Between 1932 and 1945 scientists and doctors with the Imperial Japanese Army conducted thousands of medical experiments on human beings.  This testing program surpassed in scale, extent, and duration that of Nazi doctors in German-occupied Europe.  More importantly, these experiments also included a biological weapons testing program, which even the Germans never attempted.  These activities took place in a series of research camps established in the Japanese puppet-state of Manchukuo (Manchuria), which Japan had conquered from China in 1931.  The subjects of the testing included civilians and prisoners of war, among which were Chinese, Koreans, Russians, Mongolians, Americans, and POWs from other Allied countries.  Symbolic of their disdain for human life, the Japanese referred to these testing subjects as "Maruta" or "logs".

The primary testing facility was located in a camp complex at Ping Fan outside of the city of Harbin.  The unit stationed there was designated Unit 731 and placed under the command of Lieutenant General Ishii Shiro.  For security purposes Unit 731 was given the ironic designation of "Water Purification Unit 731".  In the last two decades the designation "Unit 731" has become a blanket term used to describe the overall Japanese bio-weapons program.  In reality, however, the complex under Unit 731 consisted of more than 150 buildings spread out over six kilometers.  In addition, nine satellite facilities were also established: Unit 100, Unit 200, Unite 516, Unit 543, Unit 773, Unit 1644, Unit 1855, Unit 8604, and Unit 9420.

Within the Unit 731 complex numerous factories and laboratories produced chemicals and biological agents, among which were disease-infected fleas and plague bacteria.  Autopsies and other controlled experiments were carried out as well.  These included, but were not limited to

  • The testing of grenades, flame throwers, and bombs on human beings.
  • The removal of entire bodily organs purposely infected with various diseases in order to see the effect of the disease on the organ.
  • Amputations of limbs for studying the impact of blood loss.
  • Frostbite experiments.
  • Operations on subjects in which parts of organs would be removed , limbs would be moved around on the body, and healthy organs would be removed to study the reaction of the body.
  • Food and water deprivation to study the effect and duration before death.
  • Air pressure experiments in which subjects died.
  • Burning experiments to determine the physiological effect of fire on the human body.
  • X-ray radiation experiments
  • Combining animal and human blood experiments.
  • Simulated stroke experiments using air bubbles.

A large number of biological weapons experiments were also conducted at Ping Fan and its subsidiary camps.  These experiments sometimes entailed the injection of a biological pathogen into the body of a human subject.  Among the pathogens tested were cholera, small pox, plague, and botulism.  Once the disease had run its course an autopsy would be conducted to determine the impact of the pathogen.  Other experiments included placing humans in gas chambers and exposing them to airborne diseases like anthrax.  Just under 1,000 autopsies were carried out at Unit 731, with estimates of the overall number who being as high as 3,000 people.

In addition to conducting medical experiments in controlled camp conditions, the Japanese also conducted field tests.  These tests took place during the Second Sino-Japanese war from 1937 to 1945 and they entailed the use of weaponized pathogens.  Parachute-laden ceramic bombs containing plague-infected fleas were dropped on Chinese cities and water supplies were poisoned with water-borne pathogens like cholera.  Altogether the Japanese attacked eleven Chinese cities with biological weapons, causing the deaths of as many as 200,000 people.  This research, while deemed important by the Japanese High Command, likely did not significantly alter the course of the war in China.  Furthermore, during the last two years of the conflict with the United States, General Ishii unsuccessfully lobbied for the use of biological weapons in the Pacific.

Toward the end of the war the activities of Unit 731 were gradually curtailed.  Then, shortly before the Japanese surrender, Ishii swore his personnel to silence and ordered the Ping Fan complex destroyed.  During these final operations Japanese troops released thousands of plague-infected rodents and other disease-infected animals.  The resulting outbreaks of the plague killed at least 30,000 people in the Harbin area from 1946 through 1948.  Tons of toxic chemicals were also dumped into rivers or buried.  Most of the buildings at Ping Fan were then either razed to the ground or destroyed with explosives.



Following Japan's surrender to the Allies in August 1945, General Douglas MacArthur became the Supreme Commander of the Allied Powers.  His office in Tokyo opened officially in September 1945 and was charged with rebuilding Japan during the American occupation.  Within weeks after MacArthur's arrival, Lt. Colonel Murray Sanders from Ft. Detrick, MD, was assigned the task of investigating rumors about the Japanese bio-weapons program that U.S. intelligence had heard.  These rumors were based on a sizeable body of letters MacArthur's intelligence office in Tokyo had received from numerous sources.

Sanders was desperate for information concerning Japanese bio-weapons.  But as he continued to delve into the subject, he found that the people he interviewed would tell him nothing unless they were promised some kind of protection from prosecution for their activities.  Making matters even more complicated for Sanders was the fact that the man assigned to be his interpreter was none other than Lieutenant Colonel Ryoichi Naito, a former member of Unit 731.  Sanders appears to have been unaware of this at the time.  Being neither a Japanese speaker nor a scientist, Sanders also did not know that Colonel Ryoichi actively participated in weaving a web of half-truths and outright lies concerning Unit 731.  Colonel Ryoichi eventually persuaded Sanders that witnesses would talk only if they were promised immunity from prosecution.  The result, according to the scholar Tien-wei Wu, was that 

"Sanders approached General Douglas MacArthur saying: 'My recommendation is that we promise Naito that no one involved in BW will be prosecuted as war criminal.'  The recommendation was readily accepted by MacArthur.  By September, Sanders discovered that Unit 731 was involved in human experiments and he took the issue to MacArthur whose response was, 'We need more evidence.  We can't simply act on that. Keep going.  Ask more questions.  And keep quiet about it'."[1]

Murray Sanders was soon followed by another investigative team headed by Lieutenant Colonel Arvo Thompson.  Thompson worked closely with the intelligence branch of the SCAP (Supreme Command Allied Powers) in Japan.  Throughout late 1945 and into 1946 Thompson followed leads, questioned witnesses, and interrogated members of the Unit 731 staff.  Thompson was then followed by Norbert Fell, a microbiologist who also came from Ft. Detrick.  The work of Thompson, and especially Fell, led directly to Ishii Shiro and several of his most important subordinates, including General Wakamatsu Yujiro, Major General Kitano Masaji, and Lieutenant Colonel Ryoichi Naito.  These investigations concluded decisively that not only had the Japanese conducted substantial and extensive biological and chemical weapons tests in Manchuria, they had done so on civilians and Allied POWs, including Americans.  In addition, Fell concluded that the level of Japanese research was so advanced it had reached the point at which scientific conclusions could be drawn.


Simultaneous to the investigations of Unit 731, an increasingly large number of Japanese war criminals were being tried in Tokyo for crimes against humanity.  Initially, according to Sheldon Harris in his well-researched book Factories of Death, Ishii and his colleagues feared that they too would be tried for war crimes.  However, they were soon made aware that it was more important to the Americans to collect information on bio-weapons than it was to prosecute the men of Unit 731.  It appears that from the very beginning of their investigative efforts, the Americans were more interested in learning that they could from Ishii than in bringing him and the others to justice.  At one point Sanders had even said men like Ishii "were in no danger of being charged with war crimes should they provide him with details of their BW investigations".[2]  Despite his promise, Sanders' investigation had been severely hampered by continued Japanese stonewalling and deception.  Unit 731 veterans were simply too afraid of prosecution for their wartime activities.  It would only be during Norbert Fell's subsequent investigation that the information would truly begin to flow.  In one of his reports, Fell mentioned that 'The Japanese were assured that war crimes were not involved".  Once word of this had passed through the grapevine, former members of Unit 731 began contacting Fell to offer him the information they had.[3]

In the end, Fell accumulated a significant amount of detailed evidence about the Japanese weapons program.  He also accumulated enough evidence to classify the major players in Unit 731, Ishii, Wakamatsu, Kitano, and several others, as major war criminals.  However, the price for getting the information out of Ishii and the others was promising these men immunity from prosecution.

The problem is that Fell was not of sufficient rank or influence to have granted Ishii and the others immunity.  For this Fell needed to consult with Washington.  Sheldon Harris describes a meeting held in Washington, D.C. on June 23, 1947 during which "representatives from the War, State, and Justice Departments ... 'informally agreed' to accept 'the recommendations of the C. in C., FEC [General MacArthur], and the Chief, Chemical Corps [General Alden Waitt], i.e. that all information obtained in this investigation would be held in intelligence channels and not used for 'War Crimes' programs".[4]  Approval for this informal agreement was then kicked upstairs to the Joint Chiefs of Staff, which appears to have authorized the immunity promise.  The problem here is that the Joint Chiefs do not approve political policies.  Therefore, final authorization for immunity must have come from President Truman.[5]  From this point on not a single former Japanese officer, doctor, or scientist who had been involved in biological or chemical weapons research in Manchuria would be prosecuted.  Unit 731 was never even mentioned in the records of the Tokyo war crimes trials.  It was as if the operations of Unit 731 had never happened.

Even before the decision in Washington to hide the facts of Japanese biological weapons research and atrocities, MacArthur's command in Japan had erected a wall of silence surrounding the entire issue.  According to information compiled by Tien-wei Wu,

"Taking a hint from MacArthur, Chief Prosecutor of the Tokyo Trial Joseph B. Keenan (a Democrat politician from Ohio) suppressed the Soviet accusation against Japanese biological warfare criminals.  Maj. Gen. Charles Willoughby, MacArthur's intelligence chief, was in charge of the whole affair of Unit 731, shielding its former members from any outside contact in order to avoid any research data on biological warfare fallen into the Soviet hands.  Despite the fact that Lt. Col. Thomas H. Morrow (a lawyer from Ohio) of International Prosecution Section of the Tokyo Trial and David N. Sutton, head of its Document Division, made a trip to China to collect evidence on Japanese waging biological warfare in China, during the afternoon of August 29, 1946 no sooner was the Unit 731 case raised than it was dropped.  MacArthur was empowered 'to approve, reduce or otherwise alter any sentence imposed by "the International Military 'Tribunal the Far East'."[6]

In 1949, the Soviets officially requested access to records and Japanese personnel as part of their own investigation into Japanese biological warfare crimes.  These requests were either summarily ignored or refused by American authorities.  Given the increasingly hostile environment of the developing Cold War there would be no information sharing with the USSR.

In addition to opposing the Soviets, the U.S. military had another very good reason for keeping biological warfare information secret, it was trying to glean the benefits of Japanese data for it's own biological and chemical warfare programs.  The information and the expertise provided by Ishii and his colleagues was crucial to U.S. weapons research.

Therefore, at the same time that American prosecutors and judges were sitting on tribunals trying Nazi war criminals for their crimes, the U.S. government was becoming ever more deeply involved in covering up some of the worst atrocities committed during the Second World War. 

For example, as the State-War-Navy Department's Sub-Committee for the Far East concluded in a report dated August 1, 1947:

"Experiments on human beings similar to those conducted by the Ishii group have been condemned as war crimes by the International Military Tribunal for the trial of major Nazi war criminals in its decision handed down at Nuremberg on September 30, 1946.  This Government is at present prosecuting leading German Scientists and medical doctors at Nuremberg for offenses which included experiments on human beings which resulted in the suffering and death of most of those experimented on. ... [Nevertheless] The value to the U.S. of Japanese BW data is of such importance to national security as to far outweigh the value accruing from war crimes' prosecution."[7]


Thus a cynical bargain was struck.  Atrocities committed by Unit 731 personnel were forgotten in exchange for information about biological and chemical weapons that the U.S. could use for its own programs.  It is perhaps worth noting here that, to its credit, the State Department argued strongly against covering-up the crimes of Unit 731, claiming that "such a course would be a violation of international laws and detrimental to human morality and once revealed, it would be a source of serious embarrassment to the United States".[8]

In the decades afterward, the former members of Unit 731 went on to assume prominent positions and start lucrative careers in Japanese society.  Naito Ryoichi, for one, became the head of the Green Cross pharmaceutical company.  Public knowledge about Unit 731 only came to light in 1989 after an article was published in the now defunct Japanese magazine Days Japan.  Compensation cases are still occasionally initiated against the government of Japan by victims of the Unit 731 experiments.  However, these cases always end up being thrown out by the courts (See "The Asian Auschwitz of Unit 731").  To this day the victims of biological and chemical experiments in Manchuria have received neither compensation nor an apology for Japanese wrong-doing.


To this point in time (summer 2006), the United States government continues to sit on a large number of Japanese records that were seized by the U.S. Army during the post-war occupation of Japan.  These records have been classified since 1945 and are held in the National Archives and Records Administration facility in College Park, MD.  Scholars anticipate that a certain percentage of these records contain detailed information about the activities of Unit 731.  However, no one knows this for certain.

In 2000, the U.S. Congress passed the Japanese Imperial Government Disclosure Act.  This act allegedly authorized the disclosure to the public of all records from the Empire of Japan that are held at NARA.  The cataloging and release of these records falls under the responsibility of the The Nazi War Crimes and Japanese Imperial Government Interagency Working Group (IWG).  The IWG has been empowered to

  1. Locate, identify, inventory, recommend for declassification, and make available to the public at the National Archives and Records Administration (NARA), all classified Japanese Imperial Government records of the United States;
  2. Coordinate with agencies and take such actions as necessary to expedite the release of such records to the public; and
  3. Submit a report to Congress, including the Committee on Government Reform and the Permanent Select Committee on Intelligence of the House of Representatives, and the Committee on the Judiciary and the Select Committee on Intelligence of the Senate, describing all such records, the disposition of such records, and the activities of the Interagency Group and agencies under this section.

Despite this mandate no records pertaining to Unit 731 or the Japanese biological and chemical weapons program have appeared.  It is also not likely that they will appear given the fact that Section 803, Sub-Section (b), Line 3 stipulates that records which "reveal information that would assist in the development or use of weapons of mass destruction" are exempt from release.  Given that biological and chemical weapons are categorized as weapons of mass destruction it remains to be seen if any of the classified records at NARA on Unit 731 ever become available to the public.



This title may be cited as the `Japanese Imperial Government Disclosure Act of 2000'.


(a) DEFINITIONS- In this section:
(1) AGENCY- The term `agency' has the meaning given such term under section 551 of title 5, United States Code.
(2) INTERAGENCY GROUP- The term `Interagency Group' means the Nazi War Crimes and Japanese Imperial Government Records Interagency Working Group established under subsection (b).
(3) JAPANESE IMPERIAL GOVERNMENT RECORDS- The term `Japanese Imperial Government records' means classified records or portions of records that pertain to any person with respect to whom the United States Government, in its sole discretion, has grounds to believe ordered, incited, assisted, or otherwise participated in the experimentation on, and persecution of, any person because of race, religion, national origin, or political opinion, during the period beginning September 18, 1931, and ending on December 31, 1948, under the direction of, or in association with--
(A) the Japanese Imperial Government;
(B) any government in any area occupied by the military forces of the Japanese Imperial Government;
(C) any government established with the assistance or cooperation of the Japanese Imperial Government; or
(D) any government which was an ally of the Japanese Imperial Government.
(4) RECORD- The term `record' means a Japanese Imperial Government record.
(1) IN GENERAL- Not later than 60 days after the date of the enactment of this Act, the President shall designate the Working Group established under the Nazi War Crimes Disclosure Act (Public Law 105-246; 5 U.S.C. 552 note) to also carry out the purposes of this title with respect to Japanese Imperial Government records, and that Working Group shall remain in existence for 3 years after the date on which this title takes effect. Such Working Group is redesignated as the `Nazi War Crimes and Japanese Imperial Government Records Interagency Working Group'.
(2) MEMBERSHIP- Section 2(b)(2) of such Act is amended by striking `3 other persons' and inserting `4 other persons who shall be members of the public, of whom 3 shall be persons appointed under the provisions of this Act in effect on October 8, 1998.'.
(c) FUNCTIONS- Not later than 1 year after the date of the enactment of this Act, the Interagency Group shall, to the greatest extent possible consistent with section 803--
(1) locate, identify, inventory, recommend for declassification, and make available to the public at the National Archives and Records Administration, all classified Japanese Imperial Government records of the United States;
(2) coordinate with agencies and take such actions as necessary to expedite the release of such records to the public; and
(3) submit a report to Congress, including the Committee on Government Reform and the Permanent Select Committee on Intelligence of the House of Representatives, and the Committee on the Judiciary and the Select Committee on Intelligence of the Senate, describing all such records, the disposition of such records, and the activities of the Interagency Group and agencies under this section.
(d) FUNDING- There is authorized to be appropriated such sums as may be necessary to carry out the provisions of this title.


(a) RELEASE OF RECORDS- Subject to subsections (b), (c), and (d), the Japanese Imperial Government Records Interagency Working Group shall release in their entirety Japanese Imperial Government records.
(b) EXEMPTIONS- An agency head may exempt from release under subsection (a) specific information, that would--
(1) constitute an unwarranted invasion of personal privacy;
(2) reveal the identity of a confidential human source, or reveal information about an intelligence source or method when the unauthorized disclosure of that source or method would damage the national security interests of the United States;
(3) reveal information that would assist in the development or use of weapons of mass destruction;
(4) reveal information that would impair United States cryptologic systems or activities;
(5) reveal information that would impair the application of state-of-the-art technology within a United States weapon system;
(6) reveal United States military war plans that remain in effect;
(7) reveal information that would impair relations between the United States and a foreign government, or undermine ongoing diplomatic activities of the United States;
(8) reveal information that would impair the current ability of United States Government officials to protect the President, Vice President, and other officials for whom protection services are authorized in the interest of national security;
(9) reveal information that would impair current national security emergency preparedness plans; or
(10) violate a treaty or other international agreement.
(1) IN GENERAL- In applying the exemptions provided in paragraphs (2) through (10) of subsection (b), there shall be a presumption that the public interest will be served by disclosure and release of the records of the Japanese Imperial Government. The exemption may be asserted only when the head of the agency that maintains the records determines that disclosure and release would be harmful to a specific interest identified in the exemption. An agency head who makes such a determination shall promptly report it to the committees of Congress with appropriate jurisdiction, including the Committee on the Judiciary and the Select Committee on Intelligence of the Senate and the Committee on Government Reform and the Permanent Select Committee on Intelligence of the House of Representatives.
(2) APPLICATION OF TITLE 5- A determination by an agency head to apply an exemption provided in paragraphs (2) through (9) of subsection (b) shall be subject to the same standard of review that applies in the case of records withheld under section 552(b)(1) of title 5, United States Code.
(d) RECORDS RELATED TO INVESTIGATIONS OR PROSECUTIONS- This section shall not apply to records--
(1) related to or supporting any active or inactive investigation, inquiry, or prosecution by the Office of Special Investigations of the Department of Justice; or
(2) solely in the possession, custody, or control of the Office of Special Investigations.


Unit 731 and General Ishii Shiro

Brief History of the Japanese Biological Weapons Program

General Ishii Shiro: Commander of Bio-Weapons Program

Review of Studies of Japanese Biological Warfare in the United States

Unit 731

The Cover-Up of Unit 731

A Brief History of Unit 731

Japanese Experiments on Humans

"Japanese Medical Atrocities in World War II" by Sheldon Harris

"Scientific Atrocities: A Comparison of Japanese and Nazi Human Experimentation"

War Crimes Trials and Government Actions

The Tokyo War Crimes Trials: A Summary

The Truman Library: Tokyo War Crimes Trials

The Defendants at the Tokyo War Crimes Trials

The International Military Tribunal for The Far East

Charter of the International Military Tribunal for the Far East

The Failure of the Tokyo War Crimes Trials

The Khabarovsk War Crimes Trials
Unlike the American tribunal in Tokyo, in 1949, this Soviet tribunal tried captured Japanese officers involved in illegal biological and chemical weapons testing.

The Nazi War Crimes and Japanese Imperial Government Interagency Working Group (IWG)
This group of scholars and others is responsible for the investigation, organization, and de-classification of historical records dealing with Nazi Germany and Imperial Japan.

IWG Japanese Interim Report (March 2002)


Buy Factories of Death: Japanese Biological Warfare 1932 to 1945 and the American Cover-Up by Sheldon Harris

Buy A Plague Upon Humanity: The Secret Genocide of Axis Japan's Germ Warfare Operation by Daniel Barenblatt


1) Tien-wei Wu, "A Preliminary Review of Studies of Japanese Biological Warfare and Unit 731 in the United States"

2) Sheldon Harris, Factories of Death: Japanese Biological Warfare, 1932-1945, and the American Cover-Up (Routledge, 1995), p. 191.

3) Harris, Factories, p. 196.

4) Harris, Factories, p. 196.

5) Harris, Factories, p. 204.

6) Tien-wei Wu, "A Preliminary Review of Studies of Japanese Biological Warfare and Unit 731 in the United States"

7) Tien-wei Wu, "A Preliminary Review of Studies of Japanese Biological Warfare and Unit 731 in the United States"

8) Tien-wei Wu, "A Preliminary Review of Studies of Japanese Biological Warfare and Unit 731 in the United States"