Zanj rebellion, (AD 869–883), a black-slave revolt against the ʿAbbāsid caliphal empire. A number of Basran landowners had brought several thousand East African blacks (Zanj) into southern Iraq to drain the salt marshes east of Basra. The landowners subjected the Zanj, who generally spoke no Arabic, to heavy slave labour and provided them with only minimal subsistence. In September 869, ʿAlī ibn Muḥammad, a Persian claiming descent from ʿAlī, the fourth caliph, and Fāṭimah, Muḥammad’s daughter, gained the support of several slave-work crews—which could number from 500 to 5,000 men—by pointing out the injustice of their social position and promising them freedom and wealth. ʿAlī’s offers became even more attractive with his subsequent adoption of a Khārijite religious stance: anyone, even a black slave, could be elected caliph, and all non-Khārijites were infidels threatened by a holy war.