This paper argues that the ferocity of the campaign against Zahn stemmed from the tight links between politics, religion and the process of working through the recent past in Germany. The debates surrounding Zahn’s controversial theses emerged as a referendum not only on the role of religion in politics but on the support of leading Catholic politicians and clergy for Germany’s rearmament efforts. In carrying out his research on Catholic peace-movements during a Fulbright year in Germany, Zahn tapped into a loose grouping of Catholic nonconformists, “peacemongers” and opponents of Adenauer’s regime. Though members of the network against Zahn succeeded in temporarily derailing publication of his book in the United States and Germany, their measures ultimately backfired, transforming the debates about the Catholic past into a discussion of tolerance in a democratic society. The battle for the Catholic past centered on how to position German Catholicism in a modern, democratic society. This paper is based on more than two years of research in fifty archives in six countries.