The Great Schism
When we are talking about the Great Schism, we can refer either to
the split between the Byzantine Church and the Roman Church that occurred in 1054 or to the Great Western Schism
that occurred between 1378 and 1417.
The Schism of 1054 (also
known as the East-West Schism) occurred when a representative of the Roman pope excommunicated the
patriarch of Constantinople, and the patriarch excommunicated the Roman pope in return.
That dual excommunication caused a formal split within the
Christian church, dividing it into the Eastern Orthodox Church based in Constantinople and the Western Catholic
Church based in Rome.
The Great Western Schism was the split in Latin Christendom that
occurred between 1378 and 1417.
From 1378 to 1409, there were two rival popes, one in Rome and
one in Avignon, France, and each claimed to be the one true pope.