This text examines the rise of the German Communist Party in the crucial period between the Kapp Putsch and the stabilization of the Weimar Republic. Based on archival research, its reconstruction of Communist participation in union and protest movements in the key industrial region of Rhineland-Westphalia offers a detailed social analysis of Communist support, organization, and political strategy in German labour unions. By viewing German Communism against the backdrop of industrial structures and economic conditions, this study illuminates the deeper divisions in the German workers' movement that contributed to the tragedy of the Weimar Republic.