Throughout the twentieth century, American conceptions of rights bore marks of Reconstruction, the Founding, and even earlier periods of history. Around the time of World War II, however, a new set of substantive political commitments reshaped both the form and the content of American rights. Once again, the transformation of rights discourse followed the pattern of adversity, reaction, and synthesis. The chief adversities this time stemmed from Nazi Germany and the Soviet Union. For a generation of mid-century Americans, the conflict with those two powers shaped politics and ideology. Sometimes, Americans collapsed the Nazi and Soviet threats into a single concept under the name of “totalitarianism.” According to many American intellectuals from Hannah Arendt to Arthur Schlesinger, the obvious differences between the Nazi and Soviet orders were in fact less significant than their essential similarities, and it therefore made sense to see opposition to Germany and the Soviet Union as one struggle rather than two. Whether American reactions against Nazi and Soviet adversity should be counted as one phenomenon or two is a question without an overarching answer: anti-Nazism and anti-Sovietism merged in some respects but not in others. No matter whether conceived as one project or two, however, the cumulative American reaction against European totalitarianism became so powerful a force in the world of legal and political ideas that it sometimes surpassed, though without ever completely eclipsing, the influences of the ideas and experiences of older eras.