The Battle of the Vorskla River was a great battle in the medieval history of Eastern Europe. It was fought on August 12, 1399, between the Kazakh-Tatars of the Golden Horde, under Edigu and Temür Qutlugh, and the armies of Tokhtamysh and a large Crusader force led by the Grand Duke Vytautas of Lithuania. The battle ended in a decisive Kazakh-Tatar victory. Background In late 1380s the relationship between Tokhtamysh, Khan of the Golden Horde, and his former master, Timur, was growing tense. In 1395, after losing the Tokhtamysh–Timur war, Tokhtamysh was dethroned by the party of Khan Temur Qutlugh and Emir Edigu, supported by Timur. Tokhtamysh escaped to the Grand Duchy of Lithuania and asked Vytautas for assistance in retaking the Horde in exchange for surrendering his suzerainty over Ruthenian lands. This development was in harmony with Vytautas' ambitions to become ruler of all Ruthenian lands. A surviving iarlyk shows that Tokhtamysh had asked for Polish–Lithuanian assistance previously in 1393. Vytautas' expeditions Vytautas gathered a large army which included Lithuanians, Ruthenians, Poles, Moldavians, and Wallachians. To enlist support from the Teutonic Knights, Vytautas signed the Treaty of Salynas, surrendering Samogitia to the Knights. Vytautas's son-in-law, Vasily I of Moscow, formally a Tatar vassal, did not join the coalition. The joint forces organized three expeditions into Tatar territories, in 1397, 1398, and 1399. The first expedition reached the Black Sea and Crimea. Vytautas took several thousand captives without much opposition. Half of these captives were settled near Trakai and awarded privileges to practice their faith. Communities of their descendants, Lipka Tatars and Crimean Karaites (Karaims), survive to this day. In 1398, the army of Vytautas moved from the Dnieper River and attacked northern Crimea, reaching as far east as the River Don. In order to strengthen his position, Vytautas built a castle at the mouth of Dnieper. Inspired by their successes, Vytautas declared a "Crusade against the Tatars" and in May 1399 received blessing from Pope Boniface IX. The papal blessing for the crusade was an important political achievement for Lithuania, a country converted to Christianity only in 1387 and the subject of a hundred-year crusade. The campaign was organized from Kiev. In 1399, the army of Vytautas once again moved against the Horde along the Dnieper River. On August 5, his army met the Tatars at the Vorskla River just north of Poltava (almost same location as the Battle