Pope Gregory XII died on this day 605 years ago, aged ~90.
Gregory was born as Angelo Corraro, and was appointed as the bishop of Castello in 1380. In 1405, he was anointed as a cardinal by Pope Innocent VII.
Innocent died the following year, and Corraro was elected to succeed him. At this point in time, there was a schism within the Catholic Church between him and Antipope Benedict XIII. Gregory decided to get Benedict to relinquish his claim to the papacy, and in turn would resign. Gregory's relatives, as well as king Ladislaus of Naples, tried to prevent the meeting due to political reasons.
In 1414, Gregory initiated the ecumenical Council of Constance, and in July of 1415, he resigned as pope in an attempt to end the schism, and the council dismissed another claimant to the papacy, Antipope John XXIII, to complete it. The next pope, Martin V, would not be elected until November of 1417.
Gregory was the most recent pope to resign until Benedict XVI did so in 2013.