Drawing upon a vast array of primary sources, this article focuses on a key period of modern Spanish history: November 1918 – April 1919. In the aftermath of the First World War and spurred on by the Allied victory, demands by Catalonia's political elites for greater autonomy seized the country's agenda. However, the political tussle between the centre and the Catalan elites ended a few months later with their mutual defeat. The upsurge of labour agitation and the hopes of the proletariat generated by the Bolshevik Revolution combined with bourgeois fear resulted in the question of national identity being superseded by bitter class conflict. This article conveys the thesis that these crucial months crystallized the organic crisis of the ruling liberal regime. Indeed, the outcome of these events proved its fragile foundations, dashed hopes for a reformist and negotiated solution, and constituted a dress rehearsal for the military coup of 1923, a clear example of the reactionary backlash which swept across Europe in the interwar years.