Almost no historian of the Second World War nowadays fails to acknowledge the important role of signals intelligence (SIGINT). By contrast, most histories of postwar international relations omit – without explanation – all reference to SIGINT. Neglect of this and other aspects of intelligence has significantly distorted the study of the Cold War. A new generation of scholars, however, has begun to challenge this neglect. The article seeks to show how recent research on intelligence is changing our understanding of the early Cold War.