The emergence of the Islamic state, seventh century
Arab peoples conquered the Sassanid empire and part of Byzantium
Prolonged sieges of Constantinople by Islamic armies
Byzantium survived partly because of Greek fire
Byzantine society reorganized
Provinces ( themes ) under generals
Armies of free peasants helped agricultural economy
I. Byzantium and western Europe: ecclesiastical and political tensions
The Iconoclastic Controversy of 710AD completed the break between Rome and Constantinople.
Facing numerous defections to the Muslims along his southern border, and the creation of a Muslim Persia along his eastern border, Emperor Leo initiated religious reforms in an attempt to retain followers.
The main item was a declaration that religious images were corrupt . This appealed to Eastern Monophysites and to Muslims who distrusted the worship of anything that came between the individual and the deity (saints), but it also resulted in the destruction of much Byzantine religious art.
Reforms had political goals as well as spiritual goals.
By purifying Christianity, they hoped to reduce the attractiveness of Islam to Eastern Monophysites and other religious opponents.
By eliminating religious images, they hoped to undermine the worship of saints, including that of St. Peter, who was the ancestral founder of the Roman bishopric.
Finally, by doing away with the worship of saints, the emperor also found a reason to close monasteries and confiscate their wealth for the Empire.