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,
Oyo Empire Oyo Empire, usually the Alaafin's oldest son succeeded his father to the throne. But, this sometimes led to the oldest son, i.e. the first-born prince, the Aremo, hastening the death of his father. Independently of the possible succession, the Aremo was quite powerful in his own right. For instance, by custom, the Alaafin abstained from leaving the palace, except during the important festivals, which in practice curtailed his power. By contrast, the Aremo often left the palace. This led noted historian S. Johnson to observe: "The father is the king of the palace, and the son the King for the