Joseph Conrad, author of Heart of Darkness, traveled in what is now the Democratic Republic of the Congo in Africa—the river is the Zaire. In Conrad time, it was called the Belgian Congo—he sailed the Congo River. Conrad's novel allows us to understand his feelings toward the "empire" and its treatment of the African natives.
In 1878, Leopold II of Belgium took over Africa—gaining wealth by stripping Africa's of its natural resources. In doing so, he and his "representatives" created conditions that were deplorable—
The Belgian traders committed many well-documented acts of atrocity against the African natives...
Leopold II was eventually forced from his place of power in Africa.
Charlie Marlow, the narrator of the story—and ship's captain—is struck by a world that makes little sense as he travels into the Congo. He finds many men on a quest for material gain; a casual and unfeeling exploitation of the natives; and, paranoia and insanity running throughout the Company—the organization that has sent Marlow into the Congo to bring back Kurtz, the Company's most successful man in delivering shipments of ivory more valuable than those of all the other agents put together.
When Marlow reaches the first stop, the Lower Station, he has stepped into a world where reason does not exist. The first thing he sees is scattered machinery, abandoned and rusting all over the ground...
...an undersized railway truck lying there on its back with its wheels in the air. One was off. The thing looked as dead as the carcass of some animal.
When Marlow looks up at the cliff, he witnesses the purposeless blasting of dynamite.
A heavy and dull detonation shook the ground, a puff of smoke came out of the cliff, and that was all. No change appeared on the face of the rock...the cliff was not in the way or anything...
Marlow turns at the sound of clinking behind him—noise from the chains that bind African "slaves." They are wearing rags "round their loins;" Marlow notes that they are so thin that their ribs stick out, as well as their joints; and, the iron "collar" each wears is connected to another's and they all move in tandem.
Marlow does not consider himself weak, but he is appalled at how the people have been treated.
They passed me within six inches...with [a] complete death-like indifference...
They were dying slowly—it was very clear.
At the Central Station, Marlow discovers that the manager and his nephew greatly resent Kurtz's success and they are paranoid about Kurtz's ability to send such an enormous amount of ivory out of the Inner Station—and the power it affords Kurtz.
In the Inner Station, Marlow finally finds Kurtz's "camp," and notes:
Now I had suddenly a nearer view, and its first result was to make me throw my head back as if before a blow... These knobs...were...expressive and puzzling...They would have been even more impressive, those heads on the stakes, if their faces had not been turned to the house.
Human sacrifices have also taken place, and Kurtz (worshipped as a God)—at one time brilliant—has lost his connection to humanity...he is insane.
All that motivates so many of the characters that Marlow encounters is an insatiable greed, fostered by the "empire," with a mindless destruction of the native population. Wealth matters more than human life. Marlow (and Conrad) abhors what the empire has done and his descriptions of the tormented Africans expose these human-rights violations to the world.