Today in the Middle Ages: July 16, 1054

On July 16, 1054, the Pope excommunicated Michael Cerularius, Patriarch of Constantinople, setting in motion the events which would divide the Eastern Orthodox from the Roman Church.

Cerularius was excommunicated for refusing to alter centuries-old practices of the Eastern Church. He quarreled with papal representatives who then carried out the excommunication, and he in turn excommunicated them. Pope Paul VI and Patriarch Athenagoras jointly rescinded the excommunications in 1965 when they met at the Second Vatican Council, where many aspects of Roman Catholic practice were liberalized.