John of Capistrano, a Franciscan friar and papal inquisitor, started to preach an anti-Ottoman crusade in Hungary in February 1456. The Diet ordered the mobilization of the armed forces in April, but most barons failed to obey and continued to war against their local adversaries, including the Hussites in Upper Hungary. Before departing from Transylvania against the Ottomans, Hunyadi had to face a rebellion by the Vlachs in Fogaras County. He also supported Vlad Draculaa son of the late Vlad Draculto seize the Wallachian throne from Vladislav II.