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,
History of the Yoruba people been dealt a mortal blow. The other Yoruba city-states broke free of Oyo dominance, and subsequently became embroiled in a series of internecine conflicts that soon metamorphosed into a full scale civil war. These events weakened the southern Yorubas in their resistance to British colonial and military invasions. In 1960, greater Yorubaland was subsumed into the Federal Republic of Nigeria. The historical records of the Yoruba, which became more accessible in the nineteenth century with the more permanent arrival of the Europeans, tell of heavy Jihad raids by the mounted Fulani warriors of the north as well as of endemic