The first battle between the forces of Švitrigaila and Sigismund Kęstutaitis is fought near the town of Oszmiana (Ashmyany), launching the most active phase of the Lithuanian Civil War.
Švitrigaila (before 1370 – 10 February 1452; sometimes spelled Svidrigiello) was the Grand Duke of Lithuania from 1430 to 1432. He spent most of his life in largely unsuccessful dynastic struggles against his cousins Vytautas and Sigismund Kęstutaitis.