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
History of the Yoruba people amala (yam flour). The ethnic group also holds musical and cultural festivals. The Yoruba eventually established a federation of city-states under the political ascendancy of the city state of Oyo, located on the Northern fringes of Yorubaland in the savanna plains between the forests of present Southwest Nigeria and the Niger River. Following a Jihad led by Uthman Dan Fodio and a rapid consolidation of the Hausa city states of contemporary northern Nigeria, the Fulani Sokoto Caliphate invaded and annexed the buffer Nupe Kingdom. It then began to advance southwards into Ọyọ lands. Shortly afterwards, its armies overran the Yoruba