Unit 731

Unit 731 was an Imperial Japanese Army research and development facility for biological weapons, headquartered in Pingfan, Manchuria. It was headed by Gen. Shiro Ishii, who was given immunity from war crimes prosecution in exchange for his experimental data.

It engaged in human experimentation and field use of weapons.

Technology

In comparison with the contemporaneous U.S. and British programs, the Japanese methods for distributing infectious agents was relatively primitive. Interestingly, however, some of the devices alleged to be U.S. biological munitions, in the Korean War, had a significant resemblance to Unit 731 devices. The Soviets did capture some Unit 731 personnel, and that information may have made its way to North Korea.

When a disease was vector-borne, such as plague carried by fleas, the Japanese approach was to distribute infected arthropods, rather than the more difficult process of forming an aerosol spray. Anthrax was first delivered on bullets or bomb fragments

Diseases being studied included:

• plague
• cholera
• typhus
• anthrax
• glanders

U.S. evaluation

U.S. intelligence first obtained fragmentary knowledge of Unit 731 in December 1944, with more details in April 1945. After the surrender of Japan, a U.S. Army microbiologist, was sent to interrogate persons in the program and evaluate documents.

Two separate organizations were involved in the intelligence interrogations and document examinations: the Chemical Warfare Service, which provided the technical expertise, and the G-2 Division of Douglas MacArthur's staff, headed by Major General Charles Willoughby.

Relatively recently declassified documents have suggested that G-2 may have exaggerated the unquestionable atrocities, possibly to obtain more funding. They also showed direct cash payments to Ishii and others, as well as immunity to war crimes prosecution.