3/4th of the European population were slaves under the Mongol Hordes 1200AD-1500AD who re-mapped the entire ethic makeup into Euro-Mongol half-breeds like my family who came emigrated from Poland to Cleveland 100 years ago.
Slavery was introduced to Africa by the Pope and the Catholic Church who commissioned the explorers of Portugal and Spain.
Truman re-introduced U.S. Slavery to Palestine in the 1940s by capturing and imprisoning Arab Christians and Arab Muslims and giving their land to Holocaust surviving Jews. There's some 6 Million slaves still held by the US puppet occupation regime in Palestine.