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.
Rise of the Ottoman Empire
In 1938 the Austrian historian Paul Wittek published an influential work entitled "The Rise of the Ottoman Empire", in which he put forth the argument that the early Ottoman state was constructed upon an ideology of Islamic holy war against non-Muslims. Such a war was known as "gaza", and a warrior fighting in it was called a "gazi". Wittek's formulation, subsequently known as the "Gaza Thesis," was influential for much of the twentieth century, and led historians to portray the early Ottomans as zealous religious warriors dedicated to the spread of Islam. Beginning in the 1980s, historians increasingly began to criticize Wittek's thesis. Scholars now recognize that the terms "gaza" and "gazi" did not have strictly religious connotations for the early Ottomans, and were often used in a secular sense to simply refer to raids. Additionally, the early Ottomans were neither strict orthodox Muslims nor were they unwilling to cooperate with non-Muslims, and several of the companions of the first Ottoman rulers were either non-Muslims or recent converts. The idea of holy war existed during the fourteenth century, but it was only one out of many factors influencing Ottoman behavior. It was only later, in the fifteenth century, that Ottoman writers retroactively began to portray the early Ottomans as zealous Islamic warriors, in order to provide a noble origin for their dynasty which had by then constructed an intercontinental Islamic empire.