雅盖沃
Both Władysław II Jagiełło, King of Poland, and Vytautas, Grand Duke of Lithuania, sought to renew the Polish–Lithuanian union, which had existed since 1385. In 1399, Queen Jadwiga of Poland died due to childbirth complications, leaving Władysław II Jagiełło king of a foreign land and without an heir. If Polish nobles forced Władysław II Jagiełło to abdicate the throne, he would return to Lithuania demanding the throne of the Grand Duke. Vytautas would be forced either to return to Duchy of Trakai or launch another civil war. The same year Vytautas suffered a major defeat in the Battle of the Vorskla River against the Golden Horde and faced rebellions in the Principality of Smolensk, Republic of Pskov, and Velikiy Novgorod.