Pardoning Devils: The American Cover Up of Imperial Japanese Unit 731

By: Ian Schneier

After General Douglas MacArthur accepted the official surrender of Japan on September 2nd, 1945, work began on the compilation of evidence of Japanese war crimes, eventuating in the establishment of the International Military Tribunal for the Far East (IMTFE).[1] The tribunal’s initial charter states, “As one of the terms of surrender… stern justice shall be meted out to all war criminals.”[2] Adding to Imperial Japan’s irreparably tarnished image were the seemingly unending accounts of Japanese atrocities committed across mainland Asia and the Pacific islands. Rape, torture, and astonishingly creative cruelty grew to characterize the Imperial Japanese military.[3] It could be reasonably expected that Allied forces would have upheld the charter of the IMTFE, prosecuting Japanese war criminals to the fullest extent available. Unfortunately, some of the worst Japanese crimes against humanity were deliberately omitted from human rights tribunals: the chemical and biological experimentation on Chinese and Allied POWs by Imperial Army Unit 731. Although responsible for some of the most grotesque atrocities committed in either theater of the Second World War, much of Unit 731 was granted immunity from war crimes prosecution by the United States government.[4] By granting immunity to the leaders of Unit 731, the United States set a precedent that America would overlook any violation of human rights, no matter how horrific or illegal, if it were politically or strategically expedient to do so.

Unit 731

Established by Emperor Hirohito in 1936, Unit 731’s exact mission varied over the course of its operations, but two main focuses remained constant. First, the Imperial Army of Japan wanted to research and develop the creation of biological or chemical agents which, if necessary, could be weaponized against Allied civilian populations.[5] Second, the Unit was tasked with researching the effects of extraordinary conditions on the human body with the aim of bettering the treatment of Japanese soldiers in combat.[6] In the pursuit of both aims, Unit 731 conducted experiments unique in both their extreme creativity and brutality. During the research of weaponized chemical and biological agents, ‘field tests’ were repeatedly conducted in mainland China on unsuspecting Chinese civilians; these field tests often entailed the bombing of Chinese villages with clay molds filled with thousands of plague infected fleas in order to observe the lethality and transmissibility of the plague.[7] Other field tests focused on the production of bacterial agents that would be used to poison enemy rivers or infect enemy crops, highlighting the Imperial Japanese Army’s goal of targeting Allied civilian populations.[8] The bulk of this research involved experimentation on live human test subjects.  Rather than calling them people, Unit 731’s scientists callously labeled these human subjects “logs” (marutas in Japanese).[9] Logs were subjected to whatever conditions the Imperial Japanese army saw appropriate to investigate, without anesthetic. Logs¸ who included infants, women, and children, were poisoned, starved, burned, boiled, electrified, dehydrated, gassed, and frozen to death.[10] To study the effects of frostbite and test various methods of treatment, logs would have limbs forcibly submerged in ice water until the limbs had frozen and swollen.[11] In order to observe the effects of various diseases on the human body, logs would be infected with lethal diseases and then dissected while still alive.[12] In order to determine the limits of human blood loss, logs underwent blood transfusions with horse blood.[13] Female logs were often raped in order to examine the effects of venereal diseases on developing fetuses who were then vivisected (cut open while alive) alongside their mother.[14] These examples of Unit 731’s human experimentation, macabre as they are, do not come close to encompassing all of the horrific experiments and research conducted by Unit 731; however, these terrible examples do illustrate the gravity of the United States’ decision to pardon the leadership of Unit 731. By pardoning the experimenters who vivisected innocent men, women, and children, the American government set the dangerous precedent that it would intentionally overlook any violation of human rights if it were provided reason enough to do so.

Political/Military Landscape

In 1945, the United States’ explicit strategic reason to pardon members of Unit 731 was the threat posed by the USSR. Unit 731’s experiments, horrific as they were, provided enormous amounts of useful medical knowledge and data to the United States Army regarding biological and chemical warfare.[15] After gathering the Unit’s data, General Douglas MacArthur decided that the information learned by members of Unit 731 had the potential to be of major strategic importance in a future war against the Soviet Union.[16] This meant that the secrecy of Unit 731’s data became a strategic priority and that all information gathered on the Unit would be strictly confidential, precluding Unit 731’s inclusion in the Tokyo War Crimes Trail.[17] The U.S. Army’s response to public inquiry regarding Japanese experimentation on human subjects was a mix of feigned ignorance, outright deception, and intentional suppression. When prodded by American journalists, U.S. Army leadership repeatedly claimed to have found no evidence of Japanese experimentation on human test subjects.[18]

Over time, this continued refusal to acknowledge the crimes of Unit 731 began to create issues between the United States and Allied nations in the Pacific, namely the USSR. Soviet troops had captured multiple research facilities used by Unit 731 in Manchuria and concluded that the Imperial Japanese Army had been performing biological experiments on Allied POWs.[19] After Soviet intelligence gathered the necessary evidence, they established a human rights tribunal in the eastern-Russian city of Khabarovsk. The trial at Khabarovsk, in keeping with the Stalinist traditions of the time, was less a trial and more a ten-day retelling and condemnation of the Japanese human experiments in Manchuria; however, the Khabarovsk trial deserves recognition as the only public forum at the time which discussed and released information regarding the atrocities committed by Unit 731.[20] Tellingly, the findings of the Khabarovsk trials, “Were publicly dismissed by U.S. authorities as communist propaganda.”[21] Furthermore, “The Soviet Prosecutor at the IMTFE attempted to initiate a new tribunal to try other Unit 731 personnel… but, MacArthur ensured that his initiatives were thwarted.”[22] Although American strategic preparations for a war with the Soviet Union were not unfounded, the decisions made by General Douglas MacArthur to cover up the atrocities of Unit 731 placed the United States Army in the morally reprehensible position of being less forthcoming than Joseph Stalin’s Soviet Union.

Altruistic as the Khabarovsk trial appears in comparison to the United States’ silence on Japanese experimentation, the Soviet Union was still a proponent of ideals and values which were devoid of freedom, justice, or the humane treatment of civilians. While hundreds of thousands were likely killed or harmed in Unit 731’s experiments, millions died in Stalin’s purges, labor camps, and famines.[23] This should not detract from the guilt and terror attributable to Unit 731, but it should provide some context of the situation U.S. Army leaders found themselves facing after having conquered Imperial Japan. Context, however, does not equal condonement.

Decisions and Impact

A complex situation and the necessity for difficult decisions does not morally exonerate U.S. Army leadership and General MacArthur from the simple fact that they covered up some of the worst atrocities of the 20th century. Making the U.S. Army’s cover up more egregious is the fact that numerous sources indicate American POWs were repeatedly used in these horrific experiments, a contention General MacArthur repeatedly denied and suppressed.[24] With the choice to not only grant immunity but to publicly defend the scientists of Unit 731, General MacArthur made the decision to prioritize strategic and political goals above justice for the unnamed American servicemen who died in Japanese labs. This decision had obvious implications for American legitimacy overseas, as covering up the nightmarish actions of Unit 731 directly detracted from any position of American ethical superiority. But this decision also had more nuanced implications regarding the U.S. Army’s relationship with the American people. What precedent was set, when the United States’ most trusted institutions, its military, became complicit in the cover up of some of the worst atrocities committed in human history?

By prioritizing political precautions against Japanese communists, the American military chose political expediency over Imperial Japanese accountability. By prioritizing strategic precautions against the Soviet Union, the U.S. Army chose data and results over justice for Allied POWs murdered by Unit 731. The decision made by General Douglas MacArthur to shield Unit 731 from prosecution set a precedent that the American government and military would overlook violations of international law, human rights abuse, or outright evil if it were advantageous to do so. By acknowledging the fact that this precedent was set in the past, the U.S. Army can begin to repair the wrongs of its predecessors and ensure that similar moral failings are avoided in the future.

Implications for Leaders Today

A Google search of “US military misconduct” will return thousands of recent examples of unethical and immoral decisions made by US military leaders.  In ethics there is a concept called ethical fading.  Ethical fading is where the ethical aspects of a decision fade away and are replaced by some other criteria, such as winning, self-interest, or profitability to name a few.  A 2015 US Army War College study discussed how lying is common in the military. 

“…officers tended to dodge the issue [of unethical behavior] with statements such as, “You gotta make priorities, we met the intent, or we got creative.” Eventually words and phrases such as “hand waving, fudging, massaging, or checking the box” would surface to sugarcoat the hard reality that, in order to satisfy compliance with the surfeit of directed requirements from above, officers resort to evasion and deception. In other words, in the routine performance of their duties as leaders and commanders, U.S. Army officers lie.”[25]

So, what does this all mean?  It means we as leaders are constantly facing ethical dilemmas.  Some may be on a scale of General MacArthur, but most are much smaller.  Yet, both present difficult dilemmas with potentially lasting implications for one’s career, the profession, and potentially the nation.  Should leaders win at all costs?  Where is the line between acceptable and unacceptable?  What are the ethics of hiding or covering up an egregious act?  Is it ethical to “massage the truth” or “check the box”?  What does it say about our leadership if we deprioritize or put ethics to the side?  These are questions every leader must answer because leaders set the ethical climate for the organization. 


Ian Schneier is a cadet at the United States Military Academy at West Point. He is from Nashville, TN and is currently studying international history.


Photo Source: The U.S. National Archives

[1] “Japan Surrenders,” National Archives- Exhibits- Feature Documents. (accessed Nov 23, 2020).

[2] International Military Tribunal for the Far East. Tokyo, Japan. January 19, 1946, International Military Tribunal for the Far East 3.

[3] Lord Russell, The Knights of Bushido: A Short History of Japanese War Crimes (London, UK: Cassell & Company LTD, 1958), 53-69.

[4] Brody, Leonard, Nie, and Weindling. “U.S. Responses to Japanese Wartime Inhuman Experimentation after World War II.” Cambridge Quarterly of Healthcare Ethics 23, no. 2. (March 2014): pp 220.

[5] Nicholas D. Kristof, “Unmasking Horror – A Special Report.; Japan Confronting Gruesome War Atrocity,” The New York Times, March 17, 1995.

[6] “Unit 731,” Atomic Heritage Foundation, May 4, 2018. (accessed Nov 23, 2020).

[7] Richard Stockton, “Inside Unit 731, World War II Japan’s Sickening Human Experiments Program,” All That’s Interesting. November 2, 2017.

[8] Wallace, Unit 731: Japan’s Secret Biological Warfare in World War II, 29-30.

[9] Sheldon Harris, Factories of Death (New York, NY: Routledge, 1994), 62-63.

[10] Wallace, Unit 731: Japan’s Secret Biological Warfare in World War II, 31-50.

[11] Richard Stockton, “Inside Unit 731, World War II Japan’s Sickening Human Experiments Program.”

[12]Justin McCurry, “Unit 731: Japan discloses details of notorious chemical warfare division.” The Guardian, April 17, 2018.

[13] Wallace, Unit 731: Japan’s Secret Biological Warfare in World War II, 41.

[14] Ibid.

[15] Katrien Devolder. “U.S. Complicity and Japan’s Wartime Medical Atrocities: Time for a Response.” American Journal of Bioethics 15, no. 6. (June 2015): pp 41-42.

[16] Brody, Leonard, Nie, and Weindling. “U.S. Responses to Japanese Wartime Inhuman Experimentation after World War II,” 224.

[17] Katrien Devolder. “U.S. Complicity and Japan’s Wartime Medical Atrocities: Time for a Response.” pp 42.

[18] “Japan Said to Test Germ War on G.I.’s.”, “No Knowledge, MacArthur Says”, “U.S. Aid Found No Evidence,” 16.

[19] William Gill, War Crimes Investigations in Japan 1945-1948: A Personal Remembrance (Auburn, Alabama. 1995), 51-53.

[20]Russell Working, “The Trial of Unit 731.” The Japan Times. June 5, 2001.

[21] Katrien Devolder, “U.S. Complicity and Japan’s Wartime Medical Atrocities: Time for a Response,” 42.

[22] Gill, War Crimes Investigations in Japan 1945-1948: A Personal Remembrance, 52.

[23]Cynthia Haven, “Stalin Killed Millions. A Stanford Historian answers the Question, was it Genocide?” Stanford News. September 23, 2010.

[24] Gill, War Crimes Investigations in Japan 1945-1948: A Personal Remembrance, 52.

[25] Leonard Wong Dr. and Stephen J. Gerras Dr., Lying to Ourselves: Dishonesty in the Army Profession ( US Army War College Press, 2015),