Answer:
The Byzantine split with Roman Catholicism came about when Pope Leo III crowned Charlemagne, King of the Franks, as Holy Roman Emperor in 800. From the Byzantine viewpoint, this was a slap to the Eastern Emperor and the Byzantine Empire itself — an empire that had withstood barbarian invasions and upheld the faith for centuries.
Step-by-step explanation:
In the end, Pope Leo and Patriarch Michael excommunicated each other and their respective churches. But more than 900 years later, in 1965, Pope Paul VI and Patriarch Athenagoras I of Constantinople removed the mutual excommunications.