Oyo Empire culture in Oyo where victory was obligatory and defeat carried the duty of committing suicide. This do-or-die policy no doubt contributed to the military aggressiveness of Oyo's generals. The Oyo Empire was the only Yoruba state to adopt cavalry; it did so because most of its territory was in the northern savannah. The origin of the cavalry is disputed; however, the Nupe, Borgu and Hausa in neighboring territories also used cavalry and may have had the same historical source. Oyo was able to purchase horses from the north and maintain them in metropolitan Oyo because of partial freedom from the
Oyo Empire layer of the empire was composed of the towns closest to Oyo-Ile, which were recognized as brothers. This area was south of metropolitan Oyo, and its Yoruba inhabitants spoke different dialects from that of Oyo. These tributary states were led by their own rulers, titled Obas, who were confirmed by the Alaafin of Oyo. The empire's third layer was the Egbado Corridor southwest of Yorubaland. This area was inhabited by the Egba and Egbado, and guaranteed Oyo's trade with the coast. The Egba and Egbado tributaries were allowed, like their Yoruba counterparts, to rule themselves. They were, however, supervised by