Grand Duchy of Lithuania
Consolidation of the Lithuanian lands began in the 12th century but the Baltic tribes were first united by Mindaugas, Grand Duke of Lithuania (c.1235-1263). Mindaugas was crowned King of Lithuania in 1251 and is widely considered the founder of the Lithuanian state. A general unrest broke out ater his death in 1263 but the Grand Duchy did not disintegrate. Gediminas (1316-1341) inherited cohesive territory which formed a base for future rise of Lithuania and extended the frontiers of his duchy to southwest and southeast. The Lithuanian territorial expansion was relatively peaceful because the East Slavic princes voluntarily subordinated themselves to Lithuania due to the Mongol threat as well as due to wide autonomy that was granted to non-Lithuanian peoples by the Lithuanian Grand Dukes.
Territorial expansion started by Gediminas was pursued by his sons Algirdas (Olgerd) and Kestutis who ruled jointly between 1341 and 1376. Lithuanian domain was extended to the Baltic Sea on the north and to the Black Sea on the south. Thus Jogaila (1377-1434) became the Grand Duke of one of the largest states in Medieval Europe which also encompassed the territory of today’s Ukraine, Belarus and part of western Russia. In 1386, Jogaila converted to Christianity, married Jadwiga of Poland and was crowned King of Poland as Wladyslaw II Jagiello creating the Polish-Lithuanian union which lasted for four centuries.