Which region declared its independence from Nigeria in 1967 and was unsuccessful?

In May 1967, the Eastern Region declared independence as a state called the Republic of Biafra, under the leadership of Lt. Colonel Emeka Ojukwu. The Nigerian Civil War began as the official Nigerian government side (predominated by soldiers from the North and West) attacked Biafra (Southeastern) on 6 July 1967 at Garkem. The 30-month war, with a long siege of Biafra and its isolation from trade and supplies, ended in January 1970. Estimates of the number of dead in the former Eastern Region are between 1 and 3 million people, from warfare, disease, and starvation, during the 30-month civil war.

France, Egypt, the Soviet Union, Britain, Israel, and others were deeply involved in the civil war behind the scenes. Britain and the Soviet Union were the main military backers of the Nigerian government while France and others aided the Biafrans. Nigeria used Egyptian pilots for their air force.