On January 15, 1966, a small group of army officers, mostly southeastern Igbos, overthrew the government and assassinated the federal prime minister and the premiers of the northern and western regions. The federal military government that assumed power was unable to address ethnic tensions or produce a constitution acceptable to all sections of the country. Its efforts to abolish the federal structure greatly raised tensions and led to another coup in July. The coup-related massacre of thousands of Igbo in the north prompted hundreds of thousands of them to return to the southeast, where increasingly strong Igbo secessionist sentiment emerged.
In a move that gave greater autonomy to minority ethnic groups, the military divided the four regions into 12 states. The Igbo rejected attempts at constitutional revisions and insisted on full autonomy for the east. Finally, in May 1967, Lt. Col. Emeka Ojukwu, the military governor of the eastern region, who emerged as the leader of increasing Igbo secessionist sentiment, declared the independence of the eastern region as the "Republic of Biafra." The ensuing civil war was bitter and bloody, ending in the defeat of Biafra in 1970.
Following the civil war, reconciliation was rapid and effective, and the country turned to the task of economic development. Foreign exchange earnings and government revenues increased spectacularly with the oil price rises of 1973-74. On July 29, 1975, Gen. Murtala Muhammed and a group of fellow officers staged a bloodless coup, accusing Gen. Yakubu Gowon's military government of delaying the promised return to civilian rule and becoming corrupt and ineffective. General Muhammed replaced thousands of civil servants and announced a timetable for the resumption of civilian rule by October 1, 1979. Muhammed also announced the government's intention to create new states and to construct a new federal capital in the center of the country.
General Muhammed was assassinated on February 13, 1976, in an abortive coup. His chief of staff, Lt. Gen. Olusegun Obasanjo, became head of state. Obasanjo adhered meticulously to the schedule for return to civilian rule, moving to modernize and streamline the armed forces and seeking to use oil revenues to diversify and develop the country's economy. Seven new states were created in 1976, bringing the total to 19. The process of creating additional states continued until, in 1996, there were 36.
