Japanese scholar reveals new evidence of Japanese military's human experiments on own troops

During the War of Aggression against China, army surgeons from the Imperial Japanese Army Medical School conducted coercive human experiments on hospitalized Japanese soldiers suffering from mental illnesses by deliberately infecting them with malaria, Kyodo News reported on Monday, citing newly disclosed historical documents.

The findings, revealed by Seiya Matsuno, a historian and researcher at the International Peace Research Institute of Meiji Gakuin University, uncover a lesser-known chapter of wartime history. The findings demonstrate that human experimentation by the Imperial Japanese military was not limited to foreign prisoners of war but extended to Japan's own troops.

According to a paper published in the journal of the Japanese Army Surgeon Corps, the experiment took place in 1940 at the Konodai Army Hospital in Japan's Chiba Prefecture. Its stated aim was to evaluate strategies to prevent troops infected on the Chinese battlefield from spreading malaria upon returning to Japan.

During the study, researchers allowed mosquitoes to feed on the blood of soldiers who had contracted malaria in China. The infected insects were then used to bite 10 Japanese patients hospitalized with schizophrenia and other mental disorders. Five of the subjects subsequently developed acute symptoms after an incubation period, suffering from fevers exceeding 40 degrees Celsius, severe headaches, body aches and loss of appetite.

The records also revealed that Shiro Ishii – then head of the epidemic prevention research laboratory at the Army Medical School and later the leader of the Kwantung Army Epidemic Prevention and Water Purification Department, known as Unit 731 – was involved in directing the experiment.

Matsuno noted that while other military surgeons had also conducted human trials on mentally ill troops, the 1940 case stands as the earliest verified instance to date.

He emphasized the severe ethical violations of the procedures, noting that the subjects' psychiatric conditions left them unable to comprehend the nature or risks of the trial.

Focusing on the fact that the subjects were their own troops rather than prisoners of war reveals a ruthless mindset where nationality was irrelevant, Matsuno noted, adding that the military treated individuals incapable of contributing to the war effort merely as "research material" – an ideology directly aligned with the atrocities later committed by Unit 731. 

(With contributions from agencies)