One of the fabled ‘Sydney Twelve’, imprisoned for their opposition to war and conscription in 1916, Tom Glynn (1881–1934) was the founding editor of Direct Action, the periodical of the Australian ‘Administration’ of the American-based movement, the Industrial Workers of the World (IWW). Born in Galway, Ireland, and immigrating to Melbourne as a teenager, Glynn came into contact with IWW ideology while involved in labour struggles in South Africa. Deepening his commitment during a sojourn in the United States and Canada, he returned to Australia in 1912 to build the movement there. In August 1914, Direct Action was the most trenchant opponent of war in the country, and Glynn’s journalism and editorship were critical to that opposition. This article examines Glynn’s wartime writings, focusing in particular on his advocacy of sabotage, and on how that led to his imprisonment and to the suppression of the IWW in Australia.