Nzeogwu was born in the Northern Region’s capital of Kaduna to Igbo parents from Okpanam Town, near Asaba in the present day Delta State. He was an Infantry and Intelligence Officer of the Nigerian Army who eventually became the Chief Instructor at the Nigerian Defence Academy in Kaduna.
The forerunner of the Nigerian Army Intelligence Corps (NAIC) was the Field Security Section (FSS) of the Royal Nigerian Army, which was established on 1 November 1962 with Captain PG Harrington (BR) as General Staff Officer Grade Two (GSO2 Int). The FSS was essentially a security organization whose functions included vetting of Nigerian Army (NA) personnel, document security and counter intelligence. Major Nzeogwu was the first Nigerian Officer to hold that appointment from November 1962 to 1964 and the first to stage a bloody military coup.
Nzeogwu was an ambitious young military officer and a Roman Catholic. His Hausa colleagues in the Nigerian Army gave him the name “Kaduna” because of his love with the town.
In the early hours of January 15, 1966, Nzeogwu led a group of mostly Northern soldiers on a supposedly military exercise and led them to attack the official residence of the premier of the North, Sir Ahmadu Bello in a bloody Coup that saw the murder of the Premiers of Northern and Western Nigeria. The Prime Minister, a Federal Minister, two Regional Premiers, and top Army officers from the Northern and Western regions of the nation were brutally murdered. The premier of the Eastern region (where most of the plotters came from), the Igbo President of Federation and the Igbo Army Chief were the only notable individuals spared (ONE OF THE GENESIS OF THE CONCURRENT TRIBAL DIVISION).
The coup failed, and Nzeogwu was later arrested in Lagos on January 18, 1966. He was in the company of Lt. Col. Conrad Nwawo.
On May 30, 1967 Biafra declared its independence from Nigeria, this was spurned by the incessant killing of Igbos in Northern Nigeria and refusal of then military Head of State General Yakubu Gowon (Hausa) to mobilize security personnel to stop the killings. Nzeogwu was released from close observation, and asked to go into battle on the side of the Biafrans.
On July 29, 1967, Nzeogwu - who had been promoted to the rank of a Biafran Lt. Colonel - was trapped in an ambush near Nsukka while conducting a night reconnaissance operation against federal troops of the 21st battalion under Captain Mohammed Inuwa Wushishi.
He was killed in action and his corpse was subsequently identified. After the defeat of Biafra and the end of the war, orders were given by the Head of the Nigerian government, Major General Yakubu Gowon, for him to be buried at the military cemetery in Kaduna with full military honours.