More than two dozen U.S. anthropologists worked for the Office of Strategic Services (OSS) during the Second World War. Some anthropologists at the OSS's Research and Analysis Branch analysed information on Japanese culture and tracked shifts in Japanese morale to estimate the best ways of employing psychological warfare. Among the papers produced by these anthropologists was a 1943 'Preliminary Report on Japanese Anthropology' which included the contemplation of biological warfare programmes using anthrax and other weapons of mass destruction on Japanese civilian and military populations. This article summarizes and critiques the roles of American anthropology in designing and opposing various programmes directed against Japanese soldiers and civilians under consideration at the OSS.