During the Irish War of Independence, Corvin was based in Galway, then, in 1920, he returned to Belfast, where he became quartermaster of the third northern division of the Irish Republican Army (IRA).[1] An opponent of the Anglo-Irish Treaty, he became the IRA's Belfast secretary in 1923.[3] Still working for the Inland Revenue, he later claimed that he was working on the returns of Ulster Unionist Party politician Dawson Bates when he was arrested on Bates' orders, later that year.[1] He was interned at Larne, becoming the officer commanding anti-treaty IRA internees there. In April 1924, he was moved to Derry Gaol,[3] during which time he was a leader of the republican internees, alongside Dan Turley.[4] While inside, he stood for Sinn Féin in Belfast North at the 1924 general election, but took only 3.4% of the votes cast,[5] the party's worst result at the election.[6]
Corvin was released on Christmas Eve 1924,[3] at which time the northern IRA was reorganised; he became the first Officer Commanding its new Belfast Brigade. He had been able to complete his accountancy qualification while interned and founded his own company, later known as Corvin & Co.[1] In 1926, he stood down from his IRA positions, to focus on his business interests.
Corvin served as Eamon Donnelly's election agent in his campaign for Belfast Falls at a 1942 by-election to the Northern Ireland House of Commons.[1] Donnelly won the seat, and his supporters then nominated Corvin for the British House of Commons at the 1943 Belfast West by-election, although the IRA repudiated his candidacy.[10][11] He took only 2.9% of the vote and a distant fourth place in the contest.[5] Despite this, he remained close to some IRA members, and during World War II, he organised the Green Cross Fund to assist the families of republican internees.[1] In 1946, he acted as a pall bearer at the funeral of Seán McCaughey, the last person to die on hunger strike in independent Ireland.[12]
Corvin's son, Donal, became a well known DJ and pop music journalist.[13][2]