A newly released 47-minute testimony from a former member of Imperial Japan’s Unit 731 has reignited documentation that the unit pursued industrial-scale biological weapons and conducted human experimentation during the Second World War. The full interview with former employee Sato Hideo was published for the first time by the Unit 731 Exhibition Hall in China and was recorded by a Japanese scholar (西里扶甬子). Curators say the account stitches together laboratory procedures, mass production methods and the organised use of infected animals as vectors.
Sato describes dissecting more than a thousand small animals — mainly guinea pigs and mice — to study plague pathology and to test growth conditions, and he states plainly that the research aim was to “turn the plague bacterium into a weapon.” He recounts standardized incubation rooms, “culture tanks” and a production regime calibrated to temperatures such as 37°C to multiply pathogens over 24–48 hours. The testimony also outlines how cultured bacteria were placed in bombs for aerial dispersal.
Museum officials and researchers cited by the exhibition corroborate the industrial scale implied by Sato’s account. They reference postwar courtroom testimony from a Unit 731 production manager that alleged monthly outputs of hundreds of kilograms of plague and up to a tonne of anthrax, framing the operation as more than ad hoc experimentation but as a factory-level enterprise. The combination of technical description and claimed yields strengthens the case that biological agents were produced at scale with potential military deployment in mind.
Equally chilling in Sato’s testimony is the admission that human experiments were continuous and organised. He names special prison wards in the unit’s four-square building complex — buildings 7 and 8 — as sites reserved for “experimental subjects” and explains that those chosen were maintained in good physical condition so their reactions would mirror those of healthy battlefield populations. Sato’s description of controlled food and confinement underscores that human beings were treated as research specimens rather than patients.
Curators emphasise that Unit 731 was not a fringe operation but drew heavily on Japan’s medical elite. The exhibition’s director notes the transfer of doctors and students from leading universities — including Tokyo Imperial, Kyoto Imperial and Kyushu — and claims the unit included hundreds of doctorate-level personnel. That institutional depth is central to the argument that biological warfare and live human experimentation were systematic, state-directed crimes rather than the actions of isolated individuals.
The newly public testimony dovetails with extant archival material and physical sites related to Unit 731, and the museum argues the deposit of this firsthand account fills gaps in the evidentiary chain. For international observers, the significance is twofold: it supplies another incriminating primary source authored by a perpetrator, and it underlines the modern stakes of historical accountability and biosecurity. The account also revives debates about postwar handling of Unit 731 records and personnel, including alleged leniency or secrecy tied to Cold War intelligence interests.
The release will have diplomatic resonance. For China, the testimony confirms long-standing claims about Japanese biological operations during the war and will likely reinforce calls for acknowledgement and historical clarity. For Japan and international audiences, it is a reminder of how state-sanctioned medical expertise can be repurposed for atrocity, and why rigorous transparency, archival access and education about past abuses matter for preventing future misuse of biological science.