A slave rebellion is an armed uprising by slaves. Slave rebellions have occurred in nearly all societies that practice slavery, and are amongst the most feared events for slaveholders. The most successful slave rebellion in history was the 18th-century Haitian Revolution led by Toussaint L'Ouverture against their French colonial rulers, and which founded the extant country. Other famous historic slave rebellions have been led by the Roman slave Spartacus, as well as the thrall (Scandinavian slave) Tunni who rebelled against the Swedish monarch Ongentheow, a rebellion that needed Danish assistance to be quelled. In the ninth century, the poet-prophet Ali bin Muhammad led imported East African slaves in Iraq during the Zanj Rebellion against the Abbasid Caliphate; Nanny of the Maroons was an 18th-century leader who rebelled against the British in Jamaica; and the Quilombos dos Palmares of Brazil flourished under Ganazumba (Ganga Zumba). The 1811 German Coast Uprising in the Territory of [New] Orleans was the largest rebellion in the continental U.S.; Denmark Vesey rebelled in South Carolina, USA; and Madison Washington during the Creole case in 19th century United States.