In the seventh century the Byzantine Empire lost all of North Africa and much of the Middle East to the Muslim Arabs. Over the next eight centuries Byzantium and Muslim states in the Middle East confronted each other, and despite periods of peaceful coexistence and trade the Byzantines steadily lost the rest of their territories to Muslims. Beginning in the eleventh century Muslim Turks of Central Asian origin invaded Byzantine Anatolia, conquered it, and transformed it from a Christian, Greek-speaking land to a Muslim, Turkish-speaking territory. One of the Turkish states in northwestern Anatolia-the Ottoman principality ruled by the family of Osman-then sent its armies into Europe and began a systematic conquest of the Byzantine lands in the Balkans. By 1450 virtually nothing was left of the Byzantine Empire but its capital. Although the city had withstood many Muslim sieges, beginning with the early Arab attacks in the 670s, it was now more vulnerable than ever. The Ottomans had long coveted this great prize and the stature of a universal empire that it would confer upon them. In 1452, after considerable debate among his advisers, Sultan Mehmed II began preparations for the decisive assault on the city.