This article argues that syndicalist trade union organizations, viewed internationally, were unique in First World War Europe in not supporting the war efforts or defensive efforts of their respective governments. The support for the war of the important French organisation has obscured the fact that the remaining five national syndicalist organisations – in belligerent Germany and Italy, and in neutral Spain, Sweden and the Netherlands – remained faithful to their professed workers' internationalism. The article argues that forces tending to integrate the labour movement in pre-1914 Europe had less effect on syndicalists than on other trade unions, and that syndicalist resistance to both integration and war in the non-Gallic countries was also influenced by their rivalry with social-democratic organisations.