The Council of Basel first started as the 17th
ecumenical council of the
Roman Catholic Church. It was
convoked by
Pope Martin V shortly before his death in
1431, and the convocation was confirmed by his successor,
Pope Eugene IV.
The Council of Constance introduced the concept of concilar theory, the idea that the council had autority over the pope, and the Council of Basel would be the first real test. The council was convened to tackle two major issues. Disputes with the Hussites that had lead to the Hussite Wars, which Holy Roman Emperor Sigismund wanted resolved in order to reclaim his title as king of Bohemia, and the issue of union between the Eastern and Western churches.
It wasn't long before the council came into conflict with Pope Eugene IV. The pope attempted to dissolve the council, but was overruled. With Sigismund acting as mediator, a compromise was reached, but the council's repeated usurping of papal authority finally led to Eugene declaring the council heretical with his 1437 bull Doctoris gentium.
Not to be discouraged, the council continued as an anticouncil, even electing their own pope, Pope Felix V. However, eroding support for the council forced Felx to abdicate in 1449 and the council would soon recognize Eugene's successor Pope Nicholas V and dissolve itself.
Not that the council was without its accomplishments. A compromise was reached with the Hussites. Called The Compactata, it allowed Sigismund to finally claim the Bohemian throne. While it did little to address Hussite demands, it also legitimized the questioning of feudalism and the Roman Catholic Church, and would ultimately lead to the Protestant Reformation.