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*In 1378 the College of Cardinals elected Urban VI Pope, but a large number repudiated him five months later and elected Clement VII. Nations took sides, positions became entrenched, no one knew who was rightful Pope. To break the deadlock, cardinals from both camps convened on their own (hence invalidly) in 1409, "deposed" both Popes and elected a third, who died within a year, was succeeded by Balthazar Cardinal Cossa, who called himself John XXIII. Neither "deposed" Pope recognized the new one. Four years later, the Council of Constance met, made itself valid by having Urban's successor, Gregory XII, convene it and immediately abdicate. Thereupon the council deposed the other two Popes and started things off on the right foot again with Martin V (1417-31).