It was located southwest of present-day Nigeria, and Oyo peaked in the 17th century. The empire rose as one of the biggest Yoruba-speaking empires based on factors such as an excellent geographical location, the use of Calvary, the trading system and good rulers.
The Oyo empire was headed by a king called Oba Alaafin of Oyo, who was a supreme ruler and was referred to as 'Alase Ikeji Orissa'. He was supported by a set of seven Chiefs called the Oyomesi.
A Chief led the Oyomesi called the Bashorun. They were powerful chiefs essential to the government of the King in the Oyo empire and had responsibilities to carry out.
The Empire operated on checks and balances, and no one had absolute powers. While the Oyomesi checked the Alaafin, another group checked the powers of the Oyomesi, which were the Ogboni.
During the time of Alaafin Orompoto, the old Oyo empire grew and flourished. Alaafin Orompoto used his wealth from trade to build a formidable empire that could conquer neighboring territories and collect tributes from them.
They were able to grow a big army. One of the Kingdoms conquered by the old Oyo empire was the Dahomey Kingdom. It was defeated twice in 1724-1730 and 1738-1748. The old Oyo empire grew in wealth and expanded in the territory.
The fall of the empire was gradual, and it started from civil crises that made the old Oyo empire lose its military strength, political disputes and other external factors. There was a power fight between Bashorun Gaa and the Oyomesi, which was the first cause of conflict in the old Oyo empire.
The Oyomesi was weakened during this period, and it affected the political structure of the kingdom. Another primary reason happened during the time of Alaafin Arole. It was a constitutional crisis, and it started during Arole's reign. These were the internal causes of the fall of the empire.
The external cause of the empire was the Invasion of the Fulani. The Fulani invaded the old Oyo empire after the defeat of Afonja, and that was how the old Oyo empire fell and was conquered.
Today, the Oyo kingdom still stands; however, in terms of strength and reach, it is not as it used to be.