In 1908 the Belgian state took over from Leopold II responsibility for the former Congo Independent State. This huge territory (2.5 million sq. km, one quarter the size of Europe) encompassed great ecological contrasts: savanna and woodland in the north and south, equatorial rainforest in the centre, and high mountains and plateaux in the east and south-east. Most people spoke languages of the Bantu family, but languages of several other types were spoken in the north-east. There were great differences in terms of social and pre-colonial political organisation, while by the end of the nineteenth century the expansion of trade had engendered six spheres of political and economic influence: the Luso-African zone bordering Angola; the Swahili zone in the east and south-east; the hills and pastures of the Great Lakes region; the Sudanese savanna in the north; the riverain zone between Stanley Pool (Lake Malebo) and Stanley Falls (Kisangani); the coastal triangle between Loango, the Teke plateau and Ambriz.

Colonial domination introduced new lines of division, and new attempts at integration. The frontiers of the territory posed one major problem. Although it had been formed as a result of explorations from both east and west coasts, the Congo Independent State had been left, after Partition, with only one point of access to the sea, where the Congo (now Zaire) river enters the Atlantic. The capital was sited here, at Boma, until 1929. Any attempt to strengthen economic or political links within the colony, and with the Belgian port of Antwerp, was bound to pull it westwards, turning it into an enormous funnel, in defiance of much economic and historical logic.