The historiography of the Cold War has witnessed a revived interest in non-material factors such as culture and ideology. Although this incipient cultural history of the Cold War has focused mainly on the period from 1945 until the early 1960s, the signing of the Helsinki Final Act in 1975 turned ideas into potent factors of international politics when East European opposition groups began to expose how their governments violated the accord's human rights provisions. By putting the emergence of one such opposition group, the Polish Workers' Defense Committee, in an international context, this article extends Cold War cultural history into the 1970s and 1980s, tracing how human rights ideas affected international and domestic politics. The Communist states' willingness to put up with the human rights provisions in the Helsinki Final Act was not sufficient to "shame" them internationally. Instead, what happened is that Western leftists, after encountering East European dissidents, increasingly perceived human rights as a precondition for the success of their own political project and hence revoked what Robert Horvath calls the "revolutionary privilege" long granted to Communist regimes. Because Communism's identity was so closely related to its struggle with the West, this criticism was particularly damaging. Only within the dynamics of a cultural framework from earlier stages of postwar history did transnational human rights advocacy become effective.