In practice, the emperor had the upper hand over much of church administration, though strong patriarchs could occasionally play a decisive role in politics: Nicholas I (byname Nicholas Mystikos; patriarch 901–907, 912–925) and Polyeuctus (patriarch 956–970) excommunicated emperors for uncanonical acts.
In the area of faith and doctrine, the emperors could never impose their will when it contradicted the conscience of the church: this fact, shown in particular during the struggle over iconoclasm in the 8th and 9th centuries and during the numerous attempts at union with Rome during the late medieval period, proves that the notion of caesaropapism is not unreservedly applicable to Byzantium.
The Church of the Holy Wisdom, or Hagia Sophia, built by Justinian in the 6th century, was the centre of religious life in the Eastern Orthodox world.
It was by far the largest and most splendid religious edifice in all of Christendom.
Missionary expansion toward Asia and emigration toward the West, however, have helped to maintain the importance of Orthodoxy worldwide.metropolitans. The order of precedence in which the autocephalous churches are listed does not reflect their actual influence or numerical importance.