Conrad may have been thinking of the speech with which King Leopold II of Belgium opened his geographical conference on Central Africa in September 1876: 'To open to civilization the only part of the globe where it has yet to penetrate, to pierce the darkness which envelopes whole populations, it is, I dare to say, a crusade worthy of this century of progress.'
Leopold's real motives for founding the Congo Free State, however, were far from altruistic: financial gain, regardless of the human cost, was the king's sole ambition. Leopold's attention had been drawn to Central Africa by a report in The Times (11 January 1876) headed 'African Exploration', which described the interior of Africa as 'a magnificent and healthy country of unspeakable richness' that would 'repay any enterprising capitalist that might take the matter in hand.'
In contrast to the cynical Marlow, Conrad's letters prior to his departure for the Congo suggest he too had been taken in. The first denunciation of the regime’s brutality was not written until Conrad was there, and it was not published until shortly after he had returned to Europe. By then, of course, Conrad had already witnessed some of it first hand.