The peculiar politics of the Horn of Africa derives from the region’s exceptional pattern of state formation. At its center, Ethiopia was Africa’s sole indigenous state to remain independent through the period of colonial conquest, and also imposed its rule on areas not historically subject to it. The Somalis, most numerous of the pastoralist peoples, were unique in rejecting the colonial partition, which divided them between British and Italian Somalilands, French Djibouti, Kenya, and Ethiopia, while formerly Italian Eritrea, incorporated into Ethiopia in the post-World War II settlement, retained a sense of separate identity that fueled a long struggle for independence. These differences, coupled with the 1974 revolution in Ethiopia, led to wars that culminated in 1991 in the independence of Eritrea, the collapse of the Somali state, and the creation in Ethiopia of a federal system based on ethnicity. Developments since that time provide a distinctive slant on the legacies of colonial rule, the impact of guerrilla warfare, the role of religion in a region divided between Christianity and Islam, the management of ethnicity, and external intervention geared to largely futile attempts at state reconstruction. The Horn continues to follow trajectories of its own, at variance from the rest of Africa.