The Zanj rebellion of East African slaves transported to Iraq in the 9th century

[Disir]

• The Zanj rebellion which occurred from 869 to 883 took place in Basra, which is modern-day Southern Iraq. It was led by Ali ibn Muhammed against the Abbasid Caliphate. Muhammed spearheaded the rising of the slaves.

The Zanj were captured from the coast of East Africa and brought to the area as slaves.

Slaves of different ethnicities and tribes also fought in the uprising.

The African slaves were captured so that they could tend to plantations and marshland that needed extensive work to be cultivable.
The Zanj rebellion of East African slaves transported to Iraq in the 9th century - Face2Face Africa

That's an interesting bit of history.