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Exploring the Darker Side of Everything

Unit 731 – Imperial Japan’s Dark Biological and Chemical Testing Unit

World War II saw extensive cruelty in every shape and form. The Holocaust may stand as one of the most disturbing events in modern history, but the conflict also involved numerous other examples of when humanity stepped, not only well over the line, but into an area that can only be described as heinous – and our story today is one such example.   

With a name like the ‘Epidemic Prevention and Water Purification Department,’ you might be forgiven in thinking that Japan’s Unit 731, to use its informal name, was an admirable group fighting the good fight – but you could not be more wrong. 

To put it bluntly, the actions of this covert biological and chemical warfare research and development unit, which regularly involved lethal human experimentation on males and females, ranging in age from newborns to the elderly, were some of the darkest in a war filled with darkness.  

Imperial Japan on the Move

When we think of World War II we often simply focus our attention on the European theatre of conflict. If you ask your friend Google when the Second World War began, you will invariably be shown the date 1st September 1939, the date German tanks rumbled into Poland sparking declarations of war by both Britain and France. If you’re a European I suppose this makes perfect sense, however, by this point, a war had been raging thousands of miles away for some time. 

Yet even here, dates surrounding the beginning of the Asian side of the global conflict can be a little conflicting. The Japanese invaded Chinese Manchuria on 18th September 1931 but this was a much smaller operation than what was to come and saw the Japanese annexe the area before setting up a puppet government. 

Six years later, however, the Second Sino-Japanese War erupted after the Marco Polo Bridge Incident, in which a Japanese soldier, Private Shimura Kikujiro, temporarily disappeared, giving the Japanese army the perfect excuse to cross the border to investigate. Private Kikujiro soon reappeared, perhaps it was the worst timed toilet break in history, or maybe the Japanese fabricated the entire thing to find an excuse to start the war. Either way, full military conflict was now underway, a full two years before Hitler border crossing escapades in Poland. 

Japanese Occupation 

The Second Sino-Japanese War and the Japanese occupation of mainland China saw brutality on a scale that rivalled the Nazis and perhaps sometimes even beat Hier Hitler into second place. The Battle of Shanghai, which began on 13th August 1937, was the first major conflict between the two sides and set a pattern that would be repeated countless times in the early stages of the war – a spirited Chinese defence, but ultimately a crushing victory by the Japanese. 

But this war soon took a dark turn with the events that occurred in and around the city of Nanjing in December 1937 and January 1938. The number of Chinese civilians that remained in Nanjing when the Japanese military overran the city has been debated ever since, with confusion over how many had already fled and just how many were now sheltering within the Nanking Safety Zone, a series of small areas mainly encompassing foreign embassies that had rather ironically been set up by a member of the Nazi party. 

While the number of how many were killed during the Nanjing Massacre can be debated – the lowest estimate seems to be 30,000 and the highest 300,000 – the savagery of what occurred has long been clear. Mass murder and mass rape enveloped the city as Japanese soldiers indiscriminately tore through Nanjing. It provided one of the most horrifying episodes across the entire war, but by this point, the Japanese had begun something arguably even worse.         

Tōgō Unit

To begin the story of Unit 731, we need to backtrack a little to the Japanese invasion of Manchuria in 1931. At this point, there was an army unit with the name Army Epidemic Prevention Research Laboratory (AEPRL), which, as far as we know, began life as an innocent research and public health agency that dealt with protecting Japanese soldiers from chemical attacks on the battlefield.  

Japanese unit 731

But this changed in 1932 when Surgeon General Shirō Ishii, chief medical officer of the Imperial Japanese Army, was placed in charge of the AEPRL and formed a secretive sub-group under the name ‘Tōgō Unit’ – perhaps after General Hideki ‘Tōgō, the Japanese politician and General of the Imperial Japanese Army who would receive the bulk of the blame for starting the war with the United States.     

The Tōgō Unit was tasked with investigating and developing biological and chemical warfare from the Zhongma Fortress, a prison/experimentation camp in Beiyinhe, a village 100 km (62 miles) south of Harbin on the South Manchuria Railway. This was a tiny village of around 300 homes, which the Japanese burnt to the ground before expelling the local population, leaving only a large building that subsequently became the headquarters of the Tōgō Unit. 

Around the building, the Japanese constructed a prison camp that included a 3 metre high (9.8 ft) earthen wall topped with electrified barbed wire and a moat with a drawbridge. Inside, numerous buildings were erected, including housing units, barracks and dining halls, but also laboratories, warehouses and prison cells. This was all built through slave labour, mainly common criminals, captured bandits, anti-Japanese partisans, and political prisoners, all of whom were forced to wear blinders – like what you see on working horses – so they couldn’t get a full idea of what was being constructed. Those involved in the construction of most secretive buildings were executed as soon as work was completed. It had a capacity of 1,000, but it’s thought the prisoner population – who were referred to as ‘logs’ because the cover story of the site was that it was a wood mill – usually hovered around 500 or 600.  

Zhongma Fortress    

And here is where the horror begins. Once completed, the Japanese began rounding up prisoners, often criminals from the nearby area, mainly Chinese, but also a large number of Russian expatriates living in China. They were brought to the Zhongma Fortress and initially treated well with good food, including rice or wheat, meat and fish, and even a splash of alcohol to warm the body. But this was simply a disturbing attempt to bring the body into its natural healthy state before the experiments could begin. 

Now, I know that if you’ve come to a channel called Into the Shadows you’re probably expecting some pretty heavy material, but what occurred at the Zhongma Fortress and its later incarnations, was revulsion on an entirely different level. It was here that Japanese doctors and scientists conducted experiments on the prison population that looked at everything from the effects of the plague, cholera, starvation, water deprivation, frostbite, new weapons and much more. This was a sadistic house of horror, but the Zhongma Fortress was just the start, and we’ll be going into some of these experiments a little later in the video. 

Unit 731  

In the summer of 1934, around forty prisoners escaped from the Zhongma Fortress. Heavy rains had disabled the electrical fences, allowing escapees to scale the perimeter, despite being shackled at the feet. Ten were immediately killed by the guards on duty, while many were dragged back in to be subjected to the kind of torture that probably made their early experiences in Zhongma seem like a holiday camp. However, sixteen prisoners managed to elude the Japanese and disappeared into the neighbouring countryside. Japan’s dark secret was out. 

In response, Zhongma was closed in 1935, but this simply led to another, an even larger facility being opened in Pingfang, approximately 24 km (15 miles) south of Harbin. The following year the Tōgō Unit received a major shakeup and came under the direct jurisdiction of the Imperial Army while being divided into two, the “Ishii Unit” and “Wakamatsu Unit”. Initially, together they were known as the “Epidemic Prevention Department”, but from August 1940, it was referred to as the “Epidemic Prevention and Water Purification Department of the Kwantung Army or “Unit 731” 

At its largest, Unit 731 stationed in Pingfang was composed of 300 researchers, including doctors and bacteriologists, who would sometimes publish their findings in peer-reviewed scientific journals, failing to mention that many of the experiments were done on humans and not monkeys as was stated. But this was just one section of a much larger grim web that eventually included around 10,000 people across numerous units stationed in Manchuria, but also elsewhere, including Unit 1855 in Beijing, Unit Ei 1644 in Nanjing, Unit 8604 in Guangzhou and later, Unit 9420 in Singapore.  

The main location for Unit 731 was the site in Harbin, which measured six square kilometres (2.3 square miles) and included more than 150 buildings, many of which were factories used to produce chemicals or biological agents and the Harbin complex could produce 30 kilograms (66 pounds) of bubonic plague bacteria in just a few days. It was said that it included around 4,500 containers to be used to raise fleas, six enormous cauldrons to produce various chemicals, and around 1,800 large containers to produce biological agents. 

The typical life expectancy for prisoners in one of the Unit 731 complexes was around 2 months, though there were instances of some surviving for as long as 12 months, but these cases were often pregnant women who the Japanese wanted to give birth in order to investigate the effects of various diseases on the newborn child. And before we move on to talk about the experiments themselves, let’s just be very clear about the kind of facility we’re talking about. Nobody who came through the gates as a prisoner ever left alive.  

The Experiments 

The darkest actions carried out under the guise of Unit 731 came under the code-name Maruta – meaning logs – and varied wildly. 

It’s difficult to know where to start with this pit of absolute hell, so let’s dive straight in shall we. Many of the early experiments focused on how the body reacts to certain diseases and many prisoners were infected with syphilis, gonorrhoea and other venereal diseases. But that was just the start. While the Japanese were certainly interested in the visible external effects, it was often what was happening inside the body that they were really interested in. 

Vivisections, where the body is dissected for experimental purposes, was a common practice in Unit 731 on living humans, always without anaesthesia and with a rag stuffed into the mouth of the poor soul going under the knife to muffle the screams. This was done so that researchers could examine the effect of certain diseases on different bodily organs, but there has certainly been plenty of suggestion that at least some of the horror seen in Unit 731 was done so purely for sadistic pleasure. And it gets even weirder. Sometimes limbs would be amputated and reattached at different places on the body or internal organs removed then added back in but in different locations.  

Human Dissection Experiment Room
Human Dissection Experiment Room. By X20106301, is licensed under CC-BY-SA

Other prisoners were subjected to chemical weapons testing, including mustard gas, lewisite, cyanic acid gas, white phosphorus, adamsite and phosgene gas. Sometimes this was done in secure chambers, while there were widespread reports of large-scale experiments on the effects of mustard gas where prisoners were tied to posts outside. This was also done with plague, cholera, typhoid and anthrax, before it was taken to the next stage of testing which was usually done on a ‘live’ Chinese population, either through poisoned wells, aircraft drops, or fleas and other animals that had been infected with a disease. 

While the Japanese were eager to test the next generation of weapons that could kill thousands in one fell swoop, they didn’t neglect the tried and tested. Prisoners were used to test new grenades, flamethrowers and even bombs, which saw prisoners tied to posts at increasing distances from the explosion so that the damage radius could be measured. With new guns and bullets, wound patterns and penetration depths were carefully recorded and the same was done with bayonets, knives and swords. 

Experimentation regarding hypothermia was also a keen subject of interest in Unit 731 and typically involved limbs of prisoners being submerged in icy water until they were effectively frozen solid. Then researchers – or sadistic lunatics depending on how you want to call them – experimented to find the best way of heating the limb to return it to its normal state, sometimes using fire or boiling water and sometimes simply leaving the poor wretch overnight just to see what would happen. And yet – and I feel like I’ve said this already – that wasn’t the worst of it. The Japanese also did extensive experimentation to find out how quickly the human body would suffer from hypothermia and then die of exposure. They introduced different variables, such as when the prisoner had last eaten and what they had, what they were wearing and how much salt and protein they had in the body before the experiment. To perhaps sum up the horrifying actions of Unit 731 in one dreadful example, they found that a newborn baby will die in roughly three days if left unattended outside.  

I know that seems like a lot, but really we’ve just scratched the surface. Other experiments include giving prisoners the wrong blood transfusion or the blood of animals, injection of seawater, the human body’s tolerance for g-force using a rotating chamber, prolonged x-ray exposure, rape and forced pregnancy and probably a whole lot more that we’ll never completely know about. There were even horrific stories of bodies and body parts being pickled in formaldehyde, with the only labels visible being the nationality of whoever was inside.    

The End of the War & the Allied Cover Up            

With Japanese hopes fading towards the end of World War II, there appears to have been high-level discussion regarding the use of chemical or biological weapons against the allies and even on the U.S mainland using information and methods taken from the “research” done by Unit 731. It’s impossible to say how close this actually came, though an attack code-named Operation Cherry Blossom at Night which called for a biological attack on Southern California was certainly at some degree of planning when Japan surrendered in September 1945.

As the war ended, and Japan surveyed its destroyed country, Unit 731 was disbanded and its facilities in Manchuria and on the Japanese mainland were destroyed – along with much of the information regarding what had happened there. Prisoners remaining in the camps after Japan’s surrender were quickly executed and their bodies disposed of.   

But this was not something you could keep under wraps. When the Americans arrived in Japan, rumours of chemical and biological testing swirled, but little to no information was openly given to the Americans – for obvious reasons. It was only when the threat of Soviet involvement, and no doubt vicious vengeance came into play, were Japan’s dark secrets surrounding Unit 731 shared with the United States. A dossier detailing what occurred soon found its way to the desk of General Douglas MacArthur, the man tasked with rebuilding Japan, and some big decisions needed to be made over possible prosecutions. If there were ever war crimes committed, it was under the dark scope of Unit 731. 

However, the end of World War II saw an almost immediate pivot away from past enemies and towards new ones. For the Americans, the Japanese were no longer the enemy and they would do whatever they could to make life hard for those devious Soviets. General MacArthur authorised blanket immunity for those who worked in Unit 731, in exchange for sole ownership of the information and findings, which the United States deemed hugely valuable. In the Tokyo Trials, which saw twenty-eight Japanese military and political leaders tried for a variety of crimes, there was only a single solitary mention of chemical poisoning in occupied China and absolutely nothing about probably the most macabre experimentation unit across the entire war. 

The Soviets weren’t at all satisfied with this and instigated their own trials, known as the Khabarovsk War Crime Trials which began in December 1949. A total of 12 men were convicted of war crimes and sentenced to between 2 and 25 years in a Siberian labour camp. Now you might be thinking, well at least a few got what they deserved, but not really. Considering what had happened in Unit 731, these sentences were extraordinarily lenient and would you know it, most of those convicted soon found their way back to Japan, reportedly after handing over some of the secrets from Unit 731 to the Soviets. The United States refused to acknowledge the Khabarovsk Trials, labelling them as Soviet propaganda, but it’s crystal clear that both the U.S and Soviet Union let those responsible for the horror in Unit 731 off the hook, for their own gain.        

What followed was decades of near-silence in Japan with successive governments denying all knowledge of the activities of Unit 731. But by the turn of the millennium, with more and more people speaking about it, including those who had worked there, it was only a matter of time. In August 2008, the Tokyo district court ruled for the first time that Japan had engaged in biological warfare and directly named the work done by Unit 731. In 2018, after a request by Professor Katsuo Nishiyama of the Shiga University of Medical Science, the National Archives of Japan released the names of 3,607 members of Unit 731 – all of whom had lived freely since the end of the war and many of whom had since died. Apart from the 12 men who faced the ethically shaky Soviet trial in 1949, absolutely nobody was ever held accountable for their actions in Unit 731. In fact, many of them went on to quite illustrious careers in post-war Japan.    

A Dark Legacy 

In 2002, at an ‘International Symposium on the Crimes of Bacteriological Warfare’ in China, the number of people deemed to have been killed through Japanese chemical and biological warfare programs was estimated as 580,000, but that includes those killed through attacks outside the walls of the Unit 731 complexes as well as inside.  

It’s impossible to know the true number of those killed by Unit 731, but it’s thought that at least 3,000 men, women and children were experimented on, and killed, in the Pingfang site alone. This was not a place where anybody left alive – everybody who walked through the gates died one way or the other. The vast majority of these were Chinese, but large numbers of Russians and Koreans also perished in the Unit 731 facilities, along with lesser numbers of Mongols, Americans, British, and French. 

I said right at the start of the video that World War II delivered some sickening events and despicable cruelty but the actions of Unit 731 were on a different level. This wasn’t just blind torture and most of the experiments came with very particular purposes that in some ways actually managed to further scientific understanding, both for peaceful and military means, which is why both the U.S and the Soviet Union were so eager to gain access to the information. This may have been done under the shadowy guise of scientific experimentation, but it was some of the most sadistic, cruel science you are ever likely to see.  

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