any heavily armed and armoured (armoured vehicle) combat vehicle that moves on two endless metal chains called tracks. Tanks are the principal type of armoured vehicle. Other major types include tracked and wheeled infantry carriers, which were conceived only for transporting troops into action but which also have been used to some extent for fighting; armoured cars, which often resemble the lighter types of tanks but run on wheels; self-propelled guns, some of which are only partly armoured or wheeled; and such specialized vehicles as armoured recovery vehicles, armoured bulldozers, and amphibious landing vehicles.

Tanks are essentially tracked, protected weapon platforms that make the weapons mounted in them more effective by their cross-country mobility and by the protection they provide for their crews. Weapons mounted in tanks have ranged from single rifle-calibre machine guns to, in recent years, long-barreled guns of 120- or 125-millimetre (4.72- or 4.92-inch) calibre.

The use of vehicles for fighting dates to the 2nd millennium BC, when horse-drawn war chariots were used in the Middle East by the Egyptians, Hittites, and others as mobile platforms for combat with bows and arrows. The concept of protected vehicles can be traced back through the wheeled siege towers and battering rams of the Middle Ages to similar devices used by the Assyrians in the 9th century BC. The two ideas began to merge in the battle cars proposed in 1335 by Guido da Vigevano, in 1484 by Leonardo da Vinci, and by others, down to James Cowen, who took out a patent in England in 1855 for an armed, wheeled, armoured vehicle based on the steam tractor.

The outbreak of World War I in 1914 radically changed the situation. Its opening stage of mobile warfare accelerated the development of armoured cars, numbers of which were quickly improvised in Belgium, France, and Britain. The ensuing trench warfare, which ended the usefulness of armoured cars, brought forth new proposals for tracked armoured vehicles. Most of these resulted from attempts to make armoured cars capable of moving off roads, over broken ground, and through barbed wire. The first tracked armoured vehicle was improvised in July 1915, in Britain, by mounting an armoured car body on a Killen-Strait tractor. The vehicle was constructed by the Armoured Car Division of the Royal Naval Air Service, whose ideas, backed by the First Lord of the Admiralty, Winston S. Churchill (Churchill, Sir Winston), resulted in the formation of an Admiralty Landships Committee. A series of experiments by this committee led in September 1915 to the construction of the first tank, called “Little Willie.” A second model, called “Big Willie,” quickly followed. Designed to cross wide trenches, it was accepted by the British Army, which ordered 100 tanks of this type (called Mark I) in February 1916.

Simultaneously but independently, tanks were also developed in France. Like the very first British tank, the first French tank (the Schneider) amounted to an armoured box on a tractor chassis; 400 were ordered in February 1916. But French tanks were not used until April 1917, whereas British tanks were first sent into action on Sept. 15, 1916. Only 49 were available, and their success was limited, but on Nov. 20, 1917, 474 British tanks were concentrated at the Battle of Cambrai (Cambrai, Battle of) and achieved a spectacular breakthrough. These tanks, however, were too slow and had too short an operating range to exploit the breakthrough. In consequence, demand grew for a lighter, faster type of tank, and in 1918 the 14-ton Medium A appeared with a speed of eight miles (13 kilometres) per hour and a range of 80 miles. After 1918, however, the most widely used tank was the French Renault F.T., a light six-ton vehicle designed for close infantry support.

The most effective tank force proved to be the German, composed in 1939 of 3,195 vehicles, including 211 Pz. IVs. What made the German tanks so formidable was that instead of being divided between various infantry and cavalry tank units they were all concentrated and used in massed formations in the panzer divisions (panzer division). The successes of the panzer divisions during the first two years of World War II led the major armies to reorganize most of their tanks into similar formations; this resulted in a dramatic increase in production.

The campaigns of 1939–41, in which armoured forces played such an important role, also intensified the technical development of tanks and other armoured vehicles. The German Pz. IV and Soviet T-34 were rearmed in 1942 with longer-barreled, higher-velocity guns; soon afterward these began to be displaced by more powerfully armed tanks. In 1943 the Germans introduced the Panther medium tank with a long 75-millimetre gun having a muzzle velocity of 3,070 feet (936 metres) per second, compared with 1,260 feet per second for the original Pz. IV and 2,460 feet per second for its 1942 version. The 43-ton Panther weighed almost twice as much as its predecessor and was correspondingly better armoured. Germany also introduced the still more powerful Tiger tank, armed with an 88-millimetre gun. Its final version (Tiger II), at 68 tons, was to be the heaviest tank used during World War II. To oppose it, the Russians brought out the JS, or Stalin, heavy tank, which appeared in 1944 armed with a 122-millimetre gun. Its muzzle velocity was lower than that of the German 88-millimetre guns, however, and it weighed only 46 tons. At about the same time the T-34 was rearmed with an 85-millimetre gun.

The turretless-tank type of vehicle originated with the Sturmgeschutz, or assault gun, introduced by the German army for infantry support but subsequently transformed into more versatile vehicles particularly suited for destroying enemy tanks. No such vehicles were produced in Britain or the United States. Throughout the war, however, the British army retained a specialized category of infantry tanks, such as the Churchill, and of cruiser tanks, such as the Crusader and Cromwell (Cromwell tank). The former were well-armoured, and the latter were fast, but none was well-armed compared to German and Soviet tanks. As a result, during 1943 and 1944, British armoured divisions were mostly equipped with U.S.-built M4 Sherman (Sherman tank) medium tanks. The M4 was preceded by the mechanically similar M3 medium, which was also armed with a medium-velocity 75-millimetre gun but mounted it in the hull instead of the turret, because this could be put into production more quickly when tanks were urgently required in 1940 and 1941. Production of the M4 began in 1942, and eventually 49,234 were built, making it the principal tank of U.S. and other allied armoured forces. Successful when first introduced, it was by 1944 no longer adequately armed and should have been replaced by a new medium tank. But the U.S. Army, like the British, adhered to the fallacious doctrine that armoured divisions should confine themselves to exploitation of infantry breakthroughs and did not, therefore, need powerfully armed tanks. Only toward the end of the war did the U.S. Army introduce a few M26 Pershing heavy tanks with a 90-millimetre gun comparable to that of the original German Tiger. Similarly, the British army introduced the prototypes of the Centurion tank with a 76-millimetre gun comparable to that of the German Panther. Otherwise, U.S. and British tanks were well behind the German and Soviet tanks in their gun power.

Increases in gun calibre are well illustrated by the British Centurion, which started in 1945 with a 76-millimetre gun but in 1948 was rearmed with an 83.8-millimetre gun and in 1959 with an even more powerful 105-millimetre gun. Moreover, during the 1950s the capabilities of British tank units were augmented by a small number of Conqueror heavy tanks armed with 120-millimetre guns, and in the early 1970s the Centurions were entirely replaced by Chieftains armed with a new and more effective 120-millimetre gun.

Similar increases took place in the calibre of Soviet tank guns. After World War II the basic T-34/85 tanks armed with 85-millimetre guns were replaced by T-54 and T-55 tanks armed with 100-millimetre guns. They were followed in the 1960s by the T-62, with a 115-millimetre gun, and in the 1970s and '80s by the T-64, T-72, and T-80, all with 125-millimetre smoothbore guns. The JS-3 and T-10 heavy tanks with their less powerful 122-millimetre guns had by then been withdrawn. This left the Soviet army in the same position as others of having a single type of battle tank as well armed as contemporary technology would allow.

The same 105-millimetre gun was adopted for the Pz. 61 and Pz. 68 tanks produced in Switzerland, the West German Leopard 1, the Swedish S-tank, the Japanese Type 74, and the Mark 1 and 2 versions of the Israeli Merkava. It was also retained in the original version of the U.S. M1 tank developed in the 1970s, but the subsequent M1A1 version of the 1980s was rearmed with a 120-millimetre gun originally developed in West Germany for the Leopard 2 tank. The British Challenger, introduced in the 1980s, was also armed with 120-millimetre guns, but these were still of the rifled type.

After the middle of World War II many other tanks were made amphibious by collapsible flotation screens, which, when erected, allowed even relatively heavy tanks to float. This method was first used with M4 medium tanks during the D-Day landings in Normandy in 1944. Later, flotation screens were permanently installed on the Swedish S-tank, the U.S. M551 Sheridan, and the Scorpion light reconnaissance tank introduced in 1969 by the British army.

An entirely different problem was posed by amphibious landings from the open seas; to solve it the U.S. Marine Corps developed the Landing Vehicle Tracked, or LVT. Originally built in 1941 as an unarmoured cargo carrier, the LVT quickly acquired armour. Two types evolved: an armoured amphibious personnel and cargo carrier, and a turreted amphibious gun-vehicle for close fire support during landing operations. Altogether 18,620 LVTs were built during World War II; these played a prominent role in the Pacific campaigns from Guadalcanal onward. After World War II, LVTs were successfully used in Korea, notably for the 1950 Inch'ŏn landing. Two new models were built between 1951 and 1957: an LVTP-5 amphibious carrier, capable of carrying as many as 37 men, and an LVTH-6 armed with a turret-mounted 105-millimetre howitzer. They were followed in the 1970s by the 22.8-ton LVTP-7, which incorporated several improvements, the most important being a boatlike hull with a stern instead of bow loading ramp and two water-jet propulsion units that greatly improved its performance in comparison with that of the earlier LVTs (which were propelled in water as well as on land by means of their tracks). At the same time the LVTP-7 retained the seagoing qualities of the earlier LVTs, which could negotiate rough seas and Pacific surf in contrast to other amphibious vehicles intended primarily for crossing inland water obstacles. The use of water-jet propulsion units in the LVTP-7, however, had been preceded by their use in several amphibious reconnaissance vehicles, including the Soviet PT-76.

Self-propelled guns are field artillery, antitank guns, or antiaircraft guns mounted on and fired from tracked or wheeled vehicles. The vehicles are armoured to varying degrees.

In 1955 the M75 began to be replaced by the M59, which was similar in appearance but was less expensive and could swim across calm inland waters. In 1960 came the M113, which had a lower silhouette and was considerably lighter, owing partly to the use of aluminum armour. The M113 was in fact the first aluminum-armoured vehicle to be put into large-scale production. After its appearance, several other armoured carriers, light tanks, and self-propelled guns were built with aluminum armour. Within 30 years more than 76,000 M113 carriers and their derivatives had been produced, making them the most numerous armoured vehicles outside the Soviet bloc. M113 carriers were used extensively in the Vietnam War, often as combat vehicles, although they were not designed for this and were at a disadvantage in spite of the addition of roof-mounted machine guns with shields.

In addition to tracked armoured carriers or infantry fighting vehicles, which were intended to cooperate closely with tanks, most armies also developed wheeled armoured carriers for more general use. Examples included the VAB of the French army and the BTR-60, -70, and -80 of the Soviet army.

Tanks and armoured vehicles are discussed in Richard M. Ogorkiewicz, Armour: A History of Mechanized Forces (1960, reissued as Armoured Forces: A History of Armoured Forces and Their Vehicles, 1970); and Design and Development of Fighting Vehicles (1968), on the technical aspects. The history of various types of vehicles from World War I to the end of World War II is presented in Duncan Crow (ed.), AFVs of World War One (1970), British AFVs, 1919–40 (1970), British and Commonwealth AFVs, 1940–46 (1971), American AFVs of World War II (1972), and Armored Fighting Vehicles of Germany: World War II (1973). Peter Chamberlain and Hilary L. Doyle, Encyclopedia of German Tanks of World War Two: A Complete Illustrated Directory of German Battle Tanks, Armoured Cars, Self-Propelled Guns, and Semi-tracked Vehicles, 1933–1945 (1978), provides a comprehensive pictorial record. Duncan Crow (ed.), Modern Battle Tanks (1978), focuses on the period between 1950 and 1970. For particular types of tanks, see Walter J. Spielberger, From Half-Track to Leopard 2: The Complete Illustrated History of the Krauss-Maffei Ordnance Department (1979; originally published in German, 1979); John Milsom, Russian Tanks, 1900–1970: The Complete Illustrated History of Soviet Armoured Theory and Design (1970); and R.P. Hunnicut, Sherman: A History of the American Medium Tank (1978), Patton: A History of the American Main Battle Tank (1984), and Firepower: A History of the American Heavy Tank (1988). For current information on developments in technology, see Jane's Armour and Artillery (annual) and Jane's Armoured Fighting Vehicle Systems (annual).Richard Marian Ogorkiewicz