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 a large snake with a magic charm attached to its throat. The chief instructed Oranyan to follow the snake until it stopped somewhere for seven days and disappeared into the ground. Oranyan followed the advice and founded Oyo where the serpent stopped. The site is remembered as Ajaka. Oranyan made Oyo his new kingdom and became the first "oba" (meaning 'king' or 'ruler' in the Yoruba language) with the title of "Alaafin of Oyo" (Alaafin means 'owner of the palace' in Yoruba). He left all his treasures in Ife and allowed another king to rule there. At one time, Oyo-ile