Ottoman Ethnarchy
When the Ottoman Turks conquered Constantinople in 1453, the Patriarchate ceased to function. The Patriarchate was restored by the conquering Islamic Ottoman ruler, Sultan Mehmed II, who wished to establish his dynasty as the direct heirs of the Eastern Roman Emperors, and who adopted the imperial title Kayser-i-Rûm "Caesar of Rome", one of his subsidiary titles but a most significant one. He bestowed the office of Patriarch in 1454 to the illustrious Byzantine scholar-monk George Scholarius, who was well known for his opposition to union with the Latin West, who took the name of Gennadius II.
The Patriarch was designated millet-bashi (ethnarch) of the Millet of Rum (Turkish for Rome, i.e. Byzantium), which included all Orthodox Christians under Ottoman rule, regardless of their nationality (ethnicity) in the modern sense. This role was carried out by ethnic Greeks at their great peril, in the midst of enormous difficulties and traps and inevitably with mixed success. Several incumbents of the patriarchal throne were summarily executed by the Ottoman authorities, most notably Patriarch Gregory V, who was lynched on Easter Monday 1821 as partial retribution for the outbreak of the last and only successful Greek Revolution.
In the 19th century, the rising tide of nationalism and secularism among the Balkan Christian nations led to the establishment of several autocephalous national churches, generally under autonomous Patriarchs or Archbishops, leaving the Ecumenical Patriarch only direct control over the ethnically Greek-originated Orthodox Christians of Turkey, parts of Greece and the archdioceses in North America, Asia, Africa and Oceania where growing Greek and other migrant communities have gradually constituted a significant orthodox diaspora. Turkish and Armenian Orthodox Christians in Turkey have independent Churches.
Read more about this topic: Ecumenical Patriarch Of Constantinople