The Byzantine Empire was ultimately influenced by Catholicism. This empire had a high level of political, economic, and cultural life. The empire followed many Roman patterns and spread Orthodox Christianity throughout most of eastern Europe. Two separate civilizations formed by the two Christian influences, Catholic Christianity and Orthodox Christianity.
Historians generally refer to the Eastern Roman Empire after 476 as the Byzantine Empire. But this is an arbitrary distinction invented for the convenience of historians. People in the Byzantine Empire continued to think of themselves as Romans, and their empire as the Roman Empire, for centuries after 476. The Byzantine Empire would endure as a Christian empire for another 1000 years until it was finally overrun by the Ottomans in 1453.
In the Middle East and North Africa, the once powerful civilizations of Byzantium and the Abbasids had crumbled. The Byzantine Empire was pressed by Ottoman Turks; Constantinople fell in 1453. The Abbasids were destroyed by the Mongols in 1258.