ABSTRACT This article focuses on the French communist scientists’ attack, executed in 1953, on US initiatives for the promotion of science in Europe. Collated in the anonymous booklet Un plan U.S.A. de mainmise sur la science, these accusations caused a sensation in the already tense political climate of the early 1950s by alleging that American initiatives offered cover to intelligence operations, and a chokehold on the development of European science. While US government agencies never offered an official comment on these indictments, in great secrecy their officials sought to find out about the booklet’s authors, identify potential leaks of restricted information that might have informed its completion, and reorient science initiatives in Europe because of what the communist propaganda exposed. This essay thus argues that US efforts to reduce the impact that the publication had in France (and Western Europe more generally) played a role in shaping American hegemony, since finding ways to deflate the influence of dissenting voices in European science, at times stealthily, was as decisive as consensus building through the strengthening of transatlantic scientific relations.