When Grand Duke of Lithuania
Jadwiga of Poland and was crowned as King of Poland in 1386, he appointed his unpopular brother
Skirgaila as viceroy for Lithuania. Vytautas seized the opportunity to renew his struggle for power and started the
Lithuanian Civil War (1389–92). He allied himself with the Teutonic Knights, promising them
Samogitia. However, Jogaila and Vytautas reconciled in 1392 by signing the
Treaty of Astrava. The Knights, betrayed by Vytautas, invaded Lithuania in 1394 and unsuccessfully besieged
Vilnius for three weeks.
 The invaders were driven away by joint Lithuanian and Polish forces demonstrating that the old raids were no longer effective against the new Polish–Lithuanian alliance.
 A truce between the Knights and Vytautas was signed in 1396. Vytautas needed to secure his western front as he was planning a massive campaign against the
Golden Horde, which resulted in a disaster at the
Battle of the Vorskla River in 1399.