The Ottomans' attempt to conquer new territories led to a better organized policy against them. The temporary union of the Eastern and Western Churches proclaimed by the Council of Florence in 1439 also created a favorable background for the concentration of Christian forces. Christendom found its champion in John Hunyadi who gained a series of victories over the Ottomans after 1441. For instance, in 1442 he routed an Ottoman army that had been devastating Transylvania. Through his last victory over Mehmed II at the siege of Belgrade (in modern Serbia) in 1456, he saved the kingdom from Ottoman occupation for several decades. During the reign of his son, Matthias I of Hungary (1458–1490), the Ottomans launched only one serious attack against Transylvania in 1479 when they were defeated at Câmpul Pâinii.