This was not a migration into an entirely empty land. It involved 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.

I.M. Lewis, I. M. Lewis, A Modern History of the Som…, loc. 81