started organizing a wider anti-Polish coalition. In June 1431, an agreement was reached with the Teutonic Knights: the Knights declared war and without much opposition invaded Poland, whose forces where engaging Švitrigaila in Volhynia. In September a two-year truce between Poland, Lithuania, and the Teutonic Knights was signed in Staryi Chortoryisk. It was more favorable to Poland and it is not clear why Švitrigaila agreed to it. However, the truce did not solve the underlying dispute. The war turned into diplomatic struggle: Poland sought to turn Lithuanian nobles against Švitrigaila. Coup and civil war Conspirators, led by Sigismund Kęstutaitis, attacked Švitrigaila and his escort, who were staying in Ashmyany for the night of 31 August 1432. Švitrigaila managed to escape to Polotsk while his pregnant wife Anna of Tver was detained. It is unclear what groups supported Sigismund and why. Possibly Lithuanian nobles were dissatisfied with favors Švitrigaila showed to Orthodox dukes, but before the coup no such opposition manifested itself. Sigismund, who did not play a major role in Lithuanian politics before the coup and who initially supported Švitrigaila, became the Grand Duke and resumed policy of union with Poland. Lithuania was divided into two camps: supporters of Sigismund (Lithuanian lands, Samogitia, Podlaskie, Hrodna, Minsk) to the west, and supporters of Švitrigaila (Polotsk, Vitebsk, Smolensk, Kiev [Kyiv], Volhynia) to the east. Three years of devastating hostilities began. Švitrigaila enlisted help from Sayid Ahmad I, Khan of the Golden Horde. Both sides suffered heavy losses (see Battle of Ashmyany) and final victory in the Battle of Wiłkomierz went to Sigismund in 1435. After the defeat, Švitrigaila fled to Polotsk. Losing his influence in the Slavic principalities, he attempted to reconciled with Poland in September 1437: he would rule lands that still supported him (chiefly Kiev and Volhynia) and after his death the territories would pass to the King of Poland. However, Polish Senate did not ratify this treaty under strong protest from Sigismund. Švitrigaila retreated to Wallachia in 1438. Later years In 1440, Sigismund Kęstutaitis was assassinated by nobles who supported Švitrigaila, and Švitrigaila returned to rule Podolia and Volhynia. At the age of 70 (or 85, according to some sources), he was too old to resume his struggle for the Lithuanian throne and more importantly had no support from the Council of Lords led by Jonas Goštautas, that in June 1440 elected Casimir Jagiellon, brother of Polish King Władysław