organization of crusading knights that began the successful conquest and Christianization of Livonia (most of modern Latvia and Estonia) between 1202 and 1237.

After German merchants from Lübeck and Bremen acquired commercial interests in the lands around the mouth of the Dvina River (mid-12th century), German missionaries entered the region. In 1202 the third bishop of Livonia, Albert von Buxhoevden, founded the Order of the Brothers of the Sword, with the pope's permission, as a permanent military body in Livonia to protect the church's conquests and to forcibly convert the native pagan tribes to Christianity.

Consecrated by the pope in 1204, the order adopted the rules of the Knights Templar; the order's knights (called Knights of the Sword because their white cloaks were decorated with red crosses and swords) were required to be of noble birth and to take vows of obedience, poverty, and celibacy. They lived in district castles, each of which was ruled by its own council and a military chief, who was chosen by the order's grand master. The grand master, who served for life, was selected by the knights' general assembly, which also elected the order's other officials at its annual sessions. In addition to knights, the order's membership included soldiers, artisans, and clerics.

By 1206 the order had firmly established itself as the dominant power in the land of the Livs, the Finno-Ugrian people dwelling near the mouths of the Dvina and Gauja rivers, and by 1217 it had conquered not only the neighbouring Latvian tribes north of the Dvina but also southern Estonia. It then began the conquest of the lands south of the Dvina but encountered strong resistance from their inhabitants, the Curonians (Kurs) and the Semigallians. In September 1236 while the order's army, heavily burdened with booty, was returning through Semigallia from a raid in Lithuanian Samogitia, a combined force of Semigallians and Samogitians inflicted a disastrous defeat upon them (Battle of Saule), killing the grand master, Volquin, and effectively destroying the knights' military might. The order, which had been reprimanded by both the Holy Roman emperor and the pope for indiscriminately using brutal tactics against converts as well as heathens and which appeared by this time to be more concerned with establishing its own feudal domain than with gathering converts for the church, was then forced by the pope to disband and reorganize as a branch (1237) of the Teutonic Knights, whose main base was in Prussia and whose grand master thenceforth appointed the provincial master (Landmeister) of Livonia. The Livonian Knights continued the conquest of Livonia and ruled the region as an autonomous order again from 1525. Livonia, however, was divided and the order dissolved in 1561.