Ottoman Empire
Several historians such as British historian Edward Gibbon and the Greek historian Dimitri Kitzikis have argued that after the fall of Constantinople, the Ottoman state took over the machinery of the Roman state, and that in essence the Ottoman Empire was a continuation of the Eastern Roman Empire under a thin Turkish Islamic guise. Kitzikis called the Ottoman state "a Greek-Turkish condominium". The American historian Speros Vryonis wrote that the Ottoman state was centered on "a Byzantine-Balkan base with a veneer of the Turkish language and the Islamic religion". Other historians have followed the lead of the Austrian historian Paul Wittek who emphasized the Islamic character of the Ottoman state, seeing the Ottoman state as a "Jihad state" dedicated to expanding the world of Islam. Another group of historians led by the Turkish historian M. Fuat Koprulu championed the ""gazi" thesis" that saw the Ottoman state as a continuation of the way of life of the nomadic Turkic tribes who had come from East Asia to Anatolia via Central Asia and the Middle East on a much larger scale, and argued that the most important cultural influences on the Ottoman state came from Persia. More recently, the American historian Heath Lowry called the Ottoman state a "predatory confederacy" led in equal parts by Turks and Greeks converted to Islam.
Ottoman Empire
The Ottoman Empire, or as a dynastic institution, the House of Osman, was unprecedented and unequaled in the Islamic world for its size and duration. In Europe, only the House of Habsburg had a similarly unbroken line of sovereigns (kings/emperors) from the same family who ruled for so long, and during the same period, between the late 13th and early 20th centuries. The Ottoman dynasty was Turkish in origin. On eleven occasions, the sultan was deposed (replaced by another sultan of the Ottoman dynasty, who were either the former sultan's brother, son or nephew) because he was perceived by his enemies as a threat to the state. There were only two attempts in Ottoman history to unseat the ruling Ottoman dynasty, both failures, which suggests a political system that for an extended period was able to manage its revolutions without unnecessary instability. As such, the last Ottoman sultan Mehmed VI (r. 1918–1922) was a direct patrilineal (male-line) descendant of the first Ottoman sultan Osman I (d. 1323/4), which was unparallelled in both Europe (e.g. the male line of the House of Habsburg became extinct in 1740) and in the Islamic world. The primary purpose of the Imperial Harem was to ensure the birth of male heirs to the Ottoman throne and secure the continuation of the direct patrilineal (male-line) descendance of the Ottoman sultans.