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.

The program was always under the cover identity of a water purification laboratory, where Ishii had indeed done significant development. Ishii's first facility, built in 1932, was the Zhoghma Fortress, a prison on the outskirts of Harbin. After an escape in 1935, they moved closer to Harbin at Pingfang. Unit 731 also had a number of field subunits and specialized laboratories at other locations.

Authorized by an Imperial order, it was visited by Prince Chichibu.

It engaged in human experimentation and field use of weapons.

Experimentation

Human experimentation, completely involuntary and in violation of the principles of the Nuremberg Code and the Declaration of Helsinki, was not limited to biological weapons. It also included experiments in conditions of freezing, extreme heat, and exhaustion; surgical procedures on living subjects without anesthesia; poisoning; and bullet and grenade tests. Some very similar experiments resulted in death sentences for Nazi experimenters at the Medical Case at the Nuremberg Military Tribunals

Most of the victims were Chinese, dehumanized as maruta or "logs" by the staff.

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 initial 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. Plague was also delivered by rats in porcelain containers dropped by parachute.

Diseases being studied included:

• plague
• cholera
• typhus
• anthrax
• glanders
• typhoid fever
• unspecified hemorrhagic fever

Field operations

The first attack was believed to be against Soviet troops in 1939, involving typhoid fever being poured into water supplies.

Later, aerosol attacks were used, which also caused Japanese casualties.

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.