In the Middle East, during these centuries, the ‘Abbasids, after their victory over the Umayyads, had transformed the Umayyads’ Arab empire into a multinational Muslim empire. They moved the capital of the empire from Syria to Iraq, where they built a new capital, Baghdad, from which, during the next five centuries, they would influence many of the main events of Islamic history. In the early period of ‘Abbasid rule,...