Before an angry radical white guy
decided he liked the sound of the name, Biafra was a short-lived secessionist republic
that attempted to break off from Nigeria
The Christian-Muslim conflict in Nigeria that we see today (much of the north subscribes to Sharia, which offends the secular national government greatly) is, as in much of Africa, overlaid on long-standing tribal rivalries. In late 1966, attacks on non-Muslim Igbo settlers in the north had reached a fever pitch. The Igbo-dominated Eastern Region (now roughly the East-Central, South-Eastern, and Rivers states) started openly talking secession as refugees flooded in, led by regional military officers. Conversely, non-Igbo started leaving the East as they felt their societal position would be compromised by the new arrivals. Although talks were held starting in early 1967 to settle the disputes that were driving Igbo into the East, reconcile between the Eastern military and federal political leaders proved impossible. Eastern Region military governor Lt. Col. Chukwuemeka Odumegwu Ojukwu proclaimed the Republic of Biafra on 30 May 1967, speaking of anti-Igbo bias in the federal government and hinting at cases of genocide.
Civil war immediately ensued. Biafra's only national asset was its southern oil fields in a non-Igbo area, and the Nigerian government successfully managed to take those back and win over the local tribes fairly quickly. The remaining territory, while ethnically nearly homogenous, was not even capable of producing its own food, and thus international aid was solicited. Food aid came from many NGOs in the United States and Western Europe, responding to Biafran propaganda; some of these same organizations provided munitions, although most came on the international arms market via France and its former colonies. Biafra was also a mercenary's paradise, as referenced in Warren Zevon's 1978 song Roland the Headless Thompson Gunner. On the other side, Nigeria was aided by a strange duo: the United Kingdom provided mostly diplomatic assistance, while the Soviet Union shipped in military equipment. The United States officially stayed out of this conflict.
A bloody stalemate held for much of two years. Much like the South in the American Civil War, the Biafrans were undersupplied and ill-fed, but held the advantage in leadership and morale. Like the South, though, Biafra eventually broke under the strain as Nigeria brought its superior resources to bear. Several battlefield reverses in late 1969 led to Lt. Col. Ojukwu's escape to Ivory Coast (now Côté d'Ivoire) and the remaining leaders' quick surrender to federal forces on 15 January 1970. Very little evidence of genocide was found by international inspectors after the war, contrary to Ojukwu's propaganda efforts; the reintegration of Igbo into the nation and reconstruction of the war-torn areas went fairly smoothly over a three-year transition period.
Biafra, Columbia Encyclopedia, 5th ed., as quoted on above page