Although the writings of Bahrey are sadly too brief for a deeper history of the Oromo peoples of the 16th century, his History of the Galla is a fascinating document. As an early ethnographic document of sorts, the Ethiopian monk sought to elucidate the social structure of the Oromo and its role in their often victorious raids and battles with Solomonic Ethiopia. Furthermore, in spite of his own Christian biases and panegyrical allusions to Sarsa Dengel's military prowess and zeal for Christian expansion, Bahrey strikes the modern reader as a relatively balanced source on the Oromo. He blames the small size of the Ethiopian warrior class and the egalitarian (or relatively so) Oromo social system in which all men are reared for war.
If true, this meant the Oromo age-grade system and their lubas were able to expand and raid several parts of the Solomonic kingdom due to their large source of warriors. Their social system also, according to the end of Bahrey's brief account, included a division of labor on the behalf of the village or community. Their system, though lacking the kind of permanent centralized authority of the Abyssinians or the later Oromo kingdoms, was flexible and able to adapt to different conditions. For instance, the adoption of horses and mules under Mesle in the years 1554-1662 represented an innovation in Oromo military tactics. Thus, it is less surprising to understand how and why the Oromo migrations of the 16th century were so successful, despite occasional internal disputes or divisions.
The success of the Oromo and the Solomonic dynasty's struggles to contain them during the 16th century remind us of other African states facing similar problems during the same era. The infamous "Jagas" of Kongo, for instance, appear to have formed effective warbands that allowed them to threaten Kongo and other kingdoms in West Central Africa. The Songhai, in West Africa, had Fulani marauders and other issues. Borno, under the Sayfawa dynasty, was also dealing with ongoing rebellions or insecurity near Lake Chad. According to Ahmad b. Furtu, whose chronicles of Idris b. Ali's military campaigns in Kanem and Borno have survived for posterity, the Sayfawa mais had to deal with the rebellious Bulala in Kanem, Tuareg incursions, Kano raids, and attacks from Sao populations near the imperial capital. Like Sarsa Dengel, Idris b. Ali appears to have been quite effective as a military leader. The displaced populations, war captives, and nearly exterminated peoples who felt the wrath of Borno were, for the most part, pacified or reduced to tributary status.
Unlike the Solomonic rulers, Borno appears to have been far more effective at securing its internal borders by the late 16th century. Part of this must have been due to the different socioeconomic structures of their respective enemies, as well as internal factors like military tactics, adoption of firearms, and administrative practices. One wonders what the Sayfawa would have done if faced with an enemy comparable to the Oromo peoples of the 16th century. The closest enemy might have been the Tuareg along the northwestern border and some of the Tubu and Arab populations in Kanem who were initially aligned with the Bulala sultans. We know Idris b. Ali, at least, won over some of the latter two groups and was able to force some of the Tuareg raiders into vassal status.