Excerpts from Books and Wikipedia
"The schism in the Western Roman Church resulted from the return of the papacy to Rome under Gregory XI on January 17, 1377, ending the Avignon Papacy, which had developed a reputation for corruption that estranged major parts of Western Christendom. This reputation can be attributed to perceptions of predominant French influence and to the papal curia's efforts to extend its powers of patronage and increase its revenues. . . .The conflicts quickly escalated from a church problem to a diplomatic crisis that divided Europe. . . . A church council was held at Pisa in 1409 under the auspices of the cardinals to try solving the dispute. At the fifteenth session, 5 June 1409, the Council of Pisa attempted to depose both Pope and antipope as schismatical, heretical, perjured, and scandalous. But it then added to the problem by electing a second antipope, Alexander V. He reigned briefly from June 26, 1409, to his death in 1410, when he was succeeded by antipope John XXIII, who won some but not universal support." [Wikipedia]