African rulers enjoyed the benefits of slavery for a long period in Nigeria’s history. Prior to the infamous slave trade across the Atlantic, slavery already existed in the African continent. The African rulers and the most influential people in Nigeria captured male and female slaves in wars and used them as workers in their farmlands. Slavery enabled the ruler to use cheap labor and force the slaves to work at their instructions. The pre-existing slavery in Nigeria was an important cause of the slave trade because it was easier for Europeans and American slave traders to introduce the slave trade to Nigeria.

The trans-Atlantic slave trade in Nigeria existed for over five centuries. The slave trade in Nigeria began in the 16^th century and ended in the late 19^th century. At the beginning of the slave trade, the sale brought some short-term benefits to some African states and the rulers. In the slave trade, slaves were regarded as property that could be bought and sold freely. The slave traders in southern Nigeria looked for and captured slaves to sell them to the buyers. States locate by the coastal line gained enormous profits by selling slaves to European buyers. Since Nigeria is located by the western coastline of Africa, the rulers in Nigeria obtained guns and money in exchange for these slaves. When the proposal of abolishing the slave trade was spreading throughout the western world, the African rulers encountered obstacles that prevent them from collecting wealth.

In the long run, slavery adversely affected African ruler’s power and authority in Nigeria, because slavery made African rulers gradually lose control over the country. Most of the impacts on Africa caused by the slave trade were negative. During this period, millions of Africans were captured and transferred to work as laborers in the plantations in the Americas. The slave-trading involved violence and caused significant damages to African people and society. For example, the slave trade caused a shortage of male labors remaining in Africa. The shortage of workforce obstructed the economic development in Africa. Moreover, the slave trade created the conditions for the subsequent colonial conquest of Africa by the British colonists. In the late 19^th century, the Nigerian rulers did not have the capacity to resist the Europeans in the colonizing process and gradually lost control over the land. Regardless of the efforts of many African communities to defend themselves against slave traders, African states eventually collapsed. In 1903, the British conquered entire Nigeria’s territory. Nigeria became a British colony and was under British control. Even though the local African rulers were given a certain level of authority over some affairs, the local rulers were forced to permit the colonial government to conduct its business and gather taxation.