This new biography explores the neglected life and political career of Sean Murray, who went from an unremarkable, rural, northern Catholic upbringing to General Secretary of the Communist Party of Ireland, and was one of the most prominent left-wing thinkers of his era. An Irish War of Independence volunteer, anti-Treaty republican, and graduate of the International Lenin School in Moscow, Murray rooted himself in the key Irish labor, republican, and international struggles of his time. Using previously untapped sources, the book uncovers the details of Murray's IRA activities during the Irish revolutionary period, his significant contribution to the 1932 outdoor relief strike and the short-lived Republican Congress initiative, and his crucial role in organizing the Irish contingent of the International Brigades in the Spanish Civil War. Shining a spotlight on Murray's close personal and political relationships with Peadar O'Donnell, Frank Ryan, Jim Larkin Jr., Hanna Sheehy Skeffington, and many others, the book reveals how cross-pollination between the Irish socialist and left republican movements was maintained by virtue of these relationships. This is a story of how, in the face of adversity (the coercive measures of the Unionist state and ''red scare'' tactics of Catholic Ireland) Sean Murray left a significant imprint on Irish leftist politics through his work as an activist and organizer, a prolific writer, a propagandist, and a theorist. [Subject: Biography, Irish Studies, Political History]