Abbasid Revolution

Opposition to the Umayyads had many sources: the grievances of non-Arab converts (mawali), still treated as second-class Muslims, the feuds of Arab tribal factions, and the hope of many that a ruler from the family of Muhammad would restore justice — a hope kept alive by the memory of Husayn’s death at Karbala. The descendants of the Prophet’s uncle al-Abbas claimed that Abu Hashim, a grandson of Ali, had passed his rights to their family before his death in 716 or 717 — a story historians regard as a fabrication — and so took over the Hashimiyya, a Shi'ite sect that had grown out of the followers of al-Mukhtar. According to later accounts, from the late 710s their missionaries worked in secret in Khorasan, calling for ‘a member of the House of the Prophet acceptable to all’ without naming him. In the 740s, while the caliphate was torn by the Berber revolt, the Umayyad civil war of 744–747 (the Third Fitna) and Kharijite risings, the imam Ibrahim sent his freedman Abu Muslim to lead the movement there.

On 9 June 747 the black banners were raised in the villages around Merv. In February 748 Abu Muslim took Merv, and his general Qahtaba ibn Shabib drove the Umayyad governor Nasr ibn Sayyar westwards, winning battles at Gorgan (748), near Isfahan (749) and at Nahavand. In the late summer of 749 the Khorasani army crossed the Euphrates; Qahtaba fell, but his son al-Hasan entered Kufa on 2 September. After weeks of hesitation by Abu Salama, the movement’s leader in Kufa, who seems to have wanted an Alid caliph, Abu al-Abbas — brother of the imam Ibrahim, who had died in Umayyad captivity at Harran — was acknowledged as caliph in the mosque of Kufa on 28 November 749. On 25 January 750 an army under his uncle Abd Allah ibn Ali routed Marwan II on the Great Zab, a tributary of the Tigris. Damascus fell in April; Marwan fled to Egypt, where he was killed in August 750.

The victors hunted down and killed most members of the Umayyad house; one of the few to escape, Hisham’s grandson Abd al-Rahman, later founded an Umayyad emirate in al-Andalus. The Abbasids soon turned on their own allies — Abu Salama was killed in 750 and Abu Muslim in 755 — and disappointed the Alid hopes that had helped them to power. Yet the revolution ended the privileged position of the Arab tribal aristocracy: converts of every origin became full members of the community, government passed to a bureaucracy that borrowed Sasanian models, and the capital moved to Iraq, where al-Mansur founded Baghdad. Almost everything known about the revolution comes from sources written under the Abbasids more than a century later, and historians still debate the respective roles of Arab settlers and Iranian converts in Khorasan.