Oyo Empire metropolitan Oyo. This may have been fine in the 15th century when Oyo controlled only its heartland. But to make and maintain farther conquest, the structure underwent several changes. Oyo maintained a semi-standing army of specialist cavalry soldiers called the "Eso", the "Esho" or, formally, the Eso of Ikoyi. These were 70 junior war chiefs who were nominated by the Oyo Mesi and confirmed by the Alaafin of Oyo. The Eso were appointed for their military skill without regard to heritage and were led by the Are-Ona-Kakanfo. After Oyo's return from exile, the post of Are-Ona-Kakanfo was established as the
Oyo Empire balances on the power of the Alafin and the Oyo Mesi and thus no one is arrogated absolute power. The Ogboni was a very powerful secret society composed of freemen noted for their age, wisdom and importance in religious and political affairs. Its members enjoyed immense power over the common people due to their religious station. A testament to how widespread the institution was is the fact that there were Ogboni councils at nearly all sub-courts within Yorubaland. Aside from their duties in respect to the worship of the earth, they were responsible for judging any case dealing with the