The Great Schism
The Great Schism was a period in European history between 1378 and 1417 during which two and sometimes three people claimed to be the legitimate pope. The Great Schism began after several cardinals argued that the election of Pope Urban VI in 1378 had been coerced by a hostile mob in Rome. The cardinals subsequently elected a different, competing pope, Clement VII. Different rulers in Europe supported one of the two popes, usually due to political expediency more than religious sentiment or legal arguments. The Great Schism eventually ended with the election of a single pope, Martin V, in 1417; however, the power of the papacy was dealt an irrevocable blow.
Maxson, Brian Jeffrey. 2018. The Great Schism. Encyclopedia of Diplomacy. Wiley-Blackwell. https://doi.org/10.1002/9781118885154.dipl0111 ISBN: 9781118885154