In a sense, you can say that the British were the cause of the Biafran Civil War which happened in Nigeria from 1967 to 1970. It was British colonialism which was the ultimate cause of the war.

When the British (along with other European nations) colonized Africa, it split its territories on that continent up into different colonies based on its own interests. In other words, Britain did not go around figuring out which areas really belonged together. Instead, they simply drew lines on the map, creating new political entities that had never existed before. Nigeria was one such entity.

When the British drew the map of what would become Nigeria, they included areas that were dominated by a variety of different ethnic groups. Two of the main ethnic groups whose areas were lumped together into Nigeria were the Hausa and the Igbo. There were many differences between these groups. For example, the Hausa were Muslim and had a system of government that was relatively feudal. By contrast, the Igbo were mainly Christian and had a more democratic society. These two groups did not have any natural ties that would make it reasonable to put them together into one country. However, the British lumped them together, creating Nigeria.

In 1960, Nigeria became independent. This led to conflicts between the Hausa and the Igbo as to who should have power in the new country. The conflicts between them eventually led the Igbos in the Southeast to secede from Nigeria. They formed a new country that they called Biafra. The war was fought to prevent the secession and to force that region back into the country of Nigeria.

The war was successful and Nigeria returned to its previous boundaries. However, the conflicts between the ethnic groups did not stop. Even today, there are conflicts between these groups. These conflicts help to make Nigeria somewhat politically unstable and they help to retard its economic and political development.