Born near Donohill in County Tipperary, Dan Breen became involved in the Irish Volunteers and the Irish Republican Brotherhood before the struggle for independence intensified. On 21 January 1919, he took part in the Soloheadbeg ambush, an event widely regarded as marking the beginning of the War of Independence. Breen spent much of the conflict on the run and later recounted his experiences in My Fight for Irish Freedom. He opposed the Anglo-Irish Treaty and fought on the anti-Treaty side during the Civil War. In later years, he entered politics as a Fianna Fáil representative, carrying his revolutionary past into the political life of the new state.