He eliminated the corrupt power of the Omayyads in Damascus and initiated the dynasty of the Abbasids. Abbas safeguarded his victory by killing most of the surviving members of the Omyyad house.

The Omyyads had governed from Damascus, leaving Mecca only its religious predominance. The Abbasids founded a new city, Baghdad, from which to rule their territories. There remained only one province which refused to recognize the Abbasids, that was Spain. There, one of the few Omayyads to survive founded an independent state in 756.