Ryoichi Naito file photo [28576]

Ryoichi Naito

Given NameRyoichi


ww2dbaseLieutenant Colonel Ryoichi Naito, a medical doctor specializing in microbiology, was a high ranking officer with the Epidemic Prevention and Water Purification Department (Unit 731) of the Japanese Army. In the 1930s and early 1940s, he operated in northeastern China, where he participated in programs involving pathogen weaponization and human experimentation. In mid-1942, he was made the second scientific head of OKA 9420 headquartered in Outram Park, Singapore (now the building hosting the Singapore Ministry of Health). Under his leadership, OKA 9420 spread to additional sites in Malaya (Permai Hospital in Tampoi, Johor, and a school in Kuala Pilah, Negeri Sembilan), employing about 150 physicians. His primary task was to prevent the spread of tropical diseases among Japanese military personnel; his team also ventured on side projects such as the creation of an anti-tetanus vaccine. Secretly, he also operated a major laboratory operation that cultivated pathogens such as bubonic plague, cholera, smallpox, malaria, typhus, dysentery, and anthrax. Under his direction, tens of thousands rats were trapped locally and brought in from abroad. These rats were injected with diseases and then fed to fleas; the fleas would then be used directly as weapons. The operation fled Singapore in Jun 1945 to Laos, far ahead of a possible British return. Naito was among the Unit 731 officers who were granted immunity by the Americans after the war, in exchange of the knowledge obtained through inhumane methods that the Americans could not conduct. He went on to have a successful career, cofounding the firm Japan Blood Bank (now the pharmaceutical firm Green Cross Corporation) in 1950; some of the fellow cofounders were also former members of Unit 731. He passed away in Jul 1982. In 1998, it was discovered that he had lied to the American occupation, saying that Unit 731 had never used humans in experiments.

ww2dbaseSources: "BiblioAsia", Singapore National Library Board

Last Major Revision: Jun 2019

Ryoichi Naito Timeline

15 Jun 1945 The Japanese OKA 9420 pathogen research facility at the Permai Hospital in Tampoi, Johor, Malaya was disbanded. The personnel was relocated to the main OKA 9420 laboratory in Outram Park, Singapore.
24 Jun 1945 The Japanese OKA 9420 pathogen research operation was relocated from Singapore to Laos. All documents that remained behind were burned.

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Visitor Submitted Comments

1. Anonymous says:
27 Jun 2019 12:31:11 AM

Isn’t he the 9420 band in Singapore manufacturing fleas carrying bubonic plague during ww2?

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