The aim of this article is to study discussions within the International Metalworkers’ Federation (IMF) about the early postwar process of European integrationat the intersection of international cooperation and nationally defined interests. The central question is the future of the Ruhr. This article argues that the developing Cold War, and the conflict between social democrats and communists, limited the reach of international trade-union cooperation but simultaneously strengthened the perceived need among social-democratic trade unionists in Western Europe to coordinate their policiesin relation to supposed enemies. European integration in combination with the Cold War also highlighted a need to coordinate the resources of European and anti-communist trade unions in North America. The article shows that the IMF generally supported European integration as a defence against the hypothetical threat from the East, but made attempts to sway the process to include a pronounced social dimension.