The Congo was a perfect colony for Leopold II for several reasons. First, ivory and rubber were plentiful and could be systematically gathered and shipped to Europe. Second, the only law there was Leopold's: Although he constantly presented himself to his European contemporaries as a philanthropist and humanitarian, Leopold ran the Congo (without ever visiting it) from a distance with an iron hand. Third, labor was plentiful and, more important to Leopold, free, because his agents routinely forced the Congolese into slave labor by means of torture or intimidation: Women, for example, were often kidnapped and held until their husbands and sons gathered sufficient quantities of rubber. Forth, there were few operating expenses: Huts and mess-halls were constructed for the agents, and the construction of a railroad system running through the Congo guaranteed that supplies could reach different stations quickly. Finally, the colony was thousands of miles away from sheltered European skies. People could not condemn what they could not see.
Leopold's agents, therefore, comprised a chaotic, unforgiving, and hateful force determined only to make the most money possible by exploiting the natives — often whipping them with a piece of sun-dried hippopotamus hide called a chicotte, chopping off their hands and heads, or killing them by dozens at a time. In his recent study of the Congo, King Leopold's Ghost, the historian Adam Hochschild estimates that during the period of Leopold's pillage of the Congo, the population dropped by ten million people. Disease, starvation, a low birth rate, and outright murder all combined to turn the Congo into what Heart of Darkness later portrayed as a "nightmare." Some observers of the atrocities committed there — such as E. D. Morel and Sir Roger Casement — became noted anti-Leopold activists and launched semi-successful campaigns to end Leopold's rule. Other observers transformed what they saw into art — as did Joseph Conrad when he wrote Heart of Darkness.
Leopold's Congo and the people — White and Black — who populated it find their way into the pages of Conrad's novel. The ominous Company that hires Marlow, for example, is a thinly veiled depiction of Leopold's operations in Africa. Leopold's agents become the "faithless pilgrims" looking for riches that Marlow describes once he reaches the Congo, and the chain gang Marlow sees at the Outer Station is a glimpse at the slavery enforced by Leopold's agents. Kurtz, the "first class agent" who commits numerous acts of savagery (including the placing of "rebel" heads upon posts surrounding his hut) is an embodiment of the collective horrors that Conrad witnessed firsthand. As Marlow tells his audience on board the Nellie, "In the blinding sunshine of that land I would become acquainted with a flabby, pretending, weak-eyed devil of a rapacious and pitiless folly." The "devil" in this context is the greed that motivated Leopold to continue the systematic ravaging of the Congo and its people for more than twenty years.