Mallin, Michael Thomas (1874–1916), trade unionist and revolutionary, was born on 1 December 1874 at Ward's Hill in the Liberties in Dublin, the eldest of six surviving children (four boys and two girls) of John Mallin, a boatwright and carpenter, and his wife Sarah (née Dowling), a silk winder. He was educated at Denmark Street national school, Dublin, and on 21 October 1889 joined the Royal Scots Fusiliers (in which his uncle James Dowling was a pay sergeant) as a drummer boy, enlisting for twelve years, and was stationed at the Curragh. On 1 June 1891 he was promoted to drummer (the rank he held throughout his service); as part of his training he learned the flute and violin and studied music theory. He also became a useful lightweight boxer and the best shot in his company. In 1896 his battalion went to India, where he served for six years. He took part in the Tirah campaign (1897–8) against insurgent tribes on the north-west frontier and contracted malaria, from which he suffered sporadically for the rest of his life. While serving in India, Mallin became disillusioned with military life and sympathetic to the Indian struggle for independence. In a letter home he recorded his wish that 'it was for Erin that I was fighting and not against these poor people' (Hughes, 36). He longed for his discharge from the army, which finally came on 18 December 1902. On 26 April 1903 he married Agnes Hickey of Chapelizod, Co. Dublin. They had met in Dublin nine years earlier and corresponded throughout his service overseas.
Mallin was apprenticed as a silk weaver at Atkinson's poplin factory in Dublin and by 1908 had become a qualified weaver and secretary of the Silk Weavers' Union. Active in socialist politics, he was a member of a unity committee formed to bring together opposing elements of the Irish socialist movement, which led to the founding of the Socialist Party of Ireland in August 1909. Mallin was secretary of the Silk Weavers' Union during a bitter four-month strike (March to June 1913) and wrote accounts of the dispute for the Irish Worker. After the strike he was forced out of Atkinson's and tried various ways to earn a living: opening a newsagent's shop, starting a chicken farm and running a cinema, all of which proved unsuccessful. He supplemented his income by teaching music to local children and won several medals for conducting bands such as the Dublin Fife and Drum Band (1913–14). In May 1914 he took over the ITGWU's Emmet Fife and Drum Band and became a member of the union, moving his family to Emmet Hall, headquarters of the union's Inchicore branch. When James Connolly (qv) took command of the Irish Citizen Army in October 1914 he appointed Mallin his chief-of-staff. Mallin, a devout catholic and temperance advocate with a passion for music and books (especially ancient history and the novels of Joseph Conrad), was a popular and respected figure among his comrades. Although gentle and soft-spoken, he had a firm side to his character and insisted on strict discipline. Connolly had a high opinion of his abilities and left the business of organising and training the force largely to him. Mallin put his military experience to good use in welding the Citizen Army into a disciplined and well-drilled unit, leading it on outdoor manoeuvres including mock attacks on public buildings and performing well in drill contests against the Irish Volunteers. As an ex-soldier, he was adept in obtaining arms and ammunition from serving soldiers to equip the Citizen Army. He also wrote articles on guerrilla warfare derived from his experience in India which were published in the Workers' Republic from August 1915.
In April 1916, on the Saturday prior to the Easter rising, Mallin was given the Irish Volunteer rank of commandant, and appears to have known of the plan weeks in advance. On Easter Sunday evening his instrumental quartet, known as the 'Workers' Orchestra', in which he played the flute, held an improvised concert for Citizen Army members in Liberty Hall. He led the Citizen Army force that occupied St Stephen's Green on Monday 24 April, digging trenches in the park and erecting barricades on the surrounding roads; he appointed Constance Markievicz (qv) as his second-in-command. As dawn broke on Tuesday they came under fire from a machine gun on the roof of the Shelbourne hotel, suffering several casualties. Mallin himself had to drag a wounded man to safety and had a close shave when a bullet went through the brim of his hat. He was forced to withdraw to the College of Surgeons on the west side of the Green, a safer position but one of little strategic value. The decision to occupy a park overlooked on all sides by high buildings was a serious mistake, as was the failure to seize the Shelbourne, which dominated the area. Over the next few days Mallin ordered sporadic attacks on nearby British army positions, but his force was out-manned and out-gunned and their isolated forays had little effect. Having received Connolly's confirmation of the order to lay down arms, Mallin surrendered along with his garrison of 109 men and 10 women on 30 April. He was tried by court martial in Richmond barracks on 5 May. As a senior figure in the Citizen Army and head of an independent command that had inflicted casualties on crown forces, he was regarded as a leader and sentenced to death. His anguish at leaving his pregnant wife and four young children was clearly evident in a letter written to Agnes on the eve of his execution. He was shot by firing squad in Kilmainham jail on 8 May 1916 and buried at Arbour Hill.
His fifth child, Mary Constance (1916–2005), was born four months after his death. His wife struggled to raise the young family and died of tuberculosis in 1932. In his last letter to his wife Mallin had expressed the wish that his two youngest children should enter religious life: his son Joseph Michael (1913–2018) became a Jesuit priest and his daughter Una (1908–89) a Loreto sister; another son, Seán (1906–77), also became a Jesuit. His eldest son Séamus (qv) became an engineer and chairman of Bord Iascaigh Mhara (1952–62).