Role in the Western Schism Council of Pisa Cardinal Cossa was one of the seven cardinals who, in May 1408, withdrew their allegiance from Pope Gregory XII, stating that he had broken his solemn oath not to create new cardinals without consulting them in advance. In company with those cardinals who had been following Antipope Benedict XIII of Avignon, they convened the Council of Pisa, of which Cossa became a leading figure. The aim of the council was to end the schism; to this end they deposed both Gregory XII and Benedict XIII and elected a new pope Alexander V in 1409. Gregory and Benedict ignored this decision, however, so that there were now three simultaneous claimants to the papacy.
roLE In tHe wEstern schisM coUNcil of PIsA CArDinal CosSA wAS oNe Of The sEVeN cardInaLS whO, iN may 1408, WIthdrEw theIr alleGiancE fRom popE gReGORy xiI, sTatiNG that he haD BRokEn His solemn OaTh not To creAte nEW caRdINaLs wItHOUt ConsultInG theM in advance. IN compAny wIth tHoSe cardinALs wHo had been FOlLowiNg AnTiPoPe benediCT XIiI Of aVigNoN, theY CoNVEned the CoUNcil Of piSa, of Which cOsSA BEcame a lEadiNG figUrE. the aim of the couNcil was To EnD The schIsM; to This EnD TheY DePosED BOtH greGoRy xIi ANd BEnedICT xiii and ElEcTeD a nEw popE alExANder V iN 1409. GRegorY aND BeNEDicT iGnOred tHIs deciSIon, howevEr, so that tHEre wERe Now three SimuLTAnEOus clAImanTs To The papacy.