Question: Denis O'Brien was a veteran of what conflict that led to the establishment of the Irish Free State?
Sentence (from "Irish Civil War"): The Irish Civil War (Irish: "Cogadh Cathartha na hÉireann" ; 28 June 1922 – 24 May 1923) was a conflict that followed the Irish War of Independence and accompanied the establishment of the Irish Free State, an entity independent from the United Kingdom but within the British Empire.
Relevant evidence: Yes