Costello, Michael Joseph (‘Mickey Joe’) (1904–86), army officer and public servant, was born 2 July 1904 in Cloughjordan, Co. Tipperary, the eldest of five boys and three girls (three of the children died of influenza in 1917) of Denis Costello of Kilmihill, Co. Clare, and Teresa Costello (née Moynihan) of Co. Offaly, who were both schoolteachers. His godfather was Thomas MacDonagh (qv), whom his father succeeded in his teaching post; MacDonagh wrote a poem entitled ‘The man upright’ about Denis Costello. Educated at the CBS at Nenagh, Costello became the Cloughjordan correspondent for the Midland Tribune at the age of sixteen but lost his job after writing a fictitious report of a meeting of the Borrisokane board of guardians, which he had not attended and which had unexpectedly not taken place.
In 1920 Denis Costello was arrested by the Black and Tans; his son immediately joined the IRA and became an intelligence officer for the North Tipperary battalion. In 1922 he joined the national army with the rank of lieutenant and was sent to Portlaoise to train cadets. On one occasion early in the civil war he and four other men were ambushed; although two of the men were killed and a third injured, Costello and the fifth man went after the twenty-three attackers and forced them to surrender. His action led to Costello's sudden promotion to the rank of colonel commandant by Michael Collins (qv), of which Costello himself later said: ‘It was a serious mistake on Collins's part. I was surprised he did it’.
Appointed intelligence officer of the 3rd southern command, Costello was transferred to Dublin when the command was abolished, and reduced to the rank of commandant. Shortly afterwards he was promoted to colonel and in October 1923 was appointed director of army intelligence at GHQ, Parkgate Street, Dublin. During this time he read widely on military history and the art of war. In 1925 he became chief staff officer and for seven months of 1926 attended the Command and Staff School at Fort Leavenworth, Kansas, USA, followed by five months at the office of industrial mobilisation in the US war department. In 1928 Costello and others from the Free State army visited the Staff Training College of the British army at Camberley in Surrey. Costello later recounted that Bernard Montgomery had tried to organise a protest against the visit but that Eric Dorman Smith (later Dorman O'Gowan (qv)) had ensured that the visitors were met with suitable dignity.
On his return from the USA, Costello was made director of military training (1931) and a member of the defence plan division. In 1933 he was promoted commandant of the Military College in the Curragh, and in 1938 assistant chief of staff to General Michael Brennan (qv). In May 1939 he revisited the USA to buy armaments but was stymied by Irish civil servants, who insisted that he purchase less advanced equipment from sources closer at hand. Following the outbreak of war in Europe he was given charge of the southern command in November 1939 with the rank of major general. As the GOC of the 1st (Spearhead) division he successfully launched, directed, and contributed articles to the defence forces’ magazine An Cosantóir. Despite de Valera's (qv) insistence on the importance of the southern ports to the state's security Costello concentrated much of his strength in the area of the Shannon estuary, believing the flying-boat base at Foynes and the new airport at Rineanna to be more important. Probably fuelled by these disagreements, persistent rumours circulated to the effect that Costello was planning a military coup. He retired from the army in 1945 and was invited by Tim O'Mahony to become general manager (1946) of the Irish Sugar Company.
Plagued by chronic industrial unrest the Irish Sugar Company had averaged two strikes a year since 1933 and it was in the middle of a strike when Costello was appointed. He believed that the key to running a company well was through good staff management, a view that was vindicated by his record, for, in contrast to the period before he took charge, there were no strikes in the twenty years that he was general manager. He helped to pacify the workers by establishing works councils in the company's four factories and by introducing an incentive scheme. He would later say that establishing good industrial relations was one of his fondest memories of his time with Irish Sugar.
Besides resolving the industrial relations issues, Costello realised that nobody above the rank of labourer knew how to grow sugar from beet. Adopting a scientific approach to seed breeding, lime production, and soil testing, he restored productivity and beet quality after the severe decline of the war years. He also sent all employees on courses to learn the manufacturing process, and actively encouraged the development of beet machinery suitable for Irish conditions. Investing heavily in research and development, he pioneered double cropping of rye grasses and root crops at the Gowla grass meal factory in Co. Roscommon. A member of the capital investment advisory committee (1956–7) established to advise on the size and composition of the public investment programme, Costello with Ruaidhrí Roberts (qv) of the Irish Trade Union Congress produced a minority report arguing for an increase rather than a cutback in public investment.
After his retirement Costello said that his second fondest memory of his time with the Irish Sugar Company was that the progress of the beet industry after the second world war helped to uplift the farming community. He firmly believed in the farming way of life and believed that much of the progress of Irish Sugar during his early years with the company was due to the establishment of the young farmers’ organisation Macra na Feirme by Stephen Cullinan (qv). Costello was of the opinion that this brought about a psychological revolution that was necessary to implement the technical revolution, which he saw as essential to the survival of Irish agriculture. His concern for the welfare of the Irish farmer was also demonstrated in his belief in the benefits of the co-operative movement; he actively associated himself with the horticultural developments of Fastnett (1963), Glencolumbkille, Kerry, and Swatagh. He was also a supporter of the co-operative established by Father James McDyer (qv) in Donegal.
Possibly ahead of his time, Costello established in 1959 Erin Foods, a convenience foods offshoot of the Irish Sugar Company. He believed that the parent company had the strong technical, capital, and manufacturing base to make such a project work. Costello saw the progress of the new company as part of the overall progress of the Irish state and nation. He envisaged a vast marketing drive to help expansion into the UK market and beyond, which would require an enormous financial undertaking. Although assured that the money would be forthcoming when Erin Foods was founded, he later claimed that the undertaking was sabotaged by the Department of Finance and that the political will did not exist to bankroll the project. He invested heavily in vegetable processing plants at Carlow, Thurles, and Tuam, but the lack of funds to market the new products abroad led to overproduction and massive losses for the new company. These losses were offset by the profits of Irish Sugar for a time, but in 1966 the parent company suffered its own losses owing to the fluctuation in the international price of sugar. Costello resigned in that year, frustrated by his inability to secure funding for the company. When he had joined the company in 1946 there were 720 employees and when he left there were more than 5,000. A former employee and sometime TD, Brendan Halligan, described the company as ‘alive and vibrant’ during Costello's period in charge. Sir Anthony O'Reilly later described Costello as a patriot and a bully whose ‘patriotism blinded him to the commercial realities of the marketplace’.
A member of the national agricultural council, after his retirement Costello took up farming in Roscommon with two of his sons, Donal and Denis. He was awarded an honorary LLD from the NUI in 1964. He was president of the International Institute for Beet Research and in 1973 was honoured by King Baudouin of Belgium for his services to the sugar beet industry internationally. He lectured extensively at home and abroad on agriculture and the co-operative movement and was vice-president of the Scottish Peat and Land Development Association. He was also vice-president of the Military History Society, in which capacity he actively opposed the participation of the army in the Remembrance Day celebrations organised by the British Legion.
In November 1927 Costello married Mary Theresa (‘Molly’; d. December 1984), daughter of Michael F. Kennedy and Kate Kennedy (née Conmee) of Roscommon. They had eight sons and a daughter and lived at Victoria Road, Clontarf. Lieutenant-Commander Rory Costello was his nephew. Costello died 20 October 1986 at Jervis Hospital, Dublin, following a heart attack. His papers are deposited in the Military Archives, Cathal Brugha Barracks, Dublin.