West Africa a priest-king called as an Eze Nri. The Eze Nri managed trade and diplomacy on behalf of the Nri people and possessed divine authority in religious matters. The Oyo Empire was a Yoruba empire of what is today Western and North central Nigeria. Established in the 15th century, the Oyo Empire grew to become one of the largest West African states. It rose through the outstanding organizational skills of the Yoruba, wealth gained from trade and its powerful cavalry. The Oyo Empire was the most politically important state in the region from the mid-17th to the late 18th century, holding
Oyo Empire or Oyo-oro). The two most important structures in Oyo-Ile were the 'Afin,' or palace of the Oba, and his market. The palace was at the center of the city close to the Oba's market called 'Oja-Oba'. Around the capital was a tall earthen wall for defense with 17 gates. The importance of the two large structures (the palace and the Oja Oba) signified the importance of the king in Oyo. Oyo had grown into a formidable inland power by the end of the 14th century. For over a century, the Yoruba state had expanded at the expense of its neighbors.