Oyo, the great exporter of slaves in the eighteenth century, collapsed in a civil war after 1817, and by the middle of the 1830s the whole of Yorubaland was swept up in these civil wars. New centers of power--Ibadan, Abeokuta, Owo, and Warri--contested control of the trade routes and sought access to fresh supplies of slaves, which were important to repopulate the turbulent countryside. At this time, the British withdrew from the slave trade and began to blockade the coast (see Abolition of the Slave Trade , this ch.). The blockade required some adjustments in the slave trade along the lagoons that stretched outward from Lagos, while the domestic market for slaves to be used as farm laborers and as porters to carry commodities to market easily absorbed the many captives that were a product of these wars.

War and slave raiding were complementary exercises among the Yoruba, who needed capital to buy the firearms with which they fought in a vicious cycle of war and enslavement. Military leaders were well aware of the connection between guns and enslavement.

Some of the emerging Yoruba states started as war camps during the period of chaos in which Oyo broke up and the Muslim revolutionaries who were allied to the caliphate conquered northern Yorubaland. Ibadan, which became the largest city in black Africa during the nineteenth century, owed its growth to the role it played in the Oyo civil wars. Ibadan's omuogun (war boys) raided far afield for slaves and held off the advance of the Fulani. They also took advantage of Benin's isolation to seize the roads leading to the flourishing slave port at Lagos. The threat that Ibadan would dominate Yorubaland alarmed its rivals and inspired a military alliance led by the Egba city of Abeokuta. Dahomey, to the west, further contributed to the insecurity by raiding deep into Yorubaland, the direction of raids depending upon its current alliances.

Data as of June 1991