It is believed that the dynastic disputes that soon erupted between him and his uncle Kęstutis and his cousin Vytautas the Great were largely inspired by Skirgaila.

Skirgaila was the chief supporter of his brother Jogaila and helped him to imprison both Kęstutis and Vytautas in Kreva castle during the Lithuanian Civil War (1381–1384).

When Jogaila was preparing for the Union of Kreva, Skirgaila was actively involved in the negotiations and even headed a diplomatic mission to Poland.

Later Skirgaila attacked Polatsk; his first expedition in October was unsuccessful, but the next on March 1387 resulted in Andrei's capture and death of his son Simeon, who was killed in a battle.

[3] Next month Skirgaila was invested in Polatsk and once again pledged his loyalty to Jogaila, Jadwiga and Polish Crown, promising return of his land in case of his heirless death.