United Nations Operation in the Congo
Later in 1960, Aguiyi-Ironsi headed the Nigerian contingent force of the United Nations Operation in the Congo. From 1961 to 1962, Aguiyi-Ironsi served as the military attaché to the Nigeria High Commission in London, United Kingdom. During this period he was promoted to the rank of brigadier. During his tenure as military attaché he attended courses at the Imperial Defence college (renamed Royal College of Defence Studies in 1961), Seaford House, Belgrave Square. He was appointed a Member of the Order of the British Empire, Military Division (MBE) in the 1962 New Year Honours list.