This article provides a systematic examination of the role of security considerations in shaping mass preferences over international economic exchange. The authors employ multiple survey experiments conducted in the United States and India, along with observational and case study evidence, to investigate how geopolitics affects voters’ views of international trade. Their research shows that respondents consistently—and by large margins—prefer trading with allies over adversaries. Negative prior beliefs about adversaries, amplified by concerns that trade will bolster the partner's military, account for this preference. Yet the authors also find that a significant proportion of the public believes that trade can lead to peace and that the peace-inducing aspects of trade can cause voters to overcome their aversion to trade with adversaries. This article helps explain when and why governments constrained by public opinion pursue economic cooperation in the shadow of conflict.