A biological arsenal was developed in Japan between 1919 and 1945. Since 1932, a network of bacteriological and chemical warfare units was until the end of the war responsible for countless medical and scientific atrocities and human experiments. The origins of this armament program, however, go back to the 1880s. What were the scientific and ideological requirements at work behind the institutionalization of such a project? What have then become the protagonists of this science? This dissertation aims to show how, after 1945, the majority of the participants managed to disappear, and why the most prominent scientists were able to reinvent themselves as research pioneers, completely devoid of remorse. However, in the post-war era, some voices started to make themselves heard. Those diffused but continuous narratives gradually led the Japanese population to discover what types of experiments were performed. Sources and documents used here are multiple: military archives, scientific and medical reports, works of historians, popular and documentary novels and testimonies in order to show the diversity of the voices that tell the story of Japanese biological warfare.