Database: Abbasid Revolution
The Abbasids came to power following a revolution (747-750) during which family members descended from Prophet Muhammad's uncle al-Abbas led Arab dissenters, largely composed of troops from Iraqi and Khurasani regiments, against the Umayyad caliph in Damascus. Of particular import was the military leader Abu Muslim, a general of either Iraqi or Persian descent, whose prowess on the battlefield eventually led to the toppling of the reigning dynasty.
The Umayyad dynasty had been caliphs since 661. As a result of the rapid expansion of the empire in the ensuing years, tensions arose between local peoples and Umayyad administrators. In the 740s, the Umayyad empire was significantly challenged by North African peoples. The massive number of troops sent to these Western lands in a failed attempt to reassert caliphal authority in the region aided the Abbasid revolution in the East.
The notables of the Eastern empire who were unhappy with the reigning dynasty, specifically their tax policies, indeed took advantage of the weakened Umayyad military position to attack its Syrian heartlands, the powerbase of the dynasty. With fewer troops available, the Umayyad center of Damascus soon fell to Abu Muslim's troops after the Battle of the Zab (Iraq) in 750. After the victory, the newly installed Abbasid caliphs struggled with what to do with the dangerously popular hero of the revolution. Eventually, to secure his power, Caliph al-Mansur (r. 754-775) had the troublesome Abu Muslim assassinated. The Abbasid dynasty, however, continued to rely on its Persian power base, a fact reflected both in the move of the capital to a more Eastern city, Baghdad, as well as in the choice of the top administrators of the empire.