From 1919 to 1923, Barcelona experienced unprecedented levels of social conflict. The growth of the anarcho-syndicalist National Confederation of Labour (CNT) had awakened the spectre of social revolution among the city's conservative classes, and a broad constellation of reactionary forces lined up against it, the Sindicatos Libres (free trade unions) being the most formidable among them. Created in 1919 by Catholic workers, the Sindicatos Libres were able to capitalize on the exhaustion that had set in among certain working-class groups who had grown wary of reckless strike action. Using violence to fight back against the CNT, the Libres could claim 175,000 members by mid-1922. They mobilized the religious, corporatist, and regionalist sentiments harboured by sectors of the city's workforce and, by adopting a modern repertoire of action, they bypassed the traditional aversion to mass mobilization that had characterized the Catholic labour movement and Spanish conservative parties until then. In many ways, the ideology and tactics of the Libres adumbrated fascism, but their success was short-lived. In late 1922, an upswing in strike action and an abatement of state repression allowed the CNT to recover at the expense of the Libres. This article explores the rise and fall of an organization the study of which has been neglected, situating it in a European context of political polarization whereby the traditional right attempted to modernize its tactics and adapt them to a rising challenge from the revolutionary left. It will also serve as a window through which to examine the complex relationship between workers’ trade union affiliations and their political and cultural identity.