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 60,000 in Niger. In the Ivory Coast, they are concentrated in the cities of Abidjan (Treichville, Adjamé), Bouake, Korhogo, Grand Bassam and Gagnoa where they are mostly employed in retail at major markets. Otherwise known as "Anago traders", they dominate certain sectors of the retail economy. The Yorubas are the main ethnic groups in the Nigerian federal states of Ekiti, Lagos, Ogun, Ondo, Osun, Kwara, Oyo, the western third of Kogi and the Akoko parts of Edo. The chief Yoruba cities or towns in Nigeria are: Abẹokuta, Abigi, Ado-Ekiti, Agbaja, Ago iwoye, Akungba-akoko, Akurẹ, Atan-otta, Ayetoro, Ayetoro gbede, Badagry, Ede,