Although identified above all with the French Confédération Général du Travail prior to the First World War, revolutionary syndicalism had become an international movement by 1914, when various labour organizations in Europe, North and South America, and Australasia espoused its doctrines or the kindred doctrines of industrial unionism. The desire to establish durable international bonds between these revolutionary organizations had grown steadily, especially in Europe, where by 1912 organized syndicalist bodies existed in France, Holland, Germany, Sweden, Denmark, Britain, Belgium, Spain and Italy. The congress held in London in the autumn of 1913 represented the first effort to create a vehicle of syndicalist internationalism. But the congress and the debate surrounding it demonstrated not only that syndicalists were not in accord on international tactics, nor on national tactics, but also that the deepest cleavage on the question of international strategy was that dividing the CGT from most syndicalist organizations in other countries.

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.

In December 1918, in its first conference since the outbreak of the Great War, the revolutionary syndicalist Free Association of German Trade Unions (Freie Vereinigung deutscher Gewerkschaften — FVdG) noted that it was the only trade union organization in the country that did not have to readjust its program with the return of peace. The syndicalists were alluding to the fact that theirs had been the only German workers' organization to have adopted an internationalist rather than a patriotic response to the war. The FVdG had neither supported the national cause nor endorsed the Burgfrieden, or civil truce, whereby all factional disputes were to be set aside and all sectoral interests subordinated to the higher interests of the imperiled nation. Its opposition to the war, its refusal to cooperate with the state and the employers, moreover, had made the FVdG a beneficiary of the growing radicalization of German workers. In the immediate postwar period it expanded at a rate six times greater than any other labor organization in the country.