Louis joined a crusade against the pagan Lithuanians in December 1344. The crusadersincluding John of Bohemia, Charles of Moravia, Peter of Bourbon, and William of Hainaut and Holland laid siege to Vilnius. However, a Lithuanian invasion of the lands of the Teutonic Knights forced them to lift the siege. Louis returned to Hungary in late February 1345. He dispatched Andrew Lackfi to invade the lands of the Golden Horde in retaliation for the Tatars' earlier plundering raids against Transylvania and the Szepesség (now Spiš in Slovakia). Lackfi and his army of mainly Székely warriors inflicted a defeat on a large Tatar army. Thereafter the Golden Horde's control of the lands between the Eastern Carpathians and the Black Sea weakened. A conflict between Louis's uncle and father-in-law (Casimir III of Poland and Charles of Moravia) led to a war between Poland and Bohemia in April. In this war Louis supported his uncle with reinforcements in accordance with the agreement of 1339.