The Battle of Wiłkomierz (see other names) took place on September 1, 1435, near Ukmergė in the Grand Duchy of Lithuania. With the help of military units from the Kingdom of Poland, the forces of Grand Duke Sigismund Kęstutaitis soundly defeated Švitrigaila and his Livonian allies. The battle was a decisive engagement of the Lithuanian Civil War (1432–1438). Švitrigaila lost most of his supporters and withdrew to southern Grand Duchy; he was slowly pushed out and eventually made peace. The damage inflicted upon the Livonian Order has been compared to the damage of Battle of Grunwald upon the Teutonic Order. It was fundamentally weakened and ceased to play a major role in Lithuanian affairs. The battle can be seen as the final engagement of the Lithuanian Crusade. Names The battle is also known as the Battle of Vilkomir or Ukmergė after Ukmergė/Vilkmergė, the nearest large settlement. It is also known as Battle of Święta/Šventoji after the Šventoji River that flows near the battle site. In Lithuanian, the battle is known as the Battle of Pabaiskas. The word "pabaiskas" is derived from Polish "pobojowisko" literally meaning "battle site" or "place where a battle was fought". It came into use as a name for the town of Pabaiskas which grew around the Church of the Holy Trinity built at the site in 1436–40 by Sigismund Kęstutaitis. Background In October 1430, Vytautas the Great died without an heir. The Lithuanian nobles elected Švitrigaila, Jogaila's brother and Vytautas' cousin, as the new Grand Duke without first consulting with Poland. This violated the Union of Horodło of 1413, and outraged the Polish nobles. Švitrigaila prepared for war and enlisted the Teutonic Knights, Moldavia, and the Golden Horde as his allies. Sigismund Kęstutaitis assumed power in Lithuania when he deposed Švitrigaila in a coup on August 31, 1432. Švitrigaila escaped, established himself in Polotsk, and rallied his supporters from Slavic lands of the Grand Duchy against Sigismund. The Teutonic Knights secretly supported Švitrigaila chiefly through its branch in Livonia. Švitrigaila and Sigismund were now engaged in a destructive civil war. In December 1432, their armies fought in the Battle of Ashmyany; Švitrigaila was defeated, but the victory was not decisive. In 1433, together with the Livonian knights, Švitrigaila raided Lida, Kreva, Eišiškės and devastated the surrounding areas near Vilnius, Trakai, and Kaunas. After Jogaila's death in 1434, the Teutonic Knights resumed their war against Poland. In