the 11th century with Michael Psellus.

The founder of the dynasty, Basil I, and his son Leo VI, made plain their intention to inaugurate a new era by a restatement of the imperial law. Basil hoped to make a complete revision of the legal code, but only a preliminary textbook (Procheiron) with an introduction (Epanagoge) appeared during his reign. Leo VI, however, accomplished the work with the publication of the 60 books of the Basilica, which Hellenized the legal code of Justinian and made it more intelligible and accessible to lawyers. Additions and corrections to meet the needs of the time were incorporated in Leo's 113 novels (decrees), which represent the last substantial reform of the civil law in Byzantium. Enshrined in this legislation was the principle of the absolute autocracy of the emperor as being himself the law. The Senate, the last vestige of Roman republican institutions, was abolished. Only in the matter of the spiritual welfare of his subjects did the emperor recognize any limits to his authority. The ideal relationship of a dyarchy between emperor and patriarch, the body and the soul of the empire, was written into the Epanagoge of Basil I, in a section probably composed by Photius.

The administration in this period was ever more closely centralized in Constantinople, with an increasingly complex and numerous bureaucracy of officials who received their appointments and their salaries from the emperor. The emperor also controlled the elaborate machinery of the foreign and diplomatic service. Some of his civil servants, however, were powerful enough to play the part of kingmakers, notably Basil, the chamberlain who engineered the ascent to the throne of Nicephorus Phocas and John Tzimisces. Order and the regulation of trade, commerce, and industry in the capital were in the hands of the prefect of the city, whose functions are outlined in the 9th-century Book of the Eparch. He was responsible for organizing and controlling the guilds or colleges of craftsmen and retailers, whose legal rights and duties to the state were strictly circumscribed and supervised. The provinces in Europe and Asia were administered according to their territorial division into themes (theme), which, by the 10th century, numbered more than 30. The themes, though subdivided and reduced in size, retained their military character. Their governors, or stratēgoi (strategus), combined military and civil authority and were directly answerable to the emperor, who appointed them. The army and the navy were, for the most part, recruited from the ranks of soldier-farmers who held hereditary grants of land within the territory of each theme. The border districts were protected by contingents of frontier troops, led by their own officers or lords of the marches. Their exploits and adventures were romanticized in the 10th-century folk-epic of Digenis Akritas. But warfare was studied and perfected as a science, and it was the subject of treatises such as the Tactica of Leo VI, derived from the Strategicon of the emperor Maurice.

The wars of reconquest on the eastern frontier in this period and the general military orientation of imperial policy brought to the fore a new class of aristocracy, whose wealth and power were based on land ownership and who held most of the higher military posts. Trade and industry in the cities were so rigidly controlled by the government that almost the only profitable form of investment for private enterprise was the acquisition of landed property. The military aristocracy, therefore, took to buying up the farms of free peasants and soldiers and reducing their owners to varying forms of dependence. As the empire grew stronger, the rich became richer. Given the system of agriculture prevailing in Anatolia and the Balkans, every failure of crops, every famine, drought, or plague produced a quota of destitute peasant-soldiers willing to turn themselves and their land over to the protection of a prosperous and ambitious landlord. The first emperor to see the danger in this development was Romanus I Lecapenus, who, in 922 and 934, passed laws to defend the small landowners against the acquisitive instincts of the “powerful”; for he realized that the economic as well as the military strength of the empire depended on the maintenance within the theme system of the institution of free, yet tax-paying, soldier-farmers and peasants in village communities. (Only freemen owed military service.)

Successive emperors after Romanus I enforced and extended his agrarian legislation. But the cost of the campaigns of reconquest from the Arabs had to be met by higher taxation, which drove many of the poorer peasants to sell their lands and to seek security as tenant farmers. Nicephorus Phocas (Nicephorus II Phocas), who belonged to one of the aristocratic landowning families of Anatolia, was naturally reluctant to act against members of his own class, though he adhered to the principle that the rights of the poor should be safeguarded. His laws about land tenure were particularly directed toward the creation of a more mobile force of heavy-armed cavalry recruited from those who could afford the equipment, which inevitably brought changes in the social structure of the peasant militia. On the other hand, Nicephorus took a firm line to prevent the accumulation of further land by the church, and he forbade any addition to the number of monasteries, whose estates, already extensive, were unproductive to the economy.

The last emperor to attempt to deal with the problem of land ownership seriously was Basil II, whose rise to the throne had involved the empire in a bitter and costly war against the aristocratic Sclerus and Phocas families. In 996 Basil promulgated comprehensive punitive legislation against the landed families, ordering the restitution of land acquired from the peasantry since 922 and requiring proof of title to other land going back in some cases as far as 1,000 years. Further, the system of collective responsibility for the payment of outstanding taxes known as the allelengyon now devolved not on the rest of the village community but on the nearest large landowner, whether lay or ecclesiastical. Basil's conquest of Bulgaria somewhat altered the social and economic pattern of the empire, for new themes were created there in which there was no long tradition of a landed aristocracy as in Anatolia. After his death in 1025 the powerful hit back, and the government in Constantinople was no longer able to check the absorption of small freeholders by the great landowners and the consequent feudalization of the empire.

This process was particularly disastrous for the military establishment. The success and prestige of the Byzantine Empire in the Macedonian era to a large extent depended on the unrivaled efficiency of its army in Anatolia. A professional force, yet mainly native to the soil and so directly concerned with the defense of that soil, it had no equal in the Western or the Arab world at the time. And yet it was in this institution that the seeds of decay and disintegration took root; for most of the army's commanders were drawn from the great landowners of Anatolia, who had acquired their riches and their status by undermining the social and economic structure on which its recruitment depended. Basil II had restrained them with such an iron hand that a reaction was inevitable after his death. Indeed, it is doubtful if Byzantine society could have tolerated another Basil II, despite all his triumphs. Soured by long years of civil war at the start of his reign, ascetic and uncultured by nature, Basil embodied the least attractive features of Byzantine autocracy. Some have called him the greatest of all the emperors. But the virtue of philanthropy, which the Byzantines prized and commended in their rulers, was not a part of his greatness; and the qualities that lent refinement to the Byzantine character, among them a love of learning and the arts, were not fostered during his reign. Yet, while Basil was busily earning his title of Bulgaroctonus (“Bulgar Slayer”), St. Symeon the New Theologian was exploring the love of God for man in some of the most poetic homilies in all mystical literature.

Basil II never married. But after his death his relatives remained in possession of the throne until 1056, less because of their efficiency than because of a general feeling among the Byzantine people that the prosperity of the empire was connected with the continuity of the Macedonian dynasty. When Basil's brother Constantine VIII died in 1028, the line was continued in his two daughters, Zoe and Theodora. Zoe was married three times: to Romanus III Argyrus (ruled 1028–34), to Michael IV (1034–41), and to Constantine IX Monomachus (1042–55), who outlived her. When Constantine IX died in 1055, Zoe's sister, Theodora, reigned alone as empress until her death a year later.

The great emperors of the golden age, not all of them members of the Macedonian family, molded the history of that age. The successors of Basil II were rather the creatures of circumstances, because they did not make and seldom molded. In the 56 years from 1025 to 1081, there were 13 emperors. An attempt made by Constantine X Ducas to found a new dynasty was disastrously unsuccessful. Not until the rise of Alexius I Comnenus to power, in 1081, was stability restored by an ensured succession in the Comnenus family, who ruled for more than 100 years (1081–1185).

The state of the Byzantine Empire in the 11th century may be compared to that of the Roman Empire in the 3rd century, when, after a long period of secure prosperity, new pressures from beyond the frontiers aggravated the latent tensions in society. The brief reigns of Basil II's heirs reflected, and were often the product of, a division in the Byzantine ruling class, a conflict between the military aristocracy of the provinces and the civilian aristocracy, or bureaucracy, of Constantinople. Each faction put up rival emperors. The sophisticated urban aristocracy favoured rulers who would reverse the militaristic trend of the empire and who would expand the civil service and supply them and their families with lucrative offices and decorative titles. The military families, whose wealth lay not in the capital but in the provinces and who had been penalized by Basil II's legislation, favoured emperors who were soldiers and not civil servants. In this they were more realistic, for in the latter part of the 11th century it became ever clearer that the empire's military strength was no longer sufficient to hold back its enemies. The landowners in the provinces appreciated the dangers more readily than the government in Constantinople, and they made those dangers an excuse to enlarge their estates in defiance of all the laws passed in the 10th century. The theme system in Anatolia, which had been the basis of the empire's defensive and offensive power, was rapidly breaking down at the very moment when its new enemies were gathering their strength.

On the other hand, the urban aristocracy of Constantinople, reacting against the brutalization of war, strove to make the city a centre of culture and sophistication. The university was endowed with a new charter by Constantine IX in 1045, partly to ensure a steady flow of educated civil servants for the bureaucracy. The law school was revived under the jurist John Xiphilinus; the school of philosophy was chaired by Michael Psellus (Psellus, Michael), whose researches into every field of knowledge earned him a reputation for omniscience and a great following of brilliant pupils. Psellus—courtier, statesman, philosopher, and historian—is in himself an advertisement for the liveliness of Byzantine society in the 11th century. What he and others like him failed to take into account was that their empire was more and more expending the resources and living on the reputation built up by the Macedonian emperors.

The new enemies that emerged in the 11th century, unlike the Arabs or the Bulgars, had no cause to respect that reputation. They appeared almost simultaneously on the northern, the eastern, and the western frontiers. It was nothing new for the Byzantines to have to fight on two fronts at once. But the task required a soldier on the throne. The Pechenegs, a Turkic tribe, had long been known as the northern neighbours of the Bulgars. Constantine VII had thought them to be valuable allies against the Bulgars, Magyars, and Russians. But after the conquest of Bulgaria, the Pechenegs began to raid across the Danube into what was then Byzantine territory. Constantine IX allowed them to settle south of the river, where their numbers and their ambitions increased. By the mid-11th century they were a constant menace to the peace in Thrace and Macedonia, and they encouraged the spirit of revolt among the Bogomil heretics in Bulgaria. It was left to Alexius I to avert a crisis by defeating the Pechenegs in battle in 1091.

The new arrivals on the eastern frontier were the Seljuq Turks, whose conquests were to change the whole shape of the Muslim and Byzantine worlds. In 1055, having conquered Persia, they entered Baghdad, and their prince assumed the title of sultan and protector of the ʿAbbāsid caliphate. Before long they asserted their authority to the borders of Fāṭimid Egypt and Byzantine Anatolia. They made their first explorations across the Byzantine frontier into Armenia in 1065 and, in 1067, as far west as Caesarea in central Anatolia. The raiders were inspired by the Muslim idea of holy war, and there was at first nothing systematic about their invasion. They found it surprisingly easy, however, to plunder the countryside and isolate the cities, owing to the long neglect of the eastern frontier defenses by the emperors in Constantinople. The emergency lent weight to the military aristocracy in Anatolia who, in 1068, finally secured the election of one of their own number, Romanus IV Diogenes, as emperor. Romanus assembled an army to deal with what he saw as a large-scale military operation. It was a sign of the times that his army was mainly composed of foreign mercenaries. In August 1071 it was defeated at Manzikert (Manzikert, Battle of), near Lake Van in Armenia. Romanus was taken prisoner by the Seljuq sultan, Alp-Arslan. He was allowed to buy his freedom after signing a treaty, but the opposition in Constantinople refused to have him back as emperor and installed their own candidate, Michael VII (Michael VII Ducas). Romanus was treacherously blinded. The Seljuqs were thus justified in continuing their raids and were even encouraged to do so. Michael VII invited Alp-Arslan to help him against his rivals, Nicephorus Bryennius and Nicephorus Botaneiates (Nicephorus III Botaneiates), each of whom proclaimed himself emperor at Adrianople in 1077 and at Nicaea in 1078. In the four years of ensuing civil war there were no troops to defend the eastern frontier. By 1081 the Turks had reached Nicaea. The heart of the empire's military and economic strength, which the Arabs had never mastered, was now under Turkish rule.

The new enemies in the West were the Normans (Norman), who began their conquest of South Italy early in the 11th century. Basil II's project of recovering Sicily from the Arabs had been almost realized in 1042 by the one great general of the post-Macedonian era, George Maniaces, who was recalled by Constantine IX and killed as a pretender to the throne. The Normans thereafter made steady progress in Italy. Led by Robert Guiscard (Robert), they carried all before them; in April 1071, Bari, the last remaining Byzantine stronghold, fell after a three-year siege. Byzantine rule in Italy and the hope of a reconquest of Sicily were at an end.

The disasters at Manzikert and at Bari, in the same year 1071, at opposite extremes of the empire, graphically illustrate the decline of Byzantine power. The final loss of Italy seemed to underline the fact of the permanent division between the Greek East and the Latin West, which was now not only geographical and political but also increasingly cultural and ecclesiastical. In 1054 a state of schism had been declared between the churches of Rome and Constantinople. The political context of the event was the Norman invasion of Italy, which at the time was a matter of as much concern to the papacy as it was to Byzantium. But the event itself, the excommunication of the patriarch Michael Cerularius by Cardinal Humbert (Humbert of Silva Candida) in Constantinople, symbolized an irreconcilable difference in ideology. The reform movement in the Roman Church had emphasized an ideal of the universal role of the papacy that was wholly incompatible with Byzantine tradition. Both sides also deliberately aggravated their differences by reviving all the disputed points of theology and ritual that had become battle cries during the Photian Schism in the 9th century. The schism of 1054 (1054, Schism of) passed unnoticed by contemporary Byzantine historians; its significance as a turning point in East–West relations was fully realized only later.

The Venetians had been pleased to help drive the Normans out of the Adriatic Sea but demanded a heavy price. In 1082 Alexius granted them trading privileges in Constantinople and elsewhere on terms calculated to outbid Byzantine merchants. This charter was the cornerstone of the commercial empire of Venice in the eastern Mediterranean. But it fed the flames of Byzantine resentment against the Latins, and it provoked the rich, who might have been encouraged to invest their capital in shipbuilding and trade, to rely on the more familiar security of landed property.

The terms that Alexius made with his enemies in the first 10 years of his reign were not meant to be permanent. He fully expected to win back Anatolia from the Seljuqs; his plans, however, were not given time to mature, for matters were precipitated by the arrival in the East of the first Crusaders from western Europe (1096). Alexius had undoubtedly solicited the help of mercenary troops from the West but not for the liberation of the Holy Land from the infidels. The urgent need was the protection of Constantinople and the recovery of Anatolia. The Byzantines were more realistic about their Muslim neighbours than the distant popes and princes of the West. Jerusalem had finally been taken by the Seljuqs in 1071, but the most immediate threat to Byzantium came from the Pechenegs and the Normans. Alexius was tactful in his dealings with the pope and ready to discuss the differences between the churches. But neither party foresaw the consequences of Pope Urban II's appeal in 1095 for recruits to fight a Holy War (Crusades). The response in western Europe was overwhelming. The motives of those who took the cross as Crusaders ranged from religious enthusiasm to a mere spirit of adventure or a hope of gain, and it was no comfort to Alexius to learn that four of the eight leaders of the First Crusade were Normans—among them Bohemond (Bohemond I), the son of Robert Guiscard. Since the Crusade had to pass through Constantinople, however, the Emperor had some control over it. He required its leaders to swear to restore to the empire any towns or territories they might conquer from the Turks on their way to the Holy Land. In return he gave them guides and a military escort. Still, the cost was enormous, for the Crusaders had to be supplied with food or live off the land as they went.

Nicaea fell to them in 1097 and was duly handed over to the Emperor in accord with the agreement. In 1098 they reached and captured Antioch. There the trouble started. Bohemond refused to turn over the city and instead set up his own principality of Antioch. His example was imitated in the establishment of the Latin kingdom of Jerusalem (Jerusalem, kingdom of) (1100), which had fallen to the Crusaders the year before, and of the counties of Edessa and Tripoli. The Crusaders settled down to colonize and defend the coast of Palestine and Syria and to quarrel among themselves. While they did so, Alexius was able to establish a new and more secure boundary between Byzantium and Islām through the middle of Anatolia. Full advantage was taken of the prevailing rivalry between the Seljuq sultans at Konya and the rival dynasty of the Dānishmend emirs at Melitene (near modern Malatya, Turkey), and a limit was set to the westward expansion of the Turks.

The First Crusade thus brought some benefits to Byzantium. But nothing could reconcile the emperor to Bohemond of Antioch. In 1107 Bohemond mounted a new invasion of the empire from Italy. Alexius was ready and defeated him at Dyrrhachium in 1108. Byzantine prestige was higher than it had been for many years, but the empire could barely afford to sustain the cost of being a great power. Alexius reconstituted the army and re-created the fleet, but only by means of stabilizing the gold coinage at one-third of its original value and by imposing a number of supplementary taxes. It became normal practice for taxes to be farmed out, which meant that the collectors recouped their outlay on their own terms. People in the provinces had the added burden of providing materials and labour for defense, communications, and provisions for the army, which now included very large numbers of foreigners. The supply of native soldiers had virtually ceased with the disappearance or absorption of their military holdings. Alexius promoted an alternative source of native manpower by extending the system of granting estates in pronoia (pronoia system) (by favour of the emperor) and tying the grant to the military obligation. The recipient of a pronoia was entitled to all the revenues of his estate and to the taxes payable by his tenants (paroikoi), on condition of equipping himself as a mounted cavalryman with a varying number of troops. He was in absolute possession of his property until it reverted to the crown upon his death. Similarly, Alexius tried to promote more profitable development of the estates of the church by granting them to the management of laymen as charistikia, or benefices. As an expedient, the pronoia system had advantages both for the state and for the military aristocracy who were its main beneficiaries. But in the long term it hastened the fragmentation of the empire among the landed families and the breakdown of centralized government that the 10th-century emperors had laboured to avert.

No such cooperation was possible with Conrad's successor, Frederick I Barbarossa (after 1152). To Frederick the alliance between the Holy Roman Empire and what he called “the kingdom of the Greeks” was not one between equals. Manuel launched a vain invasion of the Norman kingdom on his own account in 1154, but it was too late for a revival of Byzantine imperialism in the West. It was hard for the Byzantines to accept the fact that their empire might soon become simply one among a number of Christian (Christianity) principalities.

In the Balkans and in the Latin East Manuel was more successful. His armies won back much of the northwest Balkans and almost conquered Hungary, reducing it to a client kingdom of Byzantium. The Serbs, too, under their leader Stefan Nemanja, were kept under control, while Manuel's dramatic recovery of Antioch in 1159 caused the Crusaders to treat the Emperor with a new respect. But in Anatolia he overreached himself. To forestall the formation of a single Turkish sultanate, Manuel invaded the Seljuq territory of Rūm in 1176. His army was surrounded and annihilated at Myriocephalon. The battle marked the end of the Byzantine counteroffensive against the Turks begun by Alexius I. Its outcome delighted the Western emperor, Frederick I Barbarossa, who had supported the Seljuq sultan of Rūm against Manuel and who now openly threatened to take over the Byzantine Empire by force.

Manuel's personal relationships with the Crusaders and with other Westerners remained cordial to the end. But his policies had antagonized the Holy Roman Empire, the papacy, the Normans, and, not least, the Venetians. His effort to revive Byzantine prestige in Italy and the Balkans and his treaties with Genoa (1169) and Pisa (1170) roused the suspicions of Venice, and in 1171, following an anti-Latin demonstration in Constantinople, all Venetians in the empire were arrested and their property was confiscated. The Venetians did not forget this episode. They, too, began to think in terms of putting Constantinople under Western control as the only means of securing their interest in Byzantine trade.

Manuel's policies antagonized many of his own people as well. His favouritism to the Latins was unpopular, as was his lavish granting of estates in pronoia. A reaction set in shortly after his death in 1180, originated by his cousin Andronicus I Comnenus, who ascended to the throne after another anti-Latin riot in Constantinople. Andronicus murdered Manuel's widow and son Alexius II. He posed as the champion of Byzantine patriotism and of the oppressed peasantry. But to enforce his reforms he behaved like a tyrant. By undermining the power of the aristocracy he weakened the empire's defenses and undid much of Manuel's work. The King of Hungary broke his treaty, and Stephen Nemanja of Serbia declared his independence from Byzantium and founded a new Serbian kingdom. Within the empire, too, disintegration proceeded. In 1185 Isaac Comnenus (Isaac I Comnenus), governor of Cyprus, set himself up as independent ruler of the island. In the same year the Normans again invaded Greece and captured Thessalonica. The news prompted a counterrevolution in Constantinople, and Andronicus was murdered.

He was the last of the Comnenian family to wear the crown. His successor, Isaac II Angelus, was brought to power by the aristocracy. His reign, and, still more, that of his brother Alexius III (Alexius III Angelus), saw the collapse of what remained of the centralized machinery of Byzantine government and defense. Isaac tried at least to keep his foreign enemies in check. The Normans were driven out of Greece in 1185. But in 1186 the Bulgars began a rebellion that was to lead to the formation of the Second Bulgarian Empire. Matters were not made easier by the arrival of the Third Crusade (Crusades), provoked by the loss of Jerusalem to the Muslim leader Saladin in 1187. One of its leaders was Frederick I Barbarossa, whose avowed intention was to conquer Constantinople. He died on his way to Syria. But Richard I the Lion-Heart of England appropriated Cyprus from Isaac Comnenus, and the island never again reverted to Byzantine rule.

In 1195 Isaac II was deposed and blinded by his brother Alexius III. The Westerners, who had again blamed the failure of their Crusade on the Byzantines, saw ways of exploiting the situation. The emperor Henry VI had united the Norman Kingdom of Sicily with the Holy Roman Empire. He inherited the ambitions of both to master Constantinople, and his brother, Philip of Swabia, was married to a daughter of the dethroned Isaac II. Alexius bought off the danger by paying tribute to Henry, but Henry died in 1197. The idea had now gained ground in the West that the conquest of Constantinople would solve a number of problems and would be of benefit not only to trade but also to the future of the Crusade and the church. In 1198 Innocent III was elected pope. The new rulers of Hungary, Serbia, and Bulgaria all turned to him for the recognition of the sovereignty that Byzantium would not give them.

It was under Innocent's inspiration that the Fourth Crusade (Crusades) was launched, and it was by the diversion of that Crusade from its purpose and objective that the conquest and colonization of the Byzantine Empire by the West was realized. A multiplicity of causes and coincidences led up to the event, but the ambition of Venice, which supplied the ships, must rank high among them. A plausible excuse was offered by the cause of restoring Isaac II, whose son Alexius IV (Alexius IV Angelus) had escaped to the West to seek help, and who made lavish promises of reward to his benefactors. But when, in 1203, the Crusaders drove Alexius III out of Constantinople, Isaac II and his son proved incapable either of fulfilling the promises or of stifling the anti-Latin prejudice of their people, who proclaimed an emperor of their own in the person of Alexius V (Alexius V Ducas Mourtzouphlus). The Venetians and Crusaders therefore felt justified in taking their own reward by conquering and dividing Constantinople and the Byzantine provinces among themselves. The city fell to them in April 1204. They worked off their resentment against the inhabitants in an unparalleled orgy of looting and destruction, which did irreparable damage to the city and immeasurable harm to East–West understanding.

The Venetians, led by their doge, Enrico Dandolo (Dandolo, Enrico), gained most from the enterprise by appropriating the principal harbours and islands on the trade routes. The Crusaders set about the conquest of the European and Asiatic provinces. The first Latin emperor, Baldwin I, was the suzerain of the feudal principalities that they established in Thrace, Thessalonica, Athens, and the Morea (Peloponnese). He soon came into conflict with the ruler of Bulgaria. Still more serious was the opposition offered by the three provincial centres of Byzantine resistance. At Trebizond (Trabzon) on the Black Sea, two brothers of the Comnenian family laid claim to the imperial title. In Epirus in northwestern Greece Michael Angelus Ducas, a relative of Alexius III, made his capital at Arta and harassed the Crusader states in Thessaly. The third centre of resistance was based on the city of Nicaea in Anatolia, where Theodore I Lascaris, another relative of Alexius III, was crowned as emperor in 1208 by a patriarch of his own making. Of the three, Nicaea lay nearest to Constantinople, between the Latin Empire and the Seljuq sultanate of Rūm; and its emperors proved worthy of the Byzantine traditions of fighting on two fronts at once and of skillful diplomacy. Theodore Lascaris and his son-in-law John III Vatatzes built up at Nicaea a microcosm of the Byzantine Empire and church in exile. The Latins were thus never able to gain a permanent foothold in Anatolia; and even in Europe their position was constantly threatened by the Byzantine rulers of northern Greece, though in the centre and south of the country their conquests were more lasting.

The most successful of the Latin emperors was Baldwin's brother, Henry (Henry of Hainault) of Flanders, after whose death in 1216 the Latin Empire lost the initiative and the recovery of Constantinople became a foreseeable goal for the Byzantines in exile. The Latin regime was prolonged less by its own vitality than by the inability of the successor states of Epirus and Nicaea to cooperate. In 1224 Theodore Ducas of Epirus, who had extended his territories across the north of Greece and far into Bulgaria, wrested Thessalonica from the Latins and was crowned emperor there in defiance of the Emperor in Nicaea. In 1230, however, he was defeated in battle against the Bulgars before reaching Constantinople; and his defeat gave John III Ducas Vatatzes the chance to extend his own empire into Europe, to ally with the Bulgars, and so to encircle Constantinople. Theodore's successor was made to renounce his imperial title, and Thessalonica surrendered to the empire of Nicaea in 1246. The Mongol invasion of Anatolia, which had meanwhile thrown the East into confusion, was of great benefit to Nicaea, for it weakened the Seljuq sultanate and isolated the rival empire of Trebizond.

John Vatatzes might well have crowned his achievements by taking Constantinople had he not died in 1254. When his son Theodore II Lascaris (1254–58) died in 1258, leaving an infant son, John IV, the regency and then the throne in Nicaea were taken over by Michael VIII Palaeologus (reigned 1259–82). Michael came from one of the aristocratic families of Nicaea whom Theodore II had mistrusted. But it was he who carried the work of the Lascarid emperors to its logical conclusion. The Byzantine state in Epirus had revived under Michael II Ducas, who set his sights on Thessalonica. Despite several efforts to reach a diplomatic settlement, the issue between the rival contenders had finally to be resolved in battle at Pelagonia in Macedonia in 1259. Michael II was supported by William of Villehardouin, the French prince of the Morea, and by Manfred, the Hohenstaufen king of Sicily. The victory went to the army of Nicaea. Two years later a general of that army entered Constantinople. The last of the Latin emperors, Baldwin II, fled to Italy; and the Venetians were dispossessed of their lucrative commercial centre. In August 1261 Michael VIII was crowned as emperor in Constantinople; the boy heir to the throne of Nicaea, John IV Lascaris, was blinded and imprisoned. In this way, the dynasty of Palaeologus (Palaeologus family), the last to reign in Constantinople, was inaugurated.

The empire in exile at Nicaea had become a manageable and almost self-sufficient unit, with a thriving economy based on agriculture and, latterly, on trade with the Seljuqs. It had no navy but the land frontiers in Anatolia, policed by well-paid troops, were stronger than they had been since the 12th century. By stretching the frontiers into Europe the empire had not dissipated its strength; for the possession of Thessalonica balanced that of Nicaea. When the seat of government was moved from Nicaea to Constantinople, that balance was upset, the economy was re-oriented, and the defense system in Anatolia began to break down. Constantinople was still the New Jerusalem for the Byzantines. To leave it in foreign hands was unthinkable. But after the dismemberment of the empire by the Fourth Crusade, the city was no longer the focal point of an integrated structure. It was more like an immense city-state in the midst of a number of more or less independent provinces. Much of Greece and the islands remained in French or Italian hands. The Byzantine rulers of Epirus and Thessaly, like the emperors in Trebizond, refused to recognize Michael VIII as emperor. His treatment of the Lascarid heir of Nicaea, for which the patriarch Arsenius excommunicated him, appalled many of his own subjects and provoked what was known as the Arsenite schism in the Byzantine Church. Many in Anatolia, loyal to the memory of the Lascarid emperors who had enriched and protected them, condemned Michael VIII as a usurper.

The new dynasty was thus founded in an atmosphere of dissension, but its founder was determined that it should succeed. He took measures for the rehabilitation, repopulation, and defense of Constantinople. He stimulated a revival of trade by granting privileges to Italian merchants. The Genoese, who had agreed to lend him ships for the recovery of the city from their Venetian rivals, were especially favoured; and soon they had built their own commercial colony at Galata opposite Constantinople, and cornered most of what had long been a Venetian monopoly. Inevitably, this led to a conflict between Genoa and Venice, of which the Byzantines were the main victims. Some territory was taken back from the Latins, notably in the Morea and the Greek islands. But little was added to the imperial revenue; and Michael VIII's campaigns there and against Epirus and Thessaly ate up the resources that had been accumulated by the emperors at Nicaea.

The dominating influence on Byzantine policy for most of Michael's reign was the threat of reconquest by the Western powers. Charles of Anjou (Charles I), the brother of the French king Louis IX, displaced Manfred of Sicily and inherited his title in 1266; he then organized a coalition of all parties interested in re-establishing the Latin empire, posing as the pope's champion to lead a Crusade against the schismatic Greeks. Michael VIII countered this threat by offering to submit the Church of Constantinople to the see of Rome, thereby inviting the pope's protection and removing the only moral pretext for a repetition of the Fourth Crusade. The offer to reunite the churches had been made as a diplomatic ploy to previous popes by previous emperors, but never in such compelling circumstances. Pope Gregory X (Gregory X, Blessed) accepted it at its face value, and at the second Council of Lyon in 1274 a Byzantine delegation professed obedience to the Holy See in the name of their emperor. Michael's policy, sincere or not, was violently opposed by most of his people, and he had to persecute and imprison large numbers of them in order to persuade the papacy that the union of the churches was being implemented. Later popes were not convinced by the pretense. In 1281 Charles I (Charles of Anjou) invaded the empire. His army was beaten back in Albania, but he at once prepared a new invasion by sea, supported by Venice, Serbia, Bulgaria, and the separatist rulers of northern Greece. His plans, however, were wrecked in 1282 by a rebellion in Sicily called the Sicilian Vespers and by the intervention of Peter III of Aragon, which the Byzantines encouraged. Michael VIII died at the end of the same year. He had saved his empire from its most persistent enemy, but he died condemned by his church and people as a heretic and a traitor.

Whatever sins he may have committed in the eyes of the Orthodox Church, it is true that Michael VIII, by concentrating on the danger from the West, neglected, if he did not betray, the eastern provinces where he had come to power. Frontier defense troops in Anatolia were withdrawn to Europe or neglected, and bands of Turkish raiders, driven westward by the upheaval of the Mongol invasion, began to penetrate into Byzantine territory. Like the Seljuqs in the 11th century, the new arrivals found little organized opposition. Some of the local Byzantines even collaborated with them out of their own antipathy to the Emperor in Constantinople. By about 1280 the Turks were plundering the fertile valleys of western Anatolia, cutting communications between the Greek cities, and their emirs were beginning to carve out small principalities. Michael VIII's network of diplomacy covered the Mongols of Iran and the Golden Horde in Russia, as well as the Mamlūks of Egypt. But diplomacy was ineffective against Muslim (Islāmic world) Ghazis (warriors inspired by the ideal of holy war); by the time the threat from Italy was removed in 1282, it was almost too late to save Byzantine Anatolia.

Nor was it possible to raise armies to fight in Europe and Asia simultaneously. The native recruitment fostered by the Comnenian emperors had fallen off since 1261. Estates held in pronoia had become hereditary possessions of their landlords, who ignored or were relieved of the obligation to render military service to the government. The knights of the Fourth Crusade had found many familiar elements of feudalism in the social structure of the Byzantine provinces. By the end of the 13th century the development had gone much further. The officers of the Byzantine army were still mostly drawn from the native aristocracy. But the troops were hired, and the cost of maintaining a large army in Europe, added to the lavish subsidies that Michael VIII paid to his friends and allies, crippled the economy.

Michael's son Andronicus II (reigned 1282–1328) unwisely attempted to economize by cutting down the size of the army and disbanding the navy. Unemployed Byzantine sailors sold their services to the new Turkish emirs, who were already raiding the Aegean islands. The Genoese became the suppliers and defenders of Constantinople by sea, which excited the jealousy of the Venetians to the pitch of war and led to the first of a series of naval battles off Constantinople in 1296. In reaction against his father's policy, Andronicus II pursued a line of almost total isolation from the papacy and the West. The union of Lyon was solemnly repudiated and Orthodoxy restored, to the deep satisfaction of most Byzantines. But there were still divisive conflicts in society. The Arsenite schism in the church was not healed until 1310; the rulers of Epirus and Thessaly remained defiant and kept contact with the successors of Charles I in Italy; and the people of Anatolia aired their grievances in rebellion. As the Turks encroached on their land, refugees in growing numbers fled to the coast or to Constantinople, bringing new problems for the government. In 1302 a band of Turkish warriors defeated the Byzantine army near Nicomedia in northwestern Anatolia. Its leader, Osman I, was the founder of the Osmanli, or Ottoman, people, who were soon to overrun the Byzantine Empire in Europe.

In 1303 Andronicus hired a professional army of mercenaries, the Grand Catalan Company. The Catalans made one successful counterattack against the Turks in Anatolia. But they were unruly and unpopular, and when their leader was murdered they turned against their employers. For some years they used the Gallipoli Peninsula as a base from which to ravage Thrace, inviting thousands of Turks to come over and help them. The Catalans finally moved west; in 1311 they conquered Athens from the French and established the Catalan Duchy of Athens and Thebes. The Turks whom they left behind were not ejected from Gallipoli until 1312. The cost of hiring the Catalans, and then of repairing the damage that they had done, had to be met by desperate measures. The face value of the Byzantine gold coin, the hyperpyron, was lowered when its gold content was reduced to a mere 50 percent; and the people had to bear still greater burdens of taxation—some payable in kind by farmers. Inflation and rising prices led to near famine in Constantinople, the population of which was swollen by vast numbers of refugees.

The revival of mystical speculation and the monastic life may have been in part a reaction against the contemporary revival of secular literature and learning. Scholarship of all kinds was patronized by Andronicus II. As in the 11th century, interest was mainly centred on a rediscovery of ancient Greek learning. The scholar Maximus Planudes (Planudes, Maximus) compiled a famous anthology and translated a number of Latin works into Greek, though knowledge of Latin was rare and most of the Byzantine scholars prided themselves on having in their Hellenic heritage an exclusive possession that set them apart from the Latins. A notable exception was Demetrius Cydones (Cydones, Demetrius) who, like Michael Psellus, managed affairs of state for a number of emperors for close to 50 years. Cydones translated the works of Thomas Aquinas into Greek; he was the forerunner of a minority of Byzantine intellectuals who joined the Roman Church and looked to the West to save their empire from ruin. More typical of his class was Theodore Metochites (Metochites, Theodore), the Grand Logothete, or chancellor, of Andronicus II, whose encyclopaedic learning rivaled that of Psellus. His pupil Nicephorus Gregoras (Gregoras, Nicephorus), in addition to his researches in philosophy, theology, mathematics, and astronomy, wrote a history of his age. The tradition of Byzantine historiography, maintained by George Acropolites, the historian of the Empire of Nicaea, was continued in the 14th century by George Pachymeres, by Gregoras, and finally by the emperor John VI Cantacuzenus, who wrote his memoirs after his abdication in 1354.

The histories they wrote tell more of politics and personalities than of the underlying social and economic tensions in their society that were to find expression in a series of civil wars. Trouble broke out in 1320 when Andronicus II, purely for family reasons, disinherited his grandson Andronicus III (Andronicus III Palaeologus). The cause of the young emperor was taken up by his friends, and there was periodic warfare from 1321 to 1328, when the older Andronicus had to yield the throne. It was in some ways a victory for the younger generation of the aristocracy, of whom the leading light was John Cantacuzenus (John VI Cantacuzenus). It was he who guided the empire's policies during the reign of Andronicus III (1328–41). They were men of greater drive and determination, but the years of fighting had made recovery still more difficult and had given new chances to their enemies. In 1329 they fought and lost a battle at Pelekanon (near Nicomedia) against Osman's son, Orhan, whose Turkish warriors went on to capture Nicaea in 1331 and Nicomedia in 1337. Northwestern Anatolia, once the heart of the empire, was now lost. There seemed no alternative but to accept the fact and to come to terms with the Ottomans and the other Turkish emirs. By so doing, Andronicus III and Cantacuzenus were able to call on the services of almost limitless numbers of Turkish soldiers to fight for them against their other enemies: the Italians in the Aegean islands and the Serbs and the Bulgars in Macedonia and Thrace.

The power of Serbia, which Andronicus II had managed to control by diplomatic means, grew alarmingly after the accession of Stefan Dušan to the Serbian throne in 1331. Dušan exploited to the full the numerous embarrassments of the Byzantines and in 1346 announced his ambitions by having himself crowned as emperor of the Serbs and Greeks. The greatest practical achievement of Andronicus III was the restoration to Byzantine rule of the long-separated provinces of Epirus and Thessaly. But only a few years later, in 1348, the whole of northern Greece was swallowed up in the Serbian Empire of Stefan Dušan.

When Andronicus III died in 1341, civil war broke out for a second time. The contestants on that occasion were John Cantacuzenus, who had expected to act as regent for the boy-heir John V (John V Palaeologus), and his political rivals led by his former partisan Alexius Apocaucus, the patriarch John Calecas, and the empress mother Anne of Savoy, who held power in Constantinople. Cantacuzenus, befriended and then rejected by Dušan of Serbia, was crowned as Emperor John VI in Thrace in 1346; and, with the help of Turkish troops, he fought his way to victory in the following year. Like Romanus Lecapenus, he protested that he was no more than the protector of the legitimate heir to the throne, John V Palaeologus. His brief reign, from 1347 to 1354, might have turned the tide of Byzantine misfortunes had not the second civil war provoked unprecedented social and political consequences. In the cities of Thrace and Macedonia the people vented their dissatisfaction with the ruling aristocracy by revolution. It was directed mainly against Cantacuzenus and the class that he represented. The movement was most memorable and lasting in Thessalonica, where a faction known as the Zealots seized power in a coup d'état and governed the city as an almost independent commune until 1350.

The second civil war was consequently even more destructive of property and ruinous to the economy than the first. At the same time, in 1347, the Black Death decimated the population of Constantinople and other parts of the empire. John VI Cantacuzenus, nevertheless, did what he could to restore the economy and stability of the empire. To coordinate the scattered fragments of its territory he assigned them as appanages to individual members of the imperial family. His son Manuel took over the province of the Morea in 1349 with the rank of despot and governed it with growing success until his death in 1380; his eldest son, Matthew, was given a principality in Thrace; while the junior emperor John V, who had married a daughter of Cantacuzenus, ruled in Thessalonica after 1351.

Cantacuzenus also tried but failed to weaken the economic stranglehold of the Genoese by rebuilding a Byzantine war fleet and merchant navy. The effort involved him in warfare, first on his own and then as an unwilling partner of the Venetians against the Genoese, from which Byzantium emerged as the loser. The revenue of the Genoese colony at Galata, derived from custom dues, was now far greater than that of Constantinople. The empire's poverty was reflected in dilapidated buildings and falling standards of luxury. The crown jewels had been pawned to Venice during the civil war, and the Byzantine gold coin, hopelessly devalued, had given place in international trade to the Venetian ducat. More and more, Byzantium was at the mercy of its foreign competitors and enemies, who promoted and exploited the political and family rivalries among the ruling class. John Cantacuzenus was never popular as an emperor, and feeling against him came to a head when some of his Ottoman mercenaries took the occasion of the destruction of Gallipoli by earthquake to occupy and fortify the city in March 1354. It was their first permanent establishment in Europe, at the key point of the crossing from Asia. In November of the same year John V Palaeologus, encouraged by the Anti-Cantacuzenist Party, forced his way into Constantinople. In December Cantacuzenus abdicated and became a monk. Though his son Matthew, who had by then been crowned as coemperor, fought on for a few years, the dynasty of Cantacuzenus was not perpetuated.

Byzantium became a vassal state of the Turks, pledged to pay tribute and to provide military assistance to the Ottoman sultan. The possession of Constantinople thereafter was disputed by the Emperor's sons and grandsons in a series of revolutions, which were encouraged and sometimes instigated by the Turks, the Genoese, or the Venetians. John V's son Andronicus IV (Andronicus IV Palaeologus), aided by the Genoese and the sultan Murad I, mastered the city for three years (1376–79). He rewarded the Turks by giving back Gallipoli to them, and Murad made his first European capital at Adrianople. The Venetians helped John V to regain his throne in 1379, and the empire was once again divided into appanages under his sons. Only his second son, Manuel (Manuel II Palaeologus), showed any independence of action. For nearly five years, from 1382 to 1387, Manuel reigned as emperor at Thessalonica and laboured to make it a rallying point for resistance against the encroaching Turks. But the city fell to Murad's army in April 1387. When the Turks then drove deeper into Macedonia, the Serbs again organized a counteroffensive but were overwhelmed at Kossovo in 1389.

In 1393 Bayezid completed his conquest of Bulgaria (Bulgar), and soon afterward he laid siege to Constantinople. The blockade was to last for many years. Manuel II, like his father, pinned his hopes of rescue on the West. A great Crusade against the Turks was organized by the King of Hungary, but it was defeated at Nicopolis on the Danube in 1396. In 1399 the French marshal Boucicaut (Boucicaut, Jean II le Meingre), who had been at Nicopolis and had returned to the relief of Constantinople with a small army, persuaded Manuel to travel to western Europe to put the Byzantine case in person. From the end of 1399 to June 1403 the Emperor visited in Italy, France, and England, leaving his nephew John VII in charge of Constantinople. Manuel's journey did something to stimulate Western interest in Greek learning. His friend and ambassador in the West, Manuel Chrysoloras, a pupil of Demetrius Cydones, was appointed to teach Greek at Florence. The Pope instituted a defense fund for Constantinople. Interest and sympathy were forthcoming but little in the way of practical help. During Manuel's absence, however, the Ottomans were defeated at Ankara by the Mongol leader Timur (Tamerlane) in July 1402. Bayezid was captured and his empire in Asia was shattered. His four sons contended with each other to secure possession of the European provinces, which had been little affected by the Mongol invasion, and to reunite the Ottoman dominions. In these wholly unexpected circumstances the Byzantines found themselves the favoured allies first of one Turkish contender, then of another. The blockade of Constantinople was lifted. Thessalonica—with Mount Athos and other places—was restored to Byzantine rule, and the payment of tribute to the sultan was annulled. In 1413 Mehmed I, helped and promoted by the emperor Manuel, triumphed over his rivals and became sultan of the reintegrated Ottoman Empire.

During his reign, from 1413 to 1421, the Byzantines enjoyed their last respite. Manuel II, aware that it could not last, made the most of it by strengthening the defenses and administration of the fragments of his empire. The most flourishing province in the last years was the Despotate of Morea. Its prosperity had been built up first by the sons of John Cantacuzenus (who died there in 1383) and then by the son and grandson of John V—Theodore I and Theodore II Palaeologus. Its capital city of Mistra became a haven for Byzantine scholars and artists and a centre of the last revival of Byzantine culture, packed with churches, monasteries, and palaces. Among its scholars was George Gemistus Plethon, a Platonist who dreamed of a rebirth of Hellenism on Hellenic soil.

When Murad II became sultan, in 1421, the days of Constantinople and of Hellenism were numbered. In 1422 Murad revoked all the privileges accorded to the Byzantines by his father and laid siege to Constantinople. His armies invaded Greece and blockaded Thessalonica. The city was then a possession of Manuel II's son Andronicus, who in 1423 handed it over to the Venetians. For seven years Thessalonica was a Venetian colony, until, in March 1430, the Sultan assaulted and captured it. Meanwhile, Manuel II had died in 1425, leaving his son John VIII (John VIII Palaeologus) as emperor. John, who had already traveled to Venice and Hungary in search of help, was prepared to reopen negotiations for the union of the churches as a means of stirring the conscience of Western Christendom. His father had been skeptical about the benefits of such a policy, knowing that it would antagonize most of his own people and arouse the suspicion of the Turks. The proposal was made, however, at the Council of Florence (Ferrara-Florence, Council of) in 1439, attended by the emperor John VIII, his patriarch, and many Orthodox bishops and dignitaries. After protracted and difficult discussions, they agreed to submit to the authority of Rome. The union of Florence was badly received by the citizens of Constantinople and by most of the Orthodox world. But it had its notable adherents, such as the bishops Bessarion of Nicaea and Isidore of Kiev, both of whom retired to Italy as cardinals of the Roman Church. Bessarion's learning and library helped to encourage further Western interest in Greek scholarship. The union of Florence also helped to stimulate a Crusade against the Turks. Once again it was led by the king of Hungary, Władysław III of Poland, supported by George Branković of Serbia and by János Hunyadi of Transylvania. But there were disagreements among its leaders, and the Christian army was annihilated at Varna in 1444.

The Byzantine collapse and the Ottoman triumph followed swiftly thereafter. In 1448 Constantine XI (Constantine XI Palaeologus) (or XII), the last emperor, left Mistra for Constantinople when his brother John VIII died without issue. His two other brothers, Thomas and Demetrius, continued to govern the Morea, the last surviving Byzantine province. In 1449 Mehmed II (sultan 1444–46 and 1451–81) began to prepare for the final assault on Constantinople. No further substantial help came from the West, and the formal celebration of the union of the churches in Hagia Sophia in 1452 was greeted with a storm of protest. Even in their extremity, the Byzantines would not buy their freedom at the expense of their Orthodox faith. They found the prospect of being ruled by the Turks less odious than that of being indebted to the Latins. When the crisis came, however, the Venetians (Venice) in Constantinople, and a Genoese (Genoa) contingent commanded by Giovanni Giustiniani, wholeheartedly cooperated in the defense of the city. Mehmed II laid siege to the walls in April 1453. His ships were obstructed by a chain that the Byzantines had thrown across the mouth of the Golden Horn. The ships were therefore dragged overland to the harbour from the seaward side, bypassing the defenses. The Sultan's heavy artillery continually bombarded the land walls until, on May 29, some of his soldiers forced their way in. Giustiniani was mortally wounded. The emperor Constantine was last seen fighting on foot at one of the gates.

The last scattered pockets of Byzantine resistance were eliminated within a decade after 1453. Athens fell to the Turks in 1456–58, and in 1460 the two despots of Morea surrendered. Thomas fled to Italy, Demetrius to the Sultan's court. In 1461 Trebizond (Trabzon), capital of the last remnant of Greek empire, which had maintained its precarious independence by paying court to Turks and Mongols alike, finally succumbed; the transformation of the Byzantine world into the Ottoman world was at last complete.