Callixtus III

Pope Callixtus III, born Alfonso de Borgia, was head of the Catholic Church and ruler of the Papal States from 8 April 1455 to his death. Borgia spent his early career as a professor of law at the University of Lleida; he later served as a diplomat for the kings of Aragon. He became a tutor for King Alfonso V's illegitimate son Ferdinand. After arranging a reconciliation between Alfonso and Pope Martin V, Borgia was made Bishop of Valencia. In 1444, Pope Eugene IV named him a cardinal, and Borgia became a member of the Roman Curia. During the Siege of Belgrade (1456), Callixtus initiated the custom that bells be rung at midday to remind the faithful to pray for the crusaders. The tradition of the Angelus noon bell still exists in most Catholic Churches to this day. He was also responsible for the retrial of Joan of Arc that saw her vindicated. He appointed two nephews as cardinals, one of whom became Pope Alexander VI.