Timothy Onwuatuegwu took part in the 1966 military coup which overthrew Nigerian Prime Minister Abubakar Tafawa Balewa while also killing many other Northern senior army officers.

Onwuatuegwu was put in control of a small band of soldiers whose main job was to assassinate any Nigerian officer or politician they deemed a threat Kaduna.

Although the coup was stopped by General Johnson Aguiyi-Ironsi both Onwuatuegwu and his superior Major Chukwuma Kaduna Nzeogwu were able to control the northern portion of Nigeria for a few weeks.

On 15 March 1969 Onwuatuegwu led an assault on the Nigerian 16th Division, who had been occupying Owerri since October 1968, but was forced to halt after suffering heavy casualties.

Achuzie's full-frontal attack ultimately failed and was forced to retreat and Ojukwu restored Onwuatuegwu as head of the S Division.

One account by his former co-conspirator Maj. Adewale Ademoyega states that he was tricked into attending a meeting at a hotel with federal officers of the 3rd Marine Commando Division.