Abstract: This essay offers a theory of atrocity propaganda and surveys strategies for countering it. I first review examples of atrocity propaganda disseminated before, during, and after WWI. I then explain how the linguistic tactic of persuasive definition makes it difficult to confirm, or rebut, reports of atrocities. Although both International Criminal Law and International Human Rights Law restrict willfully false stories of enemy misdeeds, these restrictions don’t solve the core problem of distinguishing legitimate and illegitimate reports of atrocities. The essay concludes by outlining steps that can mitigate, but not eliminate, the threat posed by this distinctive form of propaganda.