Tomás Mac Curtain was born at Ballyknockane, Mourne Abbey, County Cork, on 20 March 1884, the son of Patrick Curtin, a farmer, and Julia Sheehan.

[citation needed] In April 1916, at the outset of the Easter Rising, Mac Curtain commanded a force of up to 1,000 men of the Irish Volunteers who assembled at various locations around County Cork.

A tense stand-off developed when British forces surrounded the volunteer hall and it continued for a week until an agreement was negotiated with Captain F. W. Dickie, aide-de-camp to Brigadier General W. F. H. Stafford, the General Officer Commanding (GOC) in Cork,[5][6] led to the surrender of the volunteers' arms to the then Lord Mayor of Cork, Thomas C. Butterfield, on the understanding that they would be returned at a later date.

[7] After the general amnesty of participants in the Rising 18 months later, Mac Curtain returned to active duty a local commandant of what was now the Irish Republican Army in County Cork.

[9] During the Conscription Crisis in the autumn of 1918, Mac Curtain actively encouraged the hiring of the women of Cumann na mBan to cater for Volunteers.

[10] He was personally involved with The Squad that, with a Cork battalion, attempted to assassinate Lord French, whose car was missed as the convoy passed through the ambush positions.

[11] On 20 March 1920, his 36th birthday, Mac Curtain was shot dead,[12] in front of his wife and son, by a group of men with blackened faces, who were found, by the official inquest into the event, to be members of the Royal Irish Constabulary (RIC).

On 22 August 1920, RIC District Inspector Oswald Swanzy, who had ordered the attack, was fatally shot with Mac Curtain's own revolver, while leaving a Protestant church in Lisburn, County Antrim, sparking what was described by Tim Pat Coogan as a "pogrom" against the Catholic residents of the town (see The Troubles in Northern Ireland (1920–1922)).