According to Byzantine juridical thought the state had two poles: the emperor (basileus) and the patriarch, the former exercising political power (potestas) and the latter ecclesiastical authority (auctoritas). The capture of Constantinople on 29 May 1453 by the Ottomans meant the end of the Byzantine state. But if the Byzantine emperor was no more, the ecumenical patriarchate survived, though only because the religion of the conqueror permitted its existence.

Byzantium had existed under the shadow of the Ottomans for more than half a century before its final fall. This produced a series of problems for the ecumenical patriarch, now that the majority of the metropolitan and episcopal sees in Thrace and the southern Balkans, which constituted the core of the patriarchate of Constantinople, came under Turkish domination, leaving Constantinople as an island in the middle of Ottoman territories. Nevertheless, representatives of the Greek Orthodox Church were present and active in these territories. This situation had its roots in the aftermath of the battle of Mantzikert (1071), when much of Asia Minor passed under the control of the Seljuq Turks. By the end of the fourteenth century the Seljuqs were a distant memory and the dominant Anatolian power was now the Ottomans, who had already conquered Thrace and much of the Balkans. Both Seljuqs and Ottomans applied the principles of the Koran, which recognizes the Peoples of the Book, that is, the Jews and the Christians. The Orthodox Church survived under the Seljuq sultans with metropolitans and bishops established in several Anatolian towns.