The taking of prisoners as slaves from enemy tribes and conquered peoples existed among the West Africans, and for that matter among ancient Europeans (Greeks and Romans) and Native Americans, from time immemorial. In the late 1600's English peasants who supported the failed insurrection of the Duke of Monmouth against King James II were condemned to slavery and shipped off to the Caribbean en masse to cut sugar cane on English plantations. But the industrial scale business of supplying tens of thousands of African slaves to Portuguese, Spanish, and British colonies in the New World was organized and overseen by Arabs.
This is not to discount the shameful participation of Christian Europeans, but ignoring or discounting the responsibility of muslims is like overlooking the role drug kingpins play in supplying crack in favor of condemning only the street corner vendors.
And the mooselimb participation in African slavery continues to this very day.....