The Great Western Schism was a division within the western world. It began with the election of pope Urban VI, an Italian who had an even temperament, but his temper did not stay the same after his election.
Urban suddenly began having erratic behaviors , even striking other church officials. The college of cardinals couldn’t understand what was wrong with him, as they saw he wasn’t getting any better they decided it best to elect a different pope- pope Clement VII from France. Their excuse for the change of pope was that they were under pressure when choosing Urban as a mob was outside threatening them. Urban in turn refused to resign and continued to act as pope in Rome, driving the college of cardinals to move back to Avignon where Clement was to remain as pope.
After the deaths of each pope each of their cardinal groups elected another pope, leading to another two popes. Something had to be done. The people then resolved to hold an ecumenical council, the Council of Pisa in 1409, where they elected yet another pope ending up with three popes who didn’t care to resign. Another council was held, the Council of Constance in 1414. There it was resolved that all three popes had to resign. Finally pope Martin V was elected and considered a legitimate pope. Later in the twentieth century the church finally determined that the popes in Rome were really the correct ones.