In August 1967, three months into the Biafran War, Biafran troops invaded the Mid-Western Region, to the west of the River Niger. They spread west, taking Benin City and reaching as far as Ore, where they were pushed back by the Nigerian Second Division, under the command of Col. Murtala Muhammed.
The Federal troops gained the upper hand, and forced the Biafrans back to the Niger, where they crossed the bridge back into the Biafran city of Onitsha, which lies directly across from Asaba. The Biafrans blew up the eastern spans of the Onitsha bridge, so that the Federal troops were unable to pursue them.
The Federal troops entered Asaba around October 5, and began ransacking houses and killing civilians, claiming they were Biafran sympathisers. Reports suggest that several hundred innocent males may have been killed individually and in groups at various locations in the town. Leaders summoned the townspeople to assemble on the morning of October 7, hoping to end the violence through a show of support for “One Nigeria.” Hundreds of men, women, and children, many wearing the ceremonial akwa ocha (white) attire paraded along the main street, singing, dancing, and chanting “One Nigeria.” At a junction, men and teenage boys were separated from women and young children, and gathered in an open square at Ogbe-Osowa village. Federal troops revealed machine guns, and orders were given, reportedly by Second-in-Command, Maj. Ibrahim Taiwo, to open fire. Most of the killing ended by 7 October.
The bodies of some victims were retrieved by family members and buried at home. But most were buried in mass graves, without appropriate ceremony. Many extended families lost dozens of men and boys. Federal troops occupied Asaba for many months, during which time most of the town was destroyed, many women and girls were raped or forcibly “married,” and large numbers of citizens fled, often not returning until the war ended in 1970.