The Biafran Civil War; One Million People Die

On May 30, 1967 Lt-Col. Ojukwu officially declared the secession of the old Eastern Region, and called his new country "Biafra".
 
The federal armed forces re-organised themselves in June 1967. Gowon was promoted to Major-General, and other officers were also promoted in preparation of the war against Biafra. And federal forces launched their offensive in Biafra in July 1967. The Biafran War dragged on for some two and a half years, ending in January 1970 when Ojukwu escaped to the Ivory Coast.
 
An estimated one million people, most of them Biafran civilians, died during the war-making it the most calamitous civil war in post-independence Africa. In the first place, what actually prompted the secession?

National Movements and New States in Africa