Gufu Oba has attempted a long and very ambitious survey of pastoralist migration, expansion, and warfare over the last seven centuries through a discussion of “warfare ecology,” the various social and environmental triggers of conflict, along seven “frontiers of warfare” from the Upper Nile (Nuer and Dinka) to the Horn of Africa (Somali and Oromo), the Central Rift Valley (Maasai), and the coastal hinterland of Kenya and Somalia.

In Part I, Oba first discusses the aspects of social and military organization along with the environmental factors which both drive expansion and ensure its success, and then sketches in the frontiers of conflict that structure his argument. However, although Oba has some interesting and pertinent observations to make regarding the existing literature, his overall argument never quite comes together. The failure here lies partly, perhaps, in the sheer span of time and space under consideration, which offers breadth but not depth. Other historians might be less confident in attributing dates and ethnic identities so far in the past and in treating concepts like “militarism,” “migration,” and “conquest” as though their meanings were uncontested and unchanging. Much of Oba’s discussion is necessarily based on secondary sources of variable age and reliability, which he seems to accept uncritically; the examples he uses are drawn without explanation or connection from a wide and eclectic range of societies. Moreover, since he is looking for commonalties rather than differences, the analysis becomes overly generalized. It is not clear what the author’s conclusions are, and the concept of “warfare ecology” itself fades into the background as the book progresses.

The real meat of the book is in Parts II and III, which present an extended discussion of the establishment and later collapse of a powerful southern Oromo presence in Jubaland and the coastal hinterland of Kenya. At the beginning of the nineteenth century, Oromo groups which had originally migrated from the Ethiopian borderlands dominated the southeastern interior; by the middle of the century, their dominant position, along with the grazing and wells on which it depended, was threatened by the expansion of the Darood alliance of Somali clans from the north and by Maa-speaking raiders from the west. By the end of the century, only small and beleaguered Orma (Oromo) communities survived in the Tana River valley: Jubaland (known to Oromo as Wama) was now Somali territory. This is an area where the author is on firm ground. The focus sharpens, the narrative tightens, and the analysis acquires depth and specificity, despite proofreading that at times is unacceptably slipshod. To some extent, this extended case study begins to address some of the questions raised but not fully explored at the beginning of the book.

The history of Somali expansion into Kenya and of the later attempts by the British to halt it east of the Tana River is superficially well-known, but Oba provides a far fuller picture, based in part on his own field and archival research on the Oromo communities which still survived. This allows the reader to view the region from an unfamiliar perspective. Hitherto, the Orma and Warda Oromo (“Galla”) have been marginal to a regional history dominated by Somali clans and coastal states and communities. Oba’s deep contextualisation restores their importance by linking them to both clients on the coast and other Oromo-speakers, including the Boran, further to the northeast. In one chapter, Oba looks closely at the socio-political process through which Boran were gradually forced to cede control over their wells in the Kenya/Ethiopia borderland to incoming Somali—with British acquiescence—and to move south. In two other chapters, he examines the fate of Southern Oromo who were incorporated into Somali clans as domestic slaves, either by capture or surrender, when their own communities in Wama scattered. He looks at how enslaved Oromo sought to develop and defend a distinctly separate, if subordinate, identity as Warda Oromo, and then to rejoin their kin, now the Orma, by crossing the Tana River into freedom. Here, the author suggests a fluidity of “ethnic” identity which is notably lacking in Part I. The process of Warda emancipation continued well into the 1960s, long after slavery on the Coast itself had disappeared.

In sum, readers looking for a new discussion of the factors making for pastoral expansion in Eastern Africa may find Herder Warfare frustrating and even disappointing, but those with an interest in the history of South Eastern Kenya and Southern Somalia between the Juba and Tana Rivers will find it both absorbing and thought-provoking.