The image of the slave trade is a white slaver capturing African tribesmen, packing them like corkwood into a ship, selling them in the Antebellum South, and having a plantation owner work them to death. All of this took place on a scale of millions in the African slave trade to the New World.
But such massive levels of slavery did not begin with European discovery of the New World. In the Middle Ages, Vikings went on numerous slave raids of England and Eastern Europe, selling those capture on Volga slave markets. Most of all, Arab slave traders purchased millions of Africans and sent them to the Middle East to work on cotton and sugar cane plantations in Iraq.
Middle Eastern intellectuals argued that Africans were at a lower mental level than Arabs and thus of a suitable condition to be enslaved (to be fair, they thought the same of Scandinavians). Slaves were humiliated at markets in Cairo where they were stripped naked to be examined by potential buyers. And Africans were taken from their homeland where they would be shipped East to Cairo, Syria, Iraq, India, and even all the way out to Indonesia.
Find out how slavery is much older than we think but sadly universally cruel.