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,
Nupe people Nupe people The Nupe, traditionally called the Tapa by the neighbouring Yoruba, are an ethnic group located primarily in the Middle Belt and northern Nigeria, and are the dominant group in Niger State, an important minority in Kwara State and present in Kogi State as well. The Nupe trace their origin to Tsoede who fled the court of Idah and established a loose confederation of towns along the Niger in the 15th century. The proximity of Nupe to the Yoruba Igbomina people in the south and to the Yoruba Oyo people in the southwest led to cross-fertilization of cultural influences