Mesopotamia (including among other cities Amida, Nisibis, Dara, and Edessa) was conquered and became a province of the Ottoman Empire.
This conquest led to designs on Syria and Egypt, a sufficient pretext being found in the alliance between the old Mamluk Sultan Kansuh Ghuri and the Shah Ismail. The Mamluk army awaited the invader at Aleppo; and Selim, here again conspicuously superior in artillery, won a victory which decided the fate of Syria (1516). The old Sultan's successor Tumanbeg was defeated in an equally disastrous battle at Reydaniya near Cairo (January, 1517). Thus Syria and Egypt were brought once more under the authority of the lords of Constantinople, to remain so actually or formally till the present day. The conquest of Egypt was followed by the submission of Arabia to the Sultan's sway.
The same year which saw the conquest of the Nile country witnessed an important exaltation of the dignity of the Ottoman ruler. The Ottoman princes had been originally Emirs under the Seljuks, and, even after they had become the strongest power of the Mohammadan world, though they might demean themselves as Caliphs, they had no legal claim to be considered its heads. It is one of the fundamental principles of Islam that all Muslims shall be governed by a single Imam, and that Imam must be a member of the Koreish, the tribe of the Prophet. At this time the Imamship was in the hands of a shadow, Mohammad Abu Jafar of the race of Hashim, who kept up the semblance of a court at Cairo. The last of the Caliphs of the Abbasid line, he resigned the caliphate to the Sultan Selim. This formal transference is the basis of the claims of the Sultans of Turkey to be the Imams or supreme rulers of Islam, though they have not a drop of Koreish blood in their veins. The translation of the Caliphate was confirmed by the recognition which Selim received at the same time from the Sherif of Mecca, who sent him the keys of the Kaaba, thus designating him as the protector of the Holy Places.
The Imam, according to the Ottoman code of Mohammadan law, has authority to watch over the maintenance of the laws and the execution of punishments; to defend the frontier and repress rebels; to raise armies and levy tribute; to celebrate public prayer on Fridays and in Bairam; to judge the people; to marry minors of both sexes who have no natural guardians; and to divide the spoils of war. He is thus supreme legislator and judge, the religious head of the State, the commander-in-chief, and he possesses absolute control of the finances. His ecumenical authority rests on a verse of the Koran: whoever dies without acknowledging the authority of the Imam of his day is dead in ignorance. The Imam must be visible to men; he cannot lurk in a cave like the Mahdi, for whose coming the heretical Shiites look. It is discreetly provided that the Imam need not be just or virtuous, or the most eminent man of his time; it is requisite only that he should be able to enforce the law, defend the frontiers, and sustain the oppressed.