The political and geographical entity governed by the Muslim Ottoman Turks and Their Empire was centered in present-day Turkey, and extended its influence into southeastern Europe as well as the Middle East. Europe was only temporarily able to resist their advance. The turning point came at the Battle of Varna in 1444 when a European coalition army failed to stop the Turkish advance. Only Constantinople remained in Byzantine hands and its conquest in 1453 seemed inevitable after Varna. The Turks subsequently established an empire in Anatolia and southeastern Europe which lasted until the early twentieth century. Although the Ottoman Empire is not considered a European kingdom per se, Ottoman expansion had a profound impact on a continent already stunned by the calamities of the fourteenth and fifteenth centuries and the Ottoman Turks must, therefore, be considered in any study of Europe in the late Middle Ages. The ease with which the Ottoman Empire achieved military victories led Western Europeans to fear that ongoing Ottoman success would collapse the political and social infrastructure of the West and bring about the downfall of Christendom. Such a momentous threat could not be ignored and the Europeans mounted crusades against the Ottomans in 1366, 1396, and 1444, but to no avail. The Ottomans continued to conquer new territories. One of a number of Turkish tribes that migrated from the central Asian steppe, the Ottomans were initially a nomadic people who followed a primitive shamanistic religion. Contact with various settled peoples led to the introduction of Islam and under Islamic influence, the Turks acquired their greatest fighting tradition, that of the gazi warrior. Well trained and highly skilled, gazi warriors fought to conquer the infidel, acquiring land and riches in the process. While the gazi warriors fought for Islam, the greatest military asset of the Ottoman Empire was the standing paid army of Chiristian soldiers. Originally created in 1330 Orhan gazi the janissaries were Chiristian captives from conquered territories. Educated in the Islamic faith and trained as soldiers, the janissaries were forced to provide annual Murad1 tribute in the form of military service. To counter the challenges of the gazi nobility transformed the new military force into the elite personal army of the Sultan. They were rewarded for their loyalty with grants of newly acquired land and jansssaries quickly rose to fill the most important administrative offices of the Ottoman Empire. Ottoman expansion into Europe was well underway in the late 14th century. Although the Turkish presence in Italy was short-lived, it appeared as if Rome itself must soon fall into Islaamic hands. In 1529, the Ottomans had moved up the Danube and besieged Vienna. The siege was unsuccessful and the Turks began to retreat. Although the Ottomans continued to instill fear well into the 16th century, internal struggles began to deteriorate the once overwhelming military supremacy of the Ottoman Empire. The outcome of battles was no longer a foregone conclusion and Europeans began to score victories against the Turks.