Livonian Order in the context of Medieval Livonia

Mindaugas (c. 1203 – 12 September 1263) was the first known Grand Duke of Lithuania and the only crowned King of Lithuania. Little is known of his origins, early life, or rise to power; he is mentioned in a 1219 treaty as an elder duke, and in 1236 as the leader of all the Lithuanians. The contemporary and modern sources discussing his ascent mention strategic marriages along with banishment or murder of his rivals. He extended his domain into regions southeast of Lithuania proper during the 1230s and 1240s. In 1250 or 1251, during the course of internal power struggles, he was baptised as a Roman Catholic; this action enabled him to establish an alliance with the Livonian Order, a long-standing antagonist of the Lithuanians. By 1245, Mindaugas was already being referred to as "the highest king" in certain documents. During the summer of 1253, he was crowned king, ruling between 300,000 and 400,000 subjects, and got nicknamed as Mindaugas the Sapient by the Livonians.

While Mindaugas's ten-year reign as king was marked by many state-building accomplishments, his conflicts with relatives and other dukes continued. The western part of Lithuania – Samogitia – strongly resisted the alliance's rule. His gains in the southeast were challenged by the Tatars. He broke peace with the Livonian Order in 1261, possibly renouncing Christianity, and was assassinated in 1263 by his nephew Treniota and another rival, Duke Daumantas of Pskov. His three immediate successors were assassinated as well. The disorder was not resolved until Traidenis gained the title of grand duke c. 1270.

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.

The Lithuanian Crusade was a series of campaigns by the Teutonic Order and the Livonian Order under the pretext of forcibly Christianizing the pagan Grand Duchy of Lithuania. The Livonian Order occupied Riga in 1202 and in the 1230s they settled in Chełmno Land, a fief of Poland. They first conquered other neighboring Baltic tribes— proto-Latvians (Curonians, Semigallians, Latgalians, Selonians) and Old Prussians—in the Livonian Crusade and Prussian Crusade.

The first raid against the Lithuanians and Samogitians was in 1208. From then on, the orders played a key role in Lithuanian politics, but they were not a direct threat until the 1280s. By that time, the Grand Duchy of Lithuania was already a centralized state and could mount defenses. For the next century, the order organized annual colonialist reise (raids) into Samogitian and Lithuanian lands, without great success but at immense human cost. Border regions in Samogitia and Suvalkija became sparsely inhabited wilderness due to ethnic cleansing, although the order gained very little territory. The resulting wars between the Teutonic Order and Lithuania were one of the longest conflicts in the history of Europe.

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.

The Battle of Wiłkomierz (see other names) took place on September 1, 1435, near Ukmergė in the Grand Duchy of Lithuania. With the help of military units from the Kingdom of Poland, the forces of Grand Duke Sigismund Kęstutaitis soundly defeated Švitrigaila and his Livonian allies. The battle was a decisive engagement of the Lithuanian Civil War (1432–1438). Švitrigaila lost most of his supporters and withdrew to southern Grand Duchy; he was slowly pushed out and eventually made peace. The damage inflicted upon the Livonian Order has been compared to the damage of Battle of Grunwald upon the Teutonic Order. It was fundamentally weakened and ceased to play a major role in Lithuanian affairs. The battle can be seen as the final engagement of the Lithuanian Crusade.

The Battle on the Ice, also known as the Battle of Lake Peipus, took place on 5 April 1242. It was fought on the frozen Lake Peipus when the united forces of the Republic of Novgorod and Vladimir-Suzdal, led by Prince Alexander Nevsky, emerged victorious against the forces of the Livonian Order and Bishopric of Dorpat, led by Bishop Hermann of Dorpat.

The outcome of the battle has been traditionally interpreted by Russian historiography as significant for the balance of power between Western Catholicism and Eastern Orthodox Christianity. It is disputed whether the battle should be considered a "crusade" or not, and whether it therefore represented a significant defeat for the Catholic forces during the Northern Crusades, thus bringing an end to their campaigns against the Orthodox Novgorod Republic and other Rus' territories. Estonian historian Anti Selart asserts that the crusades were not an attempt to conquer Rus', but still constituted an attack on the territory of Novgorod and its interests.