Švitrigaila commanded a force of about 11,000 men: Lithuanians and Orthodox Ruthenians from
Polotsk,
Vitebsk,
Smolensk,
Kiev,
Volhynia, Livonian Knights and their mercenaries, at least 500 Tatars from the Golden Horde, and a few Teutonic Knights. There might have been some
Hussites on his side as he enlisted his nephew
Sigismund Korybut, a distinguished military leader during the
Hussite Wars. Forces of Sigismund Kęstutaitis were probably smaller. His son
Michael commanded Lithuanian troops from
Samogitia,
Podlaskie,
Hrodna,
Minsk, and
Jakub Kobylański was in charge of Polish forces (4,000 troops). Švitrigaila gathered his forces in
Vitebsk and marched towards
Braslaw where he joined with the Livonian forces on August 20. The plan was to march Trakai and Vilnius. The opponents met about south of
Vilkmergė. At first, the armies were separated by Lake Žirnajai and a marshy creek (Žirnaja or Vintara). The armies did not engage each other. After two days, Švitrigaila and Livonian Grand Master
Franco Kerskorff decided to change their position and move north towards Vilkmergė. As the army regrouped and was separated by a rivulet, it was attacked by Sigismund Kęstutaitis. Švitrigaila's army was split in half; the first to fall was the flag of Livonian marshal Werner von Nesselrode. In the ensuing panic, Švitrigaila's army was soundly defeated. Švitrigaila managed to escape to
Polotsk with about 30 followers. Kerskorff was killed in the battle along with his marshal and several
komturs. Korybut was severely wounded and captured. He died a few days later; historians speculate whether he died of the wounds, was drowned, or poisoned. Many others, including Duke Yaroslav, son of
Lengvenis, and imperial envoy Sigismund de Rota, were killed. Many knights, including a reserve unit that was late to battle, were taken captive. Others drowned in the
Šventoji River. The victors hunted down the survivors for 15 days. ==Aftermath==