With the election of Martin V as pope on Nov. 11, 1417, the Western Schism (1378-1417) finally came to an end

With the election of Martin V as pope on Nov. 11, 1417, the feast of St. Martin, the Great Western Schism (1378-1417) finally came to an end.

The Schism began with the election of Urban VI, one of the most unstable popes in all of papal history and the last non-cardinal to be elected to the papacy. So intransigent and unreasonable was Urban VI that the French cardinals, who had seen the last French pope elected with Gregory XI (1371-78), elected an antipope, Clement VII.

As the darker side of the new pope's personality had disclosed itself, the French cardinals asked Urban to abdicate, but he refused. Five days later, they sent out a notice to the Christian world that the pope had been deposed as incompetent.

The French cardinals moved to an Italian city, Fondi, where they elected the cousin of the French king, Cardinal Robert of Geneva on Sept. 20. As soon as he was crowned Oct. 31, the Great Western Schism erupted.

https://www.ncronline.org/blogs/essays-theology/end-western-schism