Stephen's father, King Thomas, had great ambitions for him. An attempt to expand into Croatia by marrying Stephen to a wealthy noblewoman failed, and negotiations for a marital alliance with the Sforzas of Milan were abandoned when a more prestigious opportunity presented itself: marriage to the heiress Maria of Serbia. Celebrated in April 1459, it made Stephen the ruler of the remnants of the neighbouring country. The intent was to unite the Kingdom of Bosnia and the Serbian Despotate under Stephen to combat the expanding Ottoman Empire. Stephen's Catholicism made him unpopular in Orthodox Serbia. After ruling it for merely two months, he surrendered it to the encroaching Ottoman forces and fled back to his father's court, which earned him the contempt of the Hungarian king Matthias Corvinus and other Christian rulers in Europe.