On September 20, 1967, the Nigerian 2nd Division under General Murtala Mohammed forced all Biafran soldiers within Nigeria's Mid-Western Region to retreat eastwards back towards Biafra. In an attempt to halt the Nigerian advance retreating Biafran soldiers destroyed the River Niger Bridge at Onitsha, trapping the Nigerians on the other side of the river. In October 1967 2nd Division soldiers entered Asaba and began setting up artillery positions on the banks of the Niger River while 2nd Division soldiers began preparing for an invasion.

 

The Biafran 11th Division, which consisted of the 11th, 12th and 18th Battalions, was given the task of defending Onitsha. The 12th Battalion under Col. Mike Inveso was responsible for defending the area between Idah and Nsugbe, the 18th Battalion under Col. Assam Nsudoh was responsible for defending Onitsha town, and the 11th Battalion under Maj. Joseph Achuzie defended the area between Atani and Ndoni. The beaches around Onitsha were heavily mined and were backed up by Biafran machine guns and anti-tank weapons. Because the Biafrans had detonated the Niger River Bridge Gen. Murtala Mohammed was left with the decision of crossing the Niger River at Idah or making and amphibious attack on Onitsha. Gen. Mohammed disregarded advice from the Nigerian Army HQ in Lagos and chose to attack Onitsha head on. On October 4, 1967, Gen. Mohammed ordered Nigerian artillery to begin bombarding Onitsha. Eight days later Gen. Mohammed personally led a 10-boat armada carrying 5,000 Nigerian soldiers across the Niger River into Onitsha. The Biafran 18th Battalion resisted stubbornly but were forced to retreat in disarray. However, instead of pursuing the retreating Biafrans and occupying the town the Nigerians turned their attention to looting and burning the Onitsha Market to the ground. This gave the 18th Battalion time to reorganize and make a counter-attack. The 11th Battalion under Maj. Achuzie made their way up the New Market road while the 18th Battalion under Col. Nsudoh swung down the Old Market road towards Onitsha. Nigerian 2nd Division soldiers stationed in Onitsha were totally routed and most were either killed or taken prisoner. Undaunted, Gen. Mohammed ordered a 5,000 man reserve from Lagos to cross the Niger River into Onitsha but they were once again defeated. Gen. Mohammed ordered troops under Lt. Col. Ipoola Alani Akinrinade to make a third assault on Onitsha but were once again thwarted by the Biafran 11th and 18th Battalions. It was now when Gen. Mohammed realized there was no hope in attacking Onitsha from Asaba and he began the audacious task of heading towards Idah in the North.