in Roman Catholic church history, a council convened in 1409 with the intention of ending the Western (Western Schism) (or Great) Schism, during which rival popes, each with his own Curia (bureaucracy), were set up in Rome and Avignon. This meeting, which was the result of concerted action by cardinals of both obediences, was well attended. It deposed the two existing pontiffs, who refused to cooperate, and elected a third, Alexander V (Alexander (V)). Western Christendom was therefore divided into three parties until the Council of Constance (1414–18), which forced the three contending popes to resign and elected Oddone Colonna, a Pisan cardinal, as Pope Martin V. The Council of Pisa has never been regarded as valid by canonists or theologians.