Several historians such as British historian Edward Gibbon and the Greek historian Dimitri Kitsikis have argued that after the fall of Constantinople, the Ottoman state took over the machinery of the Byzantine (Roman) state and that in essence, the Ottoman Empire was a continuation of the Eastern Roman Empire under a thin Turkish Muslim 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 emphasised the Islamic character of the Ottoman state, seeing the Ottoman state as a "Jihad state" dedicated to expanding the Muslim world. Many historians led in 1937 by the Turkish historian Mehmet Fuat Köprülü championed the "Ghazi 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. They 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.