Also spelled Calixtus III. Reigned from April 8, 1455 to August 6, 1458. Born on December 31, 1378 at Xàtiva, Valencia, Spain as Alphonso de Borgia; died on August 6, 1458 at Rome, Italy. He was Bishop of Valencia, then cardinal. As pope he organized Christian Europe against the Turks who were defeated at Belgrade in 1456. He revised the trial of Saint Joan of Arc and had her innocence proclaimed.