Amidst the shifting world order and an uncertain geopolitics surrounding the East Asia in the 1940s, the notion of population became subject to reinterpretation, and the overpopulation of racialized and monolithic “East Asians” became problematized as it was considered to be jeopardizing global security. Specifically, pressed by the cold war exigencies of containment and American hegemony, white American commentators alarmed that social and economic chaos caused by overpopulation would make East Asia to succumb to Communism. In response, the Japanese government – still under the US occupation – quickly enacted birth control policies while the occupation authorities condoned the resurgence of birth control movement that had hitherto been suppressed due to its association with socialism.

In this context, leading demographers from the US and Japan began to conduct projects in order to understand the demographic trend of Japan and to test for the efficacy of certain contraceptives and the local birth control service within Japan. These projects, though seemingly independent from each other, were generally a result of cumulative interactions between American and Japanese advocates who, informed by the burgeoning cold war biopolitics, problematized the reproductive habit of certain segments of Japanese people; namely, the rural population, urban poor, and coal miners whose wives were relying on the company health insurance to have abortions. The presentation then analyzes a) ideas of race and class interwoven with the cold war politics, which undergirded the scientific projects as well as the US-Japan interactions within the projects, b) the role of the Japanese government and American philanthropists, most notably Clarence Gamble and the Rockefeller Foundation, in fostering scientific cooperation across the Pacific, and c) the significance of these elements for the formation of scientific knowledge on the population of Japan as well as for the shaping of images in the international scientific community regarding the reproductive habits of Japanese people.