From its inception in the late 1940s the communist-led peace movement quickly grew into a global network of peace organisations and activists. Its congresses attracted thousands of delegates and the support of a dazzling array of scientists, artists and intellectuals. Hundreds of millions of people signed its anti-nuclear petitions. The story of the communist peace movement is a neglected page in cold war history. It is the story of the rise and fall of a powerful movement that created a template for postwar transnational peace campaigning. Its history exemplifies the utility of soft power and the role of transnational movements in helping to shape not just international relations but the foreign policy identities of diverse societies. The communist peace movement did not succeed in ending the cold war but it did help ameliorate it, not least by its impact on the societal politics of the USSR. Based on findings from American, Belgium, British, Finnish, French, Hungarian, Italian, and Russian archives, this project explores the history of the postwar communist peace movement through the role of Its key core leaders: J.D. Bernal, Isabelle Blume, Pierre Cot, Ilya Ehrenburg, Frédéric Joliot-Curie and Pietro Nenni.