July 16, 1054, Patriarch of Constantinople Michael Cerularius was excommunicated, starting the “Great Schism” that created the two largest denominations in Christianity (the Roman Catholic and Eastern Orthodox faiths).
There were many key factors that added to the Great Schism such as...
the eastern and western churches spoke different languages.
the separation of the Roman Empire into two empires features prominently,
the immediate reason for the division of the church was that the patriarch of Constantinople and the patriarch of Rome decided to excommunicate one another.
