On September 20, 1967, the Nigerian 2nd Division under General Murtala Muhammed forced all Biafran soldiers within Nigeria's Mid-Western Region to retreat eastwards towards Biafra.

In October 1967, 2nd Division soldiers entered Asaba and began setting up artillery positions on the river banks and preparing for an invasion.

While Nigerian Army headquarters in Lagos and some of his subordinates advised Muhammed to pursue the safer second option, he refused owing to his longstanding rivalry with 1st Division commander Colonel Mohammed Shuwa.

Lieutenant Colonel Frank Aisida, a bigrade commander within the 2nd Division, was so convinced of the danger and futility of a direct assault across the river that he refused to take part.

On November 19, 1967, pilots from the Soviet Union and United Arab Republic flying MiG-17s began bombing areas around Onitsha, devastating the population.

The Biafran 11th Division under Maj. Joseph Achuzie fought fiercely against the Nigerians and managed to hold them off for over three months before Abagana was captured on March 20, followed by Onitsha less than 24 hours later.