Some quotes:
"If you draw boundaries differently--to surround, say, all African equatorial rain forest land rich in wild rubber--then what happened in the Congo is, unfortunately, no worse than what happened in neighbouring colonies: Leopold simply had far more of the rubber territory than anyone else. Within a decade of his head start, similar forced labor systems for extracting rubber were in place in the French territories west and north of the Congo River, in Portuguese-ruled Angola, and in the nearby Cameroons under the Germans..."
"...In France's equatorial African territories, where the region's history is best documented, the amount of rubber-bearing land was far less than what Leopold controlled, but the rape was just as brutal. Almost all exploitable land was divided among concession companies. Forced labor, hostages, slave chains, starving porters, burned villages, paramilitary company "sentries", and the chicotte were the order of the day. Thousands of refugees who had fled across the Congo River to escape Leopold's regime eventually fled back to escape the French. The population loss in the rubber-rich equatorial rain forest owned by France is estimated, just as in Leopold's Congo at roughtly 50%. And, as in Leopold's colony, both the French territories and the German Cameroons were wracked by the long, fierce rebellions against the rubber regime."
"The French scholar Catherine Coquery-Vidrovitch has published a chilling graph showing how, at one French Congo post, Salanga, between 1904 and 1907 the month-by-month rise and fall in rubber production correlated almost exactly to the rise and fall in the number of bullets used up by company "sentries"--nearly four hundred in a busy month."
"...During this period a scandal erupted in France when two white men were put on trial for a particularly gruesomse set of murders in the French Congo; to celebrate Bastille Day, one had exploded a stick of dynamite in a black prisoner's rectum..."
"...In the 1920s, construction of a new railway through French territory bypassing the Congo River rapids cost the lives of an estimated twenty thousand forced laborers, far more than had died building and later rebuilding Leopold's railway nearby."
It may assuage Western consciences to blame the horrific crimes of the Congo on a single man, but the reality was that, if it was profitable to do, European colonialism was willing to embrace slavery and mass murder across occupying powers. And this was not just from the rulers either: horrendous brutality came from soldiers, administrators and merchants on the ground also. It is the nature of a colonial system where one group of people have absolute power over another, and where they see them as racially inferior semi-beasts.
Joseph Conrad put it well: "All Europe contributed to the making of Kurtz".