State church
A number of disagreements over matters of Ecclesiology developed slowly between the Western and Eastern wings of the State church of the Roman Empire centred upon the cities of Rome (considered to have "fallen" in 476) and New Rome/Constantinople (also considered to have "fallen" in 1453) respectively. The disputes were a major factor in the formal East-West Schism between Pope Leo IX and Patriarch Michael I in 1054 and are largely still unresolved between the churches today.