Exporting nuclear secrecy. The transatlantic diffusion of nuclear secrecy practices in the postwar period (1945-1953)

This article examines how United States (US) nuclear secrecy standards shaped the domestic nuclear policies of Western European states between 1945 and the launch of Atoms for Peace. Focusing on the United Kingdom (UK), Sweden and France, it argues that the spread of nuclear secrecy in Europe cannot be explained solely by domestic dynamics but also resulted from international power asymmetries that structured an emerging economy of nuclear secrecy.Drawing on policy diffusion theory, the article identifies two mechanisms through which US secrecy norms diffused to partner states: coercion and imitation. Coercion operated through conditional access to valued resources—scientific information, technology, and political cooperation—when European practices were deemed incompatible with US containment priorities. Imitation, by contrast, reflected European policymakers’ efforts to conform to what they perceived as appropriate behaviour within an asymmetric relationship, adopting stricter secrecy practices to signal reliability and secure future cooperation. Based on archival evidence, the article shows how US expectations reshaped European information-control regimes, demonstrating how international power relations can produce domestic secrecy practices. In doing so, it highlights the central role of diffusion mechanisms in early nuclear ordering efforts.