This movement organised the largest body of anarchists in world history: the anarcho-syndicalist National Confederation of Labour (CNT). Anarchist cultural practices became ingrained in localities across the whole of Spain, laying foundations which maintained the movement's popular support until the end of the Spanish Civil War in 1939. This book shows that grassroots print culture was central to these developments: driving the development of ideology and strategy and providing an informal structure to a movement that shunned recognised leadership and bureaucracy. It offers a rich analysis of the cultural foundations of Spanish anarchism, while challenging claims that the movement was exceptional or peculiar in its formation, by situating it alongside other decentrali sed, bottom-up mobilisations across historical and contemporary contexts.