Oyo Empire 17th century, Oyo began a long stretch of growth, becoming a major empire. Oyo never encompassed all Yoruba-speaking people, but it was the most populous kingdom in Yoruba history. The key to Yoruba rebuilding of Oyo was a stronger military and a more centralized government. Taking a cue from their Nupe enemies (whom they called "Tapa"), the Yoruba rearmed with armor and cavalry. Oba Ofinran, Alaafin of Oyo, succeeded in regaining Oyo's original territory from the Nupe. A new capital, Oyo-Igboho, was constructed, and the original became known as Old Oyo. The next oba, Eguguojo, conquered nearly all of Yorubaland.
Oyo Empire the Alaafin of Oyo was supreme overlord of the people, he was not without checks on his power. The Oyo Mesi and the Yoruba Earth cult known as Ogboni kept the Oba's power in check. The Oyo Mesi spoke for the politicians while The Ogboni spoke for the people backed by the power of religion. The power of the Alaafin of Oyo in relation to the Oyo Mesi and Ogboni depended on his personal character and political shrewdness. The Oyo Mesi were seven principal councilors of the state. They constituted the Electoral Council and possessed legislative powers, similar to today's