History of Nigeria city-states. A state council (the "Oyo Mesi") named the "Alaafin" (king) and acted as a check on his authority. Their capital city was situated about 100 km north of present-day Oyo. Unlike the forest-bound Yoruba kingdoms, Oyo was in the savanna and drew its military strength from its cavalry forces, which established hegemony over the adjacent Nupe and the Borgu kingdoms and thereby developed trade routes farther to the north. The Benin Empire (1440–1897; called "Bini" by locals) was a pre-colonial African state in what is now modern Nigeria. It should not be confused with the modern-day country called Benin,
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