In 1406 an aged Italian cardinal named Angelo Correr (ca. 1327-1417) was elected pope; calling himself Gregory XII, he had a bedeviled nine-year tenure as head of the Roman Catholic Church. His ascension to the Holy See came during a tumultuous crisis in Christian Europe usually referred to as the Great Schism, a conflict that divided clerics, royals, and the faithful for several decades. At one period of Gregory XII's rule, there were two other popes elsewhere vying for authority, but his own eventual assent to a compromise helped end the Schism.

Very little is known about the life of Angelo Correr, the man who would later take the name Gregory XII. Sources place his date of birth around 1327, and it is known that his family was among Venice's wealthy and influential clans. At the time, the lagoon city on the Adriatic Sea was a powerful sovereignty that controlled...