UNTIL THE late nineteenth century the history of the eastern Horn of Africa is dominated by the protracted Somali expansion from the north, and the rise and decline of Muslim emporia along the coast. To a certain extent each of these two themes has its own particular history, but at no time over the centuries was one entirely independent of the other. The gradual enlargement of their territory by the Somali was not achieved by movements in the hinterland only, nor were events on the coast without their effect in the interior. About the tenth century, however, when our brief account opens, the pressure of events ran from the coast towards the hinterland. But by the mid-nineteenth century, a state approaching equilibrium had been attained between the outward pressures of movements in the interior and the inward trend from the coast: if anything, indeed, the balance was tipped in favour of the hinterland which had come to exert a dominant political influence over the coastal settlements. For the history of the coast documentary evidence from various sources is available, at least in some periods; but for events in the hinterland the historian has to rely much more heavily upon the testimony of oral tradition. Fortunately, oral records are on the whole sufficiently abundant and consistent in their essentials, to enable the broad outlines of the Somali dispersal to be traced with what is probably a considerable degree of accuracy. Certainly the evidence at present available leaves no doubt that the gradual expansion over the last ten centuries of the Hamitic Somali from the shores of the Gulf of Aden to the plains of northern Kenya is one of the most sustained, and in its effects, far-reaching movements of population in the history of North-East Africa.

This was not a migration into an entirely empty land. It in-volved considerable displacements of other populations, and the Somali sphere was only extended by dint of continuous war and boodshed. Those who were mainly involved, other than the Somali, were the ethnically related Oromo peoples - or some of them - and a mixed negroid or Bantu population which, prior to the incursions of the Hamitic Galla and Somali, appears to have possessed part of the south of what is today the Somali Republic.