The initial spread of Swahili from the coastal areas of Kenya and Tanganyika during the last century must, in large measure, be attributed to the Swahili traders, who, with their often unsavoury reputations and their caravans, took the language as far as the Congo. Where these traders settled in any numbers, as at Tabora, Mwanza, Ujiji, Usumbura, Lake Nyasa, and, to a smaller extent, at Mumias, small Islamic islands of coastal-Swahili-speakers have persisted: some flourishing like Usumbura, others, like Mumias, declining. In general, however, the language became more emasculated the farther it extended from the coast, so that in North Uganda and parts of the Eastern Congo it is essentially a highly simplified means of communication for individuals of widely differing groups; pruned of all refinements, its link with the coast is a tenuous one.