Following the Turkish conquest of Constantinople in 1453, the Ottoman Sultan Mehmed II established the Millet System, according to which the different ethnic groups within Constantinople and the rest of the Ottoman Empire were to be governed by a group of institutions based on faith. For this purpose, Mehmed II also founded previously non-existent religious authorities such as the Armenian Patriarchate of Constantinople in 1461. Earlier, the Byzantines considered the Armenian Church as heretic and did not allow the Armenians to have churches inside the walls of Constantinople. Several Armenian saints, such as Saint Narses, were exiled and imprisoned in the Princes' Islands near Constantinople, in the Sea of Marmara. With the Millet System, a great deal of the internal affairs regarding these communities were assigned to the administration of these religious authorities; such as the Ecumenical Patriarchate for the affairs of all Orthodox Christians, the Armenian Patriarchate for the affairs of the Armenian (and for some time also the Syriac) Christians, and later the Chief Rabbi for the affairs of the Jews.