The Islamic empire arose spectacularly in the 7th century and exercised influence over a large geographic area until its fall to Mongol invaders in the 13th century. The rulers, called caliphs, ushered in a new Islamic civilization with customs and practices both distinct from and partially influenced by those of the areas it conquered. The reigns of these caliphates, including the Abbasid caliphate, which presided at the time of the Islamic Golden...