The attempted secession of the southeastern provinces of Nigeria was the cause of the Nigerian Civil War. Another name for this conflict is the Biafran War because those provinces named themselves the Republic of Biafra.

The province's reasons for secession were rooted in a number of political, religious and economic factors.

The seceding provinces were populated primarily by Igbo, an ethnic group that had long had democratic institutions. This contrasted strongly with the cultures of the north and the west, whose political traditions were more autocratic.

The southeastern provinces were also largely Christian, unlike those in northern and western Nigeria, which were predominantly Muslim. An onslaught of military coups, the last of which was carried out by officers without Igbo ties, exacerbated the situation.

Finally, the presence of oil in the Biafran lands was a powerful source of national income which, if lost, would be detrimental to all of the remaining regions of Nigeria.

Ethnic violence further destabilized the country. In an attempt to take control of the volatile situation, General Odumegwu Ojukwu declared the independence from Nigeria, calling for the creation of the Republic of Biafra on May 30, 1967. The Nigerian Civil War took place between July 6, 1967 and January 16, 1970 and claimed the lives of more than one million soldiers and civilians through fighting and famine. Biafra was ultimately reabsorbed into Nigeria.