Providing a clear overview of Irish radicalism, this biographical account sheds light on the life and times of Sean McLoughlin, who became Commandant-General of the army of the Irish Republic at the young age of 21. The subject’s history is chronicled, including his survival of the executions by the British Army, how he became an active trade union leader, and his joining with the Communist Party. This reference also illustrates the reactionary times McLoughlin lived in, showing how little support there was for one who combined the visions of a social and national revolution. Rescuing the key players in the Irish revolutionary movement from obscurity, this discussion reveals new and critical insights on the history of the republican and labour movements, the communist left in Ireland and Great Britain, and the role of Irish trade union leader and socialist activist James Larkin.