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 within and outside of Yorubaland. It was divided into four layers defined by relation to the core of the empire. These layers were Metropolitan Oyo, southern Yorubaland, the Egbado Corridor and Ajaland. Metropolitan Oyo corresponded, more or less, to the Oyo state prior to the Nupe invasion. This was the hub of the empire, where the Yoruba spoke the Oyo dialect. Metropolitan Oyo was divided into six provinces, with three on the west side of the Ogun River and three to the river's east. Each province was supervised by a governor appointed directly by the Alaafin of Oyo. The second