Where was the center of the Eastern Orthodox Church?

Constantinople

Explanation:

Hope this helps:)

between Rome and Constantinople

the conditions that made the byzantine empire vulnerable to attacks by the muslin turks were the sack of constantinople by western crusaders, the conquests of the sultanate of rum, presence of rival kingdoms and finally the set up of fiefdoms at the empire which were owned by the ghazis (turkish warriors).

during world war ii