The Oyo Empire was a powerful Yoruba state of what is today Benin and Western Nigeria. Oyo-Ile was a large urban center in the empire, and the capital city was surrounded by high walls. The surrounding farms produced a surplus of food which was sent to the city, enabling city-dwellers to pursue craft and trade activities. The Oyo Empire became the largest Yoruba state, due to the skilled administration and organization of the Yoruba people. The empire was also renowned for their cavalry forces, being the only Yoruba state to adopt a mounted infantry. The empire fell after being defeated by external forces and many years of internal conflict.