The opportunity presented by European slave dealers became the major (though not the only) stimulus for a great deal of social violence between diffe… - Walter Rodney

No comprehensive studies have as yet been devoted to the role of Africans in the armies of the colonial powers in a variety of contexts. However, the indications are that such studies would reveal a pattern very similar to that discovered by historians who have looked at the role of black soldiers in the white-controlled armies of the U.S.A.; namely, that there was tremendous discrimination against black fighting men, even though black soldiers made great and unacknowledged contributions to important victories won by the white-officered armies of the U.S.A. and the colonial powers. Hints regarding discrimination are to be seen from regulations such as that barring African soldiers in the West African Regiment from wearing shoes and from the fact that there were actually race riots in the European campaigns, just as black troops fighting for the U.S.A. continued to riot right up to the Vietnam campaign.

The abandonment of traditional iron smelting in most parts of Africa is probably the most important instance of technological regression.

Slavery is useful for early accumulation of capital, but it is too rigid for industrial development. Slaves had to be given crude non-breakable tools which held back the capitalist development of agriculture and industry. That explains the fact that the northern portions of the U.S.A. gained far more industrial benefits from slavery than the South, which actually had slave institutions on its soil; and ultimately the stage was reached during the American Civil War when the Northern capitalists fought to end slavery within the boundaries of the U.S.A. so that the country as a whole could advance to a higher level of capitalism.