Thomas Curtin is born at Ballyknockane, Mourne Abbey, County Cork, on March 20, 1884, the son of Patrick Curtin, a farmer, and Julia Sheehan. He attends Burnfort National School. In 1897 the family moves to Cork City, where he attends the North Monastery school.
Mac Curtain, as he later becomes known, is active in a number of cultural and political movements beginning around the turn of the 20th century. He joins the Blackpool, Cork branch of Conradh na Gaeilge, becoming its secretary in 1902. He has interests in music, poetry, history, archaeology and Irish history. He works in his early career as a clerk, and in his free time teaches Irish. In 1911 he joins Fianna Éireann, and is a member of the Irish Volunteers.
He meets Elizabeth Walsh (Eibhlís Breathnach) at a Gaelic League meeting and they marry on June 28, 1908. They have six children, five of whom survive into adulthood. The family lives over 40 Thomas Davis Street, where Mac Curtain runs a small clothing and rainwear factory.
In April 1916, at the outset of the Easter Rising, Mac Curtain commands a force of up to 1,000 men of the Irish Volunteers who assemble at various locations around County Cork. From the volunteers headquarters at Sheares Street in the city, Mac Curtain and his officers await orders from the volunteer leadership in Dublin but conflicting instructions and confusion prevail and as a result the Cork volunteers never enter the fray. A tense stand-off develops when British forces surround the volunteer hall and continued for a week until a negotiated agreement leads to the surrender of the volunteers’ arms to the then Lord Mayor of Cork Thomas Butterfield on the understanding that they will be returned at a later date. This does not happen however and Mac Curtain is jailed in Wakefield Prison, in the Frongoch internment camp in Wales, and in Reading Gaol. After the general amnesty of participants in the Rising 18 months later, Mac Curtain returns to active duty as a Commandant of what is now the Irish Republican Army.
By 1918 Mac Curtain is a brigade commander, the highest and most important rank in the IRA. During the Conscription Crisis of 1918, he actively encourages the hiring of the women of Cumann na mBan to cater for Volunteers. He is personally involved with Michael Collins‘ The Squad that, along with a Cork battalion, attempt to assassinate Lord John French, whose car is missed as the convoy passes through the ambush positions. Despite the setback he remains brigadier of No.1 Cork when he is elected Lord Mayor. He is elected in the January 1920 council elections as the Sinn Féin councillor for NW Ward No. 3 of Cork, and is chosen by his fellow councillors to be the Lord Mayor. He begins a process of political reform within the city.
In January 1919, the Irish War of Independence starts and Mac Curtain becomes an officer in the IRA. On March 20, 1920, his 36th birthday, Mac Curtain is shot dead in front of his wife and son by a group of men with blackened faces, who are found to be members of the Auxilaries along with unknown members of the Royal Irish Constabulary (RIC) by the official inquest into the event. In the wake of the killing, which is in revenge for the shooting of a policeman, Mac Curtain’s house in Blackpool is ransacked.
The killing causes widespread public outrage. The coroner’s inquest passes a verdict of willful murder against British Prime Minister David Lloyd George and against certain members of the RIC. Michael Collins later orders his squad of assassins to uncover and assassinate the police officers involved in the attack. RIC District Inspector Oswald Swanzy, who had ordered the attack, is fatally shot, with Mac Curtain’s own revolver, while leaving a Protestant church in Lisburn, County Antrim on August 22, 1920, sparking what is described by Tim Pat Coogan as a “pogrom” against the Catholic residents of the town.
Tomás Mac Curtain is buried in St. Finbarr’s Cemetery, Cork.