1942—1944: Americans began to capture numerous Japanese military orders, diaries, and field notebooks that contained evidence of Japanese atrocities. The task was carried out by the US Army’s Allied Translator & Interpreter Section (ATIS), the largest translation and interrogation operation in the Pacific which was established by Gen. MacArthur in 1942. ATIS began translating documents and making them available to U.S. military and intelligence organizations.

The ATIS translations and reports were sealed, designated Top Secret until the enactment of the Japanese Imperial Government Disclosure Act and the establishment of the Interagency Working Group (IWG, 2000) under the aegis of the National Archives and Records Administration (NARA). The IWG was tasked with locating, identifying and declassifying World War II documents and making them publicly accessible under the Freedom of Information Act; and submitting a report to Congress.

In February 1943, MacArthur asked Brig. Gen. Charles A. Willoughby, his G-2 (Intelligence) chief, to provide him with materials relevant to Japanese war crimes. Willoughby turned to Col. Sidney Mashbir, Chief of ATIS, who produced several ATIS reports and preliminary interrogative material related to cannibalism, torture, and other war crimes.

ATIS continued to receive evidence of Japanese atrocities such as beheadings, vivisection, and cannibalism during 1943 and 1944.  In late 1944 and early 1945, ATIS published Research Reports on Japanese Tactics: Report #84, “Japanese and Bacterial warfare,” Report #117, “Infringement of the Laws of War and Ethics by the Japanese Medical Corps.” (IWG. An Interim Report to Congress, 2002)

In August 1945, General Douglas MacArthur became Supreme Commander of the Allied Powers stationed in Tokyo. Within weeks Lt. Colonel Murray Sanders arrived from Ft. Detrick to investigate rumors about Japanese biological weapons program that U.S. intelligence had learned about. The rumors were based on numerous letters received by MacArthur’s intelligence office.

On Sept. 3, 1945, the day after Japan’s surrender, Col. Mashbir confronted Okzaki Katsuo, Japan’s Ministry of Foreign Affairs with evidence of

“grisly and compelling evidence of extensive Japanese war crimes against civilians and POWs. Mashbir produced Japanese military orders to burn to death Filipino men, women and children, and showed Okazaki photographs of the horrors of Manila.” (IWG. Researching Japanese War Crimes, Ch. 6, 2006)

The U.S. government shielded Japanese mass murders & helped cover-up a vast network of murder
Col. Sanders’ investigation was hampered by Japanese and U.S. intelligence stonewalling. He was followed by another investigative team headed by Lt. Colonel Arvo Thompson who throughout late 1945 and 1946, questioned witnesses and interrogated members of Unit 731. He was followed in April 1947, by Norbert Fell, a microbiologist from Ft. Detrick whose investigation led directly to Shiro Ishii and several of his most important subordinates.

“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.” (Japanese Biological Warfare Atrocities and the U.S. Cover-Up, World Future Fund)

At the same time of these investigations of Unit 731, a large number of Japanese war criminals were being tried in Tokyo for crimes against humanity. Initially, according to Sheldon Harris, Ishii and his colleagues feared that they too would be tried for war crimes. But they soon realized that the Americans were more interested in collecting information on bio-weapons than on prosecuting the men of Unit 731. (Harris. Factories of Death: Japanese Biological Warfare, 1932-45, and the American Cover-Up, 1994) Norbert Fell’s subsequent investigation was the more fruitful after he let it be known 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.”

“On June 23, 1947, a meeting with representatives from representatives from the War, State, and Justice Departments … ‘informally agreed’ to accept ‘the recommendations of [General MacArthur], and the Chief, Chemical Corps, i.e. that all information obtained in this investigation would be held in intelligence channels and not used for ‘War Crimes’ programs.” (Harris, p. 196)

“Approval for this informal agreement was then kicked upstairs to the Joint Chiefs of Staff, which appears to have authorized the immunity promise. However, the Joint Chiefs do not approve political policies.  Therefore, final authorization for immunity must have come from President Truman. (p. 204)

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.

News reports about American victims of Ishii’s human experiments surfaced as early as Jan. 6, 1946 in Pacific Stars and Stripes, an official organ of the U.S. Army and in The New York Times, a week later. A U.S. government document dated August 1947 stated:

“It should be kept in mind that there is a remote-possibility that independent investigation conducted by the Soviets in the Mukden area may have disclosed evidence that American prisoners of war were used for experimental purposes of a BW nature and that they lost their lives as a result of these experiments.” (Tien-wei Wu. A Preliminary Review of Studies of Japanese Biological Warfare and Unit 731 in the United States)

Justice B.V.A Roling, the only surviving judge from the International Military Tribunal for the Far East in Tokyo (Asia’s Nuremberg), felt betrayed when he learned about the concealed evidence of biological warfare experimentation had been concealed from the court. He complained that no word about biological warfare had been offered in evidence:

“It is a bitter experience for me to be informed now that centrally ordered Japanese war criminality of the most disgusting kind was kept secret from the court by the U.S. government. This Japanese war criminality consisted, in part, of using human beings, prisoners of war, Chinese as well as American, as “guinea pigs” in an endeavor to test the impact of specific biological warfare weapons.” (Congressional Record. Nov. 10, 1999; quoted by Christopher Reed. The U.S. and the Japanese Mengele: Payoffs and Amnesty for Unit 731 Scientists, The Asia-Pacific Journal: Japan Focus, 2006)

The exact number of casualties attributable to Ishii’s abominable experiments is unknown. Tien-wei Wu disputes the number cited by Sheldon Harris who estimated 238 casualties and 1,617 survivors. Wu cites British, American and Australian former prisoners of war (some of who kept diaries); they estimated that out of 1,485 Allied white prisoners of war taken to Mukden, 1, 174 were Americans. In their first winter (1942-43) at Mukden, 430 perished; most of them, Americans.

Secret cables from U.S. Headquarters in Tokyo show Ishii negotiated “documentary immunity”
A series of Top Secret cables from U.S. Headquarters in Tokyo to the State War Navy Coordinating Committee in Washington show that Shiro Ishii was negotiating “documentary immunity” — he did not trust MacArthur’s oral promise. (The cables are cited by Robert Gromer, John Powell, and Burt Roling in their ground breaking article, “Japan’s Biological Weapons 1930-1945: A Hidden Chapter in History” Bulletin of Atomic Scientists (1981) (Reproduced in the Congressional Record, 1991)

May 6, 1947 cable described some of the information being secured:
“Statements obtained from Japanese here confirm statements of USSR prisoners. . . Experiments on humans were . . . described by three Japanese and confirmed tacitly by Ishii; field trials against Chinese took place . . . scope of program indicated by report . . . that 400 kilograms [880 lbs.] of dried anthrax organisms destroyed in August 1945. . . . Reluctant statements by Ishii indicate he had superiors (possibly general staff) who . . . authorized the program.”

“Ishii states that if guaranteed immunity from “war crimes” in documentary form for himself, superiors and subordinates, he can describe program in detail. Ishii claims to have extensive theoretical high-level knowledge including strategic and tactical use of BW on defense and offense, backed by some research on best agents to employ by geographical areas of Far East, and the use of BW in cold climates.”

Another Top Secret “memorandum for the record” (also dated May 6), gave more details: “USSR interest in Japanese BW personnel arises from interrogations of two captured Japanese formerly associated with BW. Copies of these interrogations were given to U.S. Preliminary investigation[s] confirm authenticity of USSR interrogations and indicate Japanese activity in: a. Human experiments; b. Field trials against Chinese; c. Large scale program; d. Research on BW by crop destruction; e. Possible that Japanese General Staff knew and authorized program; f. Thought and research devoted to strategic and tactical use of BW.

A Top Secret cable from Colonel Alva C. Carpenter, General Douglas MacArthur’s chief of legal staff and Cecil F. Hubbert, a member of the State, War, Navy Coordinating Committee, had recommended covering up the story of Japanese biological warfare experiments on American POWS. These military officials warned that the story might leak out if the Russian prosecutor brought the subject up during the Tokyo war crimes trials. Hubbert added that the Soviets might have found out that American prisoners of war were used for experimental purposes of a [biological warfare] nature and that they lost their lives as a result of these experiments.”  (Bulletin of the Atomic Scientists, 1981; Congressional Record, 1999)

According to Daniel Barenblatt, in 1947, MacArthur stated in a radio message to officials in the military and State Department: “Information about vivisection useful.”  MacArthur granted immunity from prosecution to all members of Unit 731 in exchange for their research data obtained from inhumane, barbarous medical and biological warfare experiments. (A Plague Upon Humanity: The Secret Genocide of Axis Japan’s Germ Warfare Operation (2004)

Professor Keiichi Tsuneishi, of Kanagawa University, is Japan’s leading specialist on biological warfare and Unit 731. He cites a report  by Edwin Hill and Joseph Victor dated December 12, 1947, addressed to US occupation authorities concerning human experimentation by Unit 731 and related facilities. It states:

“Evidence gathered in this investigation has greatly supplemented and amplified previous aspects of this field. It represents data which have been obtained by Japanese scientists at the expenditure of many millions of dollars and years of work. Information had accrued with respect to human susceptibility to those diseases as indicated by specific infectious doses of bacteria. Such information could not be obtained in our own laboratories because of scruples attached to human experimentation.”
(Keiichi Tsuneishi. Unit 731 and the Japanese Imperial Army’s Biological Warfare Program, The Asia-Pacific Journal: Japan Focus; Encyclopedia of world war crimes; Bungei Shunju, 2002) (Read also, Christopher Hudson. Doctors of Depravity, Daily Mail, 2007)

In 1999, Professor Sheldon Harris told a Tokyo audience that, the U.S. government Occupation Authorities were aware of the crimes against humanity committed by the human experimental Units.

“American scientists were eager to acquire the data the war criminals had developed on humans…  These scientists were anxious to deny the information to the United States’ erstwhile ally, The Soviet Union.  To achieve both goals, the scientists, with the collusion of Occupation authorities and members of the highest echelons in the US Government, negotiated with their former enemies for this information… eventually a Faustian bargain was struck between Japanese and American scientists.  The Japanese shared some of their secrets with the Americans.  The Americans in return granted the Japanese immunity from prosecution for war crimes.” (Harris. Japanese Medical Atrocities in WWII: Unit 731 Was Not An Isolated Aberration)

Tien-Wei Wu, a Chinese historian who received his doctorate from the University of Maryland and taught history at the University of Southern Illinois, noted that the State Department argued strongly against covering-up the crimes of Unit 731, stating 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.” However that view did not prevail.

Prof. Wu quotes the conclusion of a State-War-Navy Department report dated August 1, 1947 in which the U.S. prosecution of Nazi medical doctors at Nuremberg is acknowledged as is the similarity  of their crimes and those committed by the Japanese:

“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.” (Tien-wei Wu. A Preliminary Review of Studies of Japanese Biological Warfare and Unit 731 in the United States)

In March 1948, the Joint Chiefs of Staff cabled U.S. approval to MacArthur The U.S. government thus shielded Japanese mass murders and helped cover-up a vast network of sadistic medical murder. Evidence of the worst grizzly human experiments imaginable were concealed; and the mass murderers who committed crimes against humanity were given immunity.

There is no dispute about the lack of interest shown by high ranking U.S. government officials; nor about their lack of concern about the victims of diabolical medical war crimes, including U.S. servicemen who had been violated in heinous biological experiments. U.S. officials were focused on concealing the evidence and shielding the criminals responsible.

In 1958, Sugamo Prison in Tokyo was shut down after being emptied following the release of convicted Japanese war criminals — as per the order of General Douglas MacArthur. (Revisiting Japanese-American Internment, Interview with Linda Holmes, Asia Times, Oct. 13, 2011) The same year, the U.S. began returning some of the captured documents to Japan. (IWG. Researching Japanese War Crimes Records, 2006)

The U.S. was thus complicit in Japan’s cover-up of its worst crimes and atrocities; enabling Japan to dismiss the charges for decades. “What the US did in making the deal with top doctors is unconscionable.” (Japan’s Biowarfare Exposed, Taipei Times, March 2004)