"There is no God but God"

Islam was preached in the early decades of the seventh century by Muhammad, who received divine revelations collected in a scripture called the Qur'an. Islam was the faith of what became a vast empire that included much of the ancient Christian world, from Persia through North Africa to Spain. For much subsequent history, both the Byzantine Empire and western Christendom have been locked in uneasy relationships with the Islamic world, in which creative interaction was frequently overshadowed by violence. Violent episodes include the Crusades (1095-1291), the fall of Constantinople to the Ottoman Turks (1453), the reconquest of Spain (completed in 1492), and the Ottoman advances into Europe of the fifteenth and sixteenth centuries.