The French cardinals return with their “antipope” to Avignon, thereby initiating the so-called Western Schism or Papal Schism (also known as the Great Schism of Western Christianity).

Clement's supporters include Queen Joan I of Naples and forty-seven-year-old Spanish churchman Pedro de Luna, who had been appointed cardinal in 1375 by Pope Gregory XI and had participated in the controversial conclave that had elected Gregory's successor.

Western, or Roman, Catholics have continuously debated the convoking and authority of councils.

Although all the bishops and theologians agree that the pope should have special prerogatives, reformers, who have for centuries claimed that protesters can appeal their grievances from the pope to a council, have formulated a theory of conciliarism: the idea that a council is ultimately above the pope.

The Western Schism in 1378 brings this debate to a head, since there are now two (and will later be three) popes.

Spanish cardinal Pedro de Luna, elected at the death of Antipope Clement VII of the Avignon line in 1394, swears that as Pope Benedict XIII to work toward reunification of the Roman and Avignonese obediences.

Vincent Ferrer, a forty-four-year-old Spanish Dominican protégé and friend of the new antipope, becomes his confessor.

The Roman College of Cardinals had chosen Pedro Martínez de Luna as Pope on the death of Urban VI in 1389; his election had therefore perpetuated the Western Schism.

At the start of his term of office, de Luna had been recognized as pope by the kingdoms of France, Scotland, Sicily, Castile, Aragon, Navarre, and Portugal.

As Benedict XIII, he had in 1396 sent Sanchez Muñoz, one of the most loyal members of the Avignon curia, as an envoy to the Bishop of Valencia to bolster support for the Avignon papacy in Spain.

However, in 1398 the French church withdraws their allegiance from the Avignon papacy.

Benedict is abandoned by seventeen of his cardinals, with only five remaining faithful to him.

An army led by Geoffrey Boucicaut, brother of the illustrious marshal of France, Jean le Maingre, occupies Avignon and initiates a five-year siege of the papal palace.

The antipope Benedict, besieged in his palace for the past five years, had managed to escape from Avignon on March 12, 1403 and seek shelter in territory belonging to Louis II of Anjou.

By this stage, Benedict's authority is no longer recognized in France, Portugal and Navarre, but he is acknowledged as pope in Scotland, Sicily, Castile, and Aragon, where Benedict flees to the protection of Martin I.

The Romans, the rioting having been suppressed by 1406, once again acknowledge Papal temporal authority, and Innocent feels able to return. (In March, Innocent VII makes Ludovico a marchese and conte di Fermo.)

But Ladislas, not content with the former concessions, desires to extend his authority in Rome and the Papal States.

To attain his end, he had aided the Ghibelline faction in Rome in their revolutionary attempts in 1405, but a squad of troops that King Ladislas had sent to the aid of the Colonna faction is still occupying the Castle of Sant' Angelo, ostensibly protecting the Vatican but making frequent sorties upon Rome and the neighboring territory.

Only after Ladislas is excommunicated does he yield to the demands of the Pope and withdraw his troops.

Innocent dies so suddenly at Rome, on November 6, 1406, that there are rumors of foul play, which have been denied ever since: there is no evidence for the truth of the allegation that his death was not due to natural causes.

His successor is Angelo Correr, chosen as Pope Gregory XII by a conclave consisting of only fifteen cardinals under the express condition that, should antipope Benedict XIII, the rival Pope at Avignon, renounce all claim to the Papacy, he also would renounce his, so that a fresh election might be made and the Western Schism could be ended.

The newly elected Roman pope, Gregory XII, starts negotiations with the antipope Benedict after the death of the Roman Pope Innocent VII in 1406, suggesting that they both resign so a new pope can be elected to reunite the Catholic Church.

The two rival pontiffs open wary negotiations to meet on neutral turf at Savona in Liguria, but soon begin to waver in their resolve.

Gregory’s Corraro relatives and Ladislas of Naples, the supporter of Gregory and his predecessor for political reasons, use all their influence to prevent the meeting, and each Pope is fearful of being captured by the party of the rival Pope.

The cardinals of Gregory openly show their dissatisfaction at his procedure and give signs of their intention to abandon him.

King Ladislaus of Naples besieges Ostia in 1408 to prevent a success of the French party in the schism between Gregory XII and Antipope Benedict XIII.

After a short siege, he captures the city by bribing the Papal commander, Paolo Orsini, and …

…enters Rome on April 25.

Later, …

…Perugia also falls into Ladislaus’s hands.