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
Yoruba people variety taught in schools and spoken by newsreaders on the radio, has its origin in the Yoruba grammar compiled in the 1850s by Bishop Samuel Ajayi Crowther, who himself was a creole from Sierra Leone. Though for a large part based on the Oyo and Ibadan dialects, it incorporates several features from other dialects. As of the 7th century BCE the African peoples who lived in Yorubaland were not initially known as the Yoruba, although they shared a common ethnicity and language group. By the 8th century, a powerful Yoruba kingdom already existed in Ile-Ife, one of the earliest in