An Cosantóir

An Cosantóir September / October 2026 www.military.ie/magazine 28 | An Cosantóir September / October 2026 www.military.ie/magazine 28 | M ichael Joseph Costello was born on 4 July 1904 in Cloughjordan to a family with a long tradition of teaching. His godfather was Thomas McDonagh who was later one of the leaders of the Easter Rising. Three of his siblings died during the influenza pandemic in 1917. Receiving his own schooling from the Christian Brothers in Nenagh, Costello briefly became a correspondent for the Midland Tribune aged sixteen but joined the Old IRA after his father was arrested by the Black and Tans. He participated in the War of Independence as an intelligence officer in north Tipperary. Costello joined the National Army in 1922 and at the outbreak of the Civil War was based in Portlaoise as a Lieutenant; his commanding officer was the popular Colonel-Commandant Austin MacCurtain (23), 'a man for whom [Costello] had great admiration' who was then Intelligence Officer for the Third Southern Command. In July 1922, a unit of Republicans ambushed a National Army column near Abbeyleix. MacCurtain led a unit from Portlaoise that included Costello, that were ambushed by the Republican party, killing MacCurtain and Colonel- Commandant Sean Collison. Costello and another officer turned the ambush and he personally captured seventeen Republicans. General Michael Collins arrived in Portlaoise shortly afterwards; Costello was struck by 'his capacity to extract information from all the people he was talking to and cross examining.' Collins quickly made the decision to fill MacCurtain's appointment by promoting Costello to Colonel-Commandant at the tender age of eighteen. He was subsequently modest with regard to this by noting that many young people were appointed to important positions at this time. Colonel Costello retained his rank after the Civil War when he was appointed National Army Director of Intelligence from 1924 until July 1926. He then participated in the Military Mission to the United States by attending the US Army Command and Staff College at Fort Leavenworth. He graduated with distinction which led to a recommendation that he attend the even more prestigious War College, then being attended by Major Dwight Eisenhower. Appointed to the Defence Plans Division on his return, Costello was also editor of the army magazine An t-Óglách, which he reformatted as a military academic journal. Costello was appointed Director of Training in 1931 and Commandant of the Military College in 1932, where he 'produced a first-class Military Instructional Institution turning out many high quality officers with Command and Staff ability, which proved so vital in the ensuing Emergency years.' Nicknamed LIEUTENANT LIEUTENANT GENERAL GENERAL M.J. COSTELLO M.J. COSTELLO ARTICLE BY PTE TERRY O'REILLY HISTORY

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