Given that the practices and institutions of knowledge production commonly referred to as ‘science’ are believed to have ‘Western’ origins, their apparent proliferation entails negotiations and power dynamics that shape both science and diplomacy in specific locales. This paper investigates a facet of this co-production of science and diplomacy in the emergence of knowledge infrastructure in Japan during the Allied Occupation. It focuses on the 1947 delegation from the United States National Academy of Sciences to Japan and its role in (...) creating the Science Council of Japan (SCJ). While historians view this mission as having been dispatched to provide advice on the foundation of the SCJ, it was in fact an unintentional outcome. The original plan was to recruit long-term scientific advisers on science policy to Douglas MacArthur's headquarters. The creation of the SCJ was not the brainchild of any individual but the result of an unforeseen alteration of the original idea through negotiations among various actors. By examining the transnational aspects of this process and the complex social process underlying it, and drawing on Manuel DeLanda's assemblage theory, this paper proposes the concept of ‘techno-diplomatic assemblage’ for understanding the transnational construction of knowledge infrastructure such as the emergence of the SCJ. (shrink)