History of Africa usually governed by an "oba" and an "iwarefa", a council of chiefs who advised the "oba." by the 18th century, the Yoruba city-states formed a loose confederation, with the "Oni" of Ife as the head and Ife as the capital. As time went on, the individual city-states became more powerful with their "obas" assuming more powerful spiritual positions and diluting the authority of the "Oni" of Ife. Rivalry became intense among the city-states. The Oyo Empire rose in the 16th century. The Oyo state had been conquered in 1550 by the kingdom of Nupe, which was in possession of cavalry,
Abiodun (Oyo ruler) Adeyemi. A prominent contemporary descendant was Dr. Ameyo Adadevoh. Abiodun (Oyo ruler) Abiodun (reigned 1770–1789) was an 18th-century "alaafin," or ruler, of the Oyo people in what is now Nigeria. Coming to the throne shortly after the Oyo subjugation of neighboring Dahomey, Abiodun soon found himself embroiled in a civil war over the goals of the newly wealthy state. Bashorun Gaha, the empire's prime minister and lord marshal, had used his power to pervert the constitutional terms of abdication in a bid to limit the powers of the "Alaafin" and gain more political power for himself. During Gaha's power play,