The last crusade, the "Crusade of 1456", was organized to counter the expanding Ottoman Empire and lift the Siege of Belgrade, and was led by John Hunyadi and Giovanni da Capistrano. The siege eventually escalated into a major battle, during which Hunyadi led a sudden counterattack that overran the Turkish camp, ultimately compelling the wounded Sultan Mehmet II to lift the siege and retreat. The siege of Belgrade has been characterized as having "decided the fate of Christendom". The noon bell ordered by Pope Callixtus III commemorates the victory throughout the Christian world to this day.