In 1456, Skanderbeg's ally, Janos Hunyadi, died, and his son, Mathias Corvinus, was crowned King of Hungary. Hunyadi had been an advocate for an offensive war against the Ottoman Empire, whereas the Hungarian nobility and his son promoted a defensive war. The next year, however, George Kastrioti Skanderbeg defeated a sizable Ottoman force at the Battle of Albulena (Ujëbardha). Rome had been desperately waiting for such a victory after the Siege of Belgrade, as Pope Calixtus III had wanted to assure himself of the feasibility of a crusade before declaring one. Calixtus thus named Skanderbeg the Captain-General of the Curia; to secure the pope's interests, Skanderbeg sent twelve Turkish prisoners of war that had been captured at Albulena to Rome. Despite seeing his forces defeated the year before, Sultan Mehmed II prepared another force to be sent into Albania. The country had been obstructing his ambitions for empire in the West and he grew restless to defeat Skanderbeg. Skanderbeg sent delegations to several Western European states to convince them to stop fighting each other and unite for Calixtus' crusade.