Livonian Brothers of the Sword in the context of Bishopric of Dorpat

The State of the Teutonic Order (German: Staat des Deutschen Ordens, pronounced [ˈʃtaːt dɛs ˌdɔʏtʃn̩ ˈʔɔʁdn̩s] ) was a theocratic state located along the southeastern shore of the Baltic Sea in northern Europe. It was formed by the knights of the Teutonic Order during the early 13th century Northern Crusades in the region of Prussia. In 1237, the Livonian Brothers of the Sword merged with the Teutonic Order of Prussia and became known as its branch – the Livonian Order (while their state, Terra Mariana, covering present-day Estonia, Latvia, and a small part of Russia, became part of the State of the Teutonic Order). At its greatest territorial extent during the early 15th century, the State encompassed Chełmno Land, Courland, Gotland, Livonia, Estonia, Neumark, Pomerelia (Gdańsk Pomerania), Prussia and Samogitia.

Following the battles of Grunwald in 1410 and Wilkomierz in 1435, the State fell into decline. After losing extensive territories in the imposed Peace of Thorn in 1466, the extant territory of its Prussian branch became known as Monastic Prussia (Polish: Prusy zakonne) or Teutonic Prussia (Polish: Prusy krzyżackie). It existed until 1525 as a fiefdom of the Polish Crown. The Livonian branch joined the Livonian Confederation and continued to exist as part of it until 1561.

Livonia, known in earlier records as Livland, is a historical region on the eastern shores of the Baltic Sea. It is named after the Livonians, who lived on the shores of present-day Latvia.

By the end of the 13th century, the name was extended to most of present-day Estonia and Latvia, which the Livonian Brothers of the Sword had conquered during the Livonian Crusade (1193–1290). Medieval Livonia, or Terra Mariana, reached its greatest extent after the Saint George's Night Uprising (1343–1345), which forced Denmark to sell the Duchy of Estonia (northern Estonia conquered by Denmark in the 13th century) to the State of the Teutonic Order in 1346. Livonia, as understood after the retreat of Denmark in 1346, bordered on the Gulf of Finland in the north, Lake Peipus and Russia to the east, and Lithuania to the south.

The history of Latvia began around 9000 BC with the end of the last glacial period in northern Europe. Ancient Baltic peoples arrived in the area during the second millennium BC, and four distinct tribal realms in Latvia's territory were identifiable towards the end of the first millennium AD. Latvia's principal river Daugava, was at the head of an important trade route from the Baltic region through Russia into southern Europe and the Middle East that was used by the Vikings and later Nordic and German traders.

In the early medieval period, the region's peoples resisted Christianization and became subject to attack through the Livonian Crusade. Latvia's capital city Riga, founded in 1201 by Germans at the mouth of the Daugava, became a strategic base in a papally-sanctioned conquest of the area by the Livonian Brothers of the Sword. It was to be the first major city of the southern Baltic and, after 1282, a principal trading center in the Hanseatic League.

Terra Mariana (Medieval Latin for 'Land of Mary') was the formal name for Medieval Livonia or Old Livonia. It was formed in the aftermath of the Livonian Crusade, and its territories were composed of present-day Estonia and Latvia. It was established on 2 February 1207, as a principality of the Holy Roman Empire, and lost this status in 1215 when Pope Innocent III proclaimed it as directly subject to the Holy See.

The papal legate William of Modena divided Terra Mariana into feudal principalities: the Duchy of Estonia (dominum directum to the king of Denmark); the Archbishopric of Riga; the Bishopric of Courland; the Bishopric of Dorpat; the Bishopric of Ösel–Wiek; and territories under the military administration of the Livonian Brothers of the Sword. After the 1236 Battle of Saule, the surviving members of the Brothers merged in 1237 with the Teutonic Order of Prussia and became known as the Livonian Order. In 1346 the Livonian Order bought the Duchy of Estonia from Denmark.