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
Nigeria of Igbo culture. Nri and Aguleri, where the Igbo creation myth originates, are in the territory of the Umeuri clan. Members of the clan trace their lineages back to the patriarchal king-figure Eri. In West Africa, the oldest bronzes made using the lost-wax process were from Igbo-Ukwu, a city under Nri influence. The Yoruba kingdoms of Ife and Oyo in southwestern Nigeria became prominent in the 12th and 14th centuries, respectively. The oldest signs of human settlement at Ife's current site date back to the 9th century, and its material culture includes terracotta and bronze figures. Oyo, at its territorial