Zanj were constrained African slaves to work with the clearing of the grounds in the south of Iraq. When they were raised, they were joined by the slaves of the cities and the villages. It also profited from the support of certain Arab tribes of the area. Their chief, named Alī ibn Muḥammad, was a man who became aware of their misery and promised to them grounds and richnesses. It managed to rejoin them and to involve them in an insurrection into 869. Al-Muwaffaq, brother and heir to the caliph, Al-Mutamid, managed to mobilize the army and undertook a series of military actions which ensured the victory over the Zanj rebels to him into 883.