Khorasan. He subsequently directed the Abbasid advance across the Iranian plateau and into the Levant, culminating in the collapse of Umayyad authority and the proclamation of the Abbasid Caliphate. Thereafter he served as governor of Khorasan and emerged as one of the most powerful figures of the early Abbasid state.

Abu Muslim's growing prominence provoked concern within the Abbasid leadership. While the first caliph refrained from acting against him, the second