Pope Callixtus III added the Feast of the Transfiguration to the calendar to celebrate the important victory of the Hungarian nobleman Janos Hunyadi and the elderly priest St. John of Capistrano at the Siege of Belgrade in July 1456. Breaking the siege, their troops reinforced the Christians at Belgrade, the Muslim Turks were routed, and Islam was stopped from advancing further into Europe.
With the exception of St. John of Capistrano, Hunyadi could find no significant allies to accompany him to Belgrade, but he did enlist the help of young prince Vlad, who agreed to guard the passes into Rumania, thus cutting off the Turk. Without his aid, the battle might not have been won. Vlad was a brutal man whose actions earned him immortality as the fictional vampire, but some Orthodox Christians venerate him as a saint for confronting the Islamic threat to Christian Europe. As we celebrate the Feast of the Transfiguration, we might at least offer a prayer for his soul.