Hunyadi family
A feud with the Hungarian Hunyadi family followed, embittered by John Hunyadi's failed attack on the forces of the Ottoman Empire at the Battle of Varna in 1444—while Ulrich remained idle—and Hunyadi's refusal to recognize Ulrich's claim to Bosnia on the death of King Tvrtko II (1443). In 1446 Hunyadi, now regent of Hungary, harried the Celje territories in Croatia-Slavonia; however his power was broken at the Second Battle of Kosovo in 1448, and Count Ulrich was able to lead a successful crusade, nominally in the Habsburg interest, into Hungary (1450).