In 1389, Władysław's rule in Lithuania faced a revived challenge from Vytautas, who resented the power given to Skirgaila in Lithuania at the expense of his own patrimony. Vytautas started a civil war in Lithuania, aiming to become the Grand Duke. On 4 September 1390, the joint forces of Vytautas and Grand Master Konrad von Wallenrode of the Teutonic Order, laid siege to Vilnius, which was held by Władysław's regent Skirgaila with combined Polish, Lithuanian and Ruthenian troops. Although the Knights lifted the siege of the castle after a month, they reduced much of the outer city to ruins. This bloody conflict was eventually brought to a temporary halt in 1392 with the Treaty of Ostrów, by which Władysław handed over the government of Lithuania to his cousin in exchange for peace: Vytautas was to rule Lithuania as the grand duke ("magnus dux") until his death, under the overlordship of the Supreme Duke ("dux supremus") in the person of the Polish monarch. Skirgaila was moved from the Duchy of Trakai to become prince of Kiev. Vytautas initially accepted his status but soon began to pursue Lithuania's independence from Poland.