Book excerpt: By 735 an Arab empire stretched from Arles and Avignon in southern France to the Indus River and Central Asia, and a vital young civilization fostered by a new world religion was taking root. Yet the Muslim conquerors were divided by tribal quarrels, tensions among new converts, and religious revolts. In 745 a vigorous new successor to the Prophet took control in Damascus and began to restore the waning power of the Umayyad dynasty. Marwan II's attempts were thwarted, however, by revolts on every hand, even among his own relatives. The main body of dissidents was a well-trained group of revolutionaries in Khurasan, led by the remarkable Abu Muslim. By 748 they had seized control of the province and drive the governor, Nasr b. Sayyar al-Laythi, to his death and were advancing westward. This volume tells of the end of the Umayyad caliphate, the Abbasid Revolution, and the establishment of the new dynasty.