Most people do not know the complete story of slavery. The half story of slavery is the evil white man on a wooden ship on the west coast of Africa. The whole story includes the fact that all of the slaves sent to the Americas were sold by Muslim slave wholesalers. Political Islam has a complete doctrine of slavery.
Mohammed was involved in every aspect of slavery. He captured slaves, received them as gifts, and owned slaves of all races. Only Kafirs could be enslaved.
Historically, all nations used slaves. The reason for the ending of slavery was that we built better slaves with engines and machinery, not our moral superiority.
John Azumah: The Legacy of Arab-Islam in Africa