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 close villages. They worked in vast groups, without receiving regular wages, and their daily feed ration was made up only of flour, dates and hulled grain. Their chief, named Alī ibn Drivenḥammad, was a man who became aware of their misery and promised to them grounds and richnesses. While being presented in the form of a prophet, or mahdī, it managed to rejoin them and to involve them in an insurrection into 869. It succeeds in seizing Baṣruffle and of its surroundings, thus that of Ahwāz and Wāsiṭ by using a strategy of violence against its adversaries. It also profited from the support of certain Arab tribes of the area. 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. Because the important revolts are not nourished that of despair, they require for prospects to take form, to be formed and exist, even if their lifespan remains often transitory. This rebellion leaves the commun run of the servile revolts. It has an educated chief, a political project, a social horizon which combines the property and Freedom, the whole under the banner of the equality. Ali ibn Muhammad was not Zanj. It was Arab. It is made known like poet with Samarra, then like prophet in the area of Basra. Having failed in its attempts at preceding revolts, in Bahrain and Basra, it declares being a descendant of Ali and seeks to bind to the slaves. It undertakes to raise them and promises to them to improve their life, to return them in their main turns slaves and to give them beautiful residences. It converts them with the kharidjism, doctrines levelling which affirm that the caliphate must return to best from the Moslems, was it slave. Fanaticized, Zanj regard as inaccurate all the other Moslems. They undertake a fight to the death against these heretics who, in their eyes, merge with the great landowners. Their movement extends very quickly thanks to the rallying from the black troops from the imperial armies, to the adhesion of certain tribes Bedouins and the solidarity of the hostile peasants to the owners. Zanj inflict several defeats with the imperial army, seize important areas in Iraq and in Persia, occupy into 878, Wāsiṭ, an old garrison town, and threaten Basra, and even Baghdad. Ali ibn Muhammad created around the marshes his own state, striking a Zanj currency and establishes a capital, Muktarah, and establishes a diplomacy to try to be combined with the other dissenting movements of the Abbasids, like Saffarides, Quarmates and Toulounides. It will however fail in blood when the Abbasids manage to organize an army of great width, and will promise to the rebels and to the slaves, the safe life at the price of their treason. Ali ibn Muhammad will die during engagements.The revolt of Zanj was without mercy. It is a revolt which does not make prisoners. Thus, the bag of Basra was particularly cruel. More than 250.000 died according to Al-Tabari. What is sure, it is that Zanj, which carried out a war of guerrilla, benefitted from the geography of the marshes which they knew perfectly and of the weakness of the Abbasside capacity, weakened and occupied with other conflicts. Finally Freedom, the equality and the property conferred a capacity of attraction on its movement.