In 869, slaves, mostly of African origin, revolted in Southern Iraq against their masters, living mainly in the city of Basra, and against the Abbasid caliphate. The slaves, referred to as Zanj in the sources, rebelled due to the harsh conditions under which they lived. They worked on large plantations where they were primarily employed in reclaiming land by removing the nitrous topsoil to make it arable. They toiled under terrible working conditions, received little sustenance, and suffered cruel and harsh treatment at the hands of their overseers.
The rebellion was incited and led by Ali ibn Muhammad, a mysterious charismatic leader who was neither a slave nor a native of the marshy regions where he launched the movement that would cause the central authorities so much trouble for a period of 15 years. Ali ibn Muhammad and his band of followers attacked the plantations where the slaves worked and freed thousands of them. He promised the slaves that he would lead them to victory, wealth, and power. He also promised that he would treat them with respect and dignity and that he would never betray them.
Ali ibn Muhammad and his followers established a polity in Southern Iraq and the region of Ahwaz (in Southwestern Iran). They constructed their capital, al-Mukhtara, deep in the marshes. The rebels utilized the marshes to conduct a guerilla war against their enemies. They defeated several armies sent by the local authorities in Basra and drove back caliphal forces sent to subdue them from Samarra and Baghdad. The Zanj were only crushed when the caliphate focused a considerable amount of its military and resources on subduing the revolt, eventually pushing the rebels back to their capital. Even after the rebel capital was besieged, it took the caliphal armies 2 years to capture al-Mukhtara.
The rebellion took a heavy toll on the caliphate. The damage done to the economy, agriculture, and trade was devastating. Thousands lost their lives, irrigation systems were destroyed, and countless villages were abandoned. Even major cities such as Basra and Wasit were taken and sacked by the rebels, leaving much of the region devastated and depopulated. The caliphate suffered from losses of revenue and prestige and became further fragmented with regional dynasties and a rival caliphate rising to control much of its territory, leaving the Abbasid caliphs with little actual power beyond the capital.
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