In January 1966, he became Nigeria's youngest military chief of staff at the age of 31, because a military coup d'état by a group of junior officers under Major Chukwuma Kaduna Nzeogwu led to the overthrow of Nigeria's civilian government. In the course of this coup, mostly northern and western leaders were killed, including Sir Abubakar Tafawa Balewa, Nigeria's Prime Minister; Sir Ahmadu Bello, Sardauna of Sokoto and Premier of the Northern Region; and Samuel Akintola, Premier of the Western Region, Lt Col Arthur Unegbe and so many more. The then Lieutenant Colonel Gowon returned from his course at the Joint Staff College, Latimer UK two days before the coup – a late arrival that possibly exempted him from the plotters hit list. Success in twentieth century world affairs since 1919 and the subsequent failure by Major General Johnson Aguiyi-Ironsi (who was the head of state following the January 1966 coup-with Gowon his Chief of Staff) to meet Northern demands for the prosecution of the coup plotters further inflamed Northern anger. There was significant support for the coup plotters from both the Eastern Region as well as the mostly left-wing "Lagos-Ibadan" press.