Baldassare Cossa,
c.1370–1419, Neapolitan churchman, antipope (1410–15; see
Great Schism ) with the name
John XXIII. He had a military career before entering the service
of the church. He was made a cardinal by Boniface IX (1402) and
proved himself able, especially in financial matters. In 1408 he
deserted Gregory XII and helped to bring about the Council of
Pisa to end the schism between the Roman and the Avignon popes.
The council, declaring both Gregory XII and Benedict XIII
deposed, set up a third claimant, Alexander V. On Alexander's
death a year later, Cardinal Cossa was elected. Of the three
rival “popes,” John had by far the greatest following. He
immediately sought the aid of Sigismund and helped elect
Sigismund Holy Roman emperor.
John allied himself with Louis II of Anjou (later king of
Naples) to make war on Lancelot of Naples and his ally Gregory
XII. An ineffective council at Rome (1412–13) was followed by
the Council of Constance which John convened under pressure from
Sigismund. At the opening of the council he reluctantly promised
(1415) to abdicate if his rivals would do so. Then,
surreptitiously, he fled to the lands of his ally Frederick of
Hapsburg. He was forced to return. The council formally deposed
him, and he submitted. He was held prisoner in Germany until
released by Martin V in 1418; he returned to Italy. He died
cardinal bishop of Tusculum. In his lifetime he had a reputation
for unscrupulousness and self-aggrandizement.
