This article examines Roger Fisher's scholarship in international law in the decades prior to the publication of Getting to Yes. Fisher engaged with the same major questions as other international law scholars during the Cold War, but his scholarship was distinguished by the degree to which he grappled with the cutting-edge social science of the mid-century. Even as Fisher collaborated with game theorists and nuclear strategists to understand the theory of conflict, he maintained a critical view of the basic assumptions of game theoretic analysis – defending certain normative elements of the methodology even as he denied its descriptive claims. Subsequent work sought to generate robust descriptions of the role of law in international decision-making during crises. Fisher's normative and descriptive studies of the role of law in such crises led directly to Getting to Yes, creating a body of ‘meta-game theory’ that situated formal studies of conflict within a lawyer's understanding of dispute resolution. Fisher's engagement with social scientists helps illuminate current methodological debates in international law by highlighting the stakes of these theoretical questions and the tensions between scholarship and practice in international law.