The political structure of Nigeria under the first military regime was unitary.
On May 24, 1966 the Federal Executive Council was renamed the Central Executive Council. This came into being as a result of the abolition of the Federal system of government and the substitution of a unitary system of government by the Supreme Commander of the Nigeria Armed Forces, Major General J.T.U. Aguiyi Ironsi.
Under this unitary system, the public service, both Federal and Regional were unified and the Regional governments abolished. The National Military Government rather than the Federal Military Government started to legislated for the whole country. This continued until Gowon's regime came in and brought back the Federal system of Government.