Unit 731 and What Lies Behind the Distortions

For nearly eighty years, Unit 731 has stood as a grim reminder of Japan's wartime past, framed as a secret Japanese Imperial Army research group accused of human experimentation and the use of biological weapons in China. Yet according to Professor Issei Hironaka of Aichi Gakuin University, the history surrounding the unit has been shaped by ideology and emotion rather than objective inquiry.

In an exclusive interview with JAPAN Forward, Hironaka says, "History is about discovering what actually happened — evaluation comes after. If you start by calling something good or bad, the investigation ends before it begins."

Origins and Leadership of Unit 731

Unit 731 was established in 1936 under the Imperial Japanese Army as the Epidemic Prevention and Water Purification Department of the Kwantung Army. Officially tasked with preventing disease among troops, it expanded into research on biological and chemical warfare. The unit was headquartered in Pingfang, near Harbin, in what was then Japanese-occupied Manchuria, and operated several satellite facilities across northern China.

Its commander, Surgeon General Shiro Ishii, was a military physician who saw biological weapons as a strategic deterrent against the Soviet Union. Under his direction, the unit conducted experiments on pathogens such as plague, anthrax, and cholera, alongside field trials intended to test delivery methods.

By the end of the war, Unit 731 employed thousands of personnel, doctors, researchers, and soldiers, whose activities remain the subject of continuing debate among historians.

*Unit 731 complex in Habin (Wikimedia Commons)*

China's Selective Memory

Professor Hironaka devoted part of his research to the little-known issue of Chinese biological warfare. "I examined Japanese wartime survey materials that recorded Chinese forces using limited biological tactics — for example, tossing cholera bacteria into wells," he said.

While these incidents were small-scale, he believes they demonstrate that biological weapons were not the monopoly of any one side. According to Hironaka, this aspect is almost never mentioned in Chinese or Western scholarship. "If Chinese scholars admitted such evidence, their own narrative would lose consistency," he said. To keep insisting that Unit 731 was purely evil, he said, "They have to ignore what their side did."

He added that Beijing's government regularly revives the 731 narrative when Japan debates constitutional reform or defense policy. "Every time Japan moves toward strengthening its military posture, the Chinese media bring up Unit 731 again," he said. "It's part of a political script."

Beyond Absolute Evil

Hironaka acknowledged that terrible things were committed under the banner of research. But he argued that most foreign and domestic discussions treat Unit 731 as an "absolute evil" detached from historical context.

Western scholars, he said, often link the unit with Auschwitz. "But 731 was not created with the intent to exterminate the Chinese," he explained. "It was established as part of Japan's preparations for a possible war against the Soviet Union."

That difference, he warned, matters. When scholars begin with moral condemnation, they inevitably distort analysis. "Because they assume Japan is entirely at fault," he said, "they stop trying to understand. Everything becomes an extension of that assumption."

Western Misconceptions

According to Hironaka, the most persistent misunderstanding in Western scholarship is the assumption that Japan's wartime conduct was centrally planned and ideologically driven. "Many think Japan had a systematic plan to exterminate Chinese civilians," he explained. "But Japan's war was chaotic, improvised, often without clear orders."

He added that foreigners frequently overestimate Japan's wartime efficiency. "They imagine everything was part of a grand design," he said. "That's not how Japan operates, even today. We improvise, we make mistakes, and sometimes we act without strategy."

For him, this misconception stems from equating Japan's crimes with Nazi genocide. "I'm not saying Japan was innocent," he emphasized. "But the nature of its wrongdoing was different. To understand that difference is essential for real historical study."

America's Secret Bargain

Asked why the United States negotiated with Unit 731 members despite Japan's unconditional surrender, Hironaka said the answer was pragmatic. "The Americans wanted to use the experimental data," he said. "If they formally recognized Shiro Ishii and the others as war criminals, they couldn't use it. So they made a secret deal: receive the data, and declare them not guilty."

He believes Cold War urgency drove those decisions. "The Soviets were already interrogating captured Japanese personnel in Siberia," he said. "America had to act quickly, not just to learn what happened, but to keep Moscow from benefiting first."

Even today, he noted, some of that data continues to influence medical research. The 731 data were later used in vaccine development for cholera, plague, and influenza.

Hironaka called this moral contradiction unavoidable but troubling. "Scientific progress cannot justify the violation of human rights," he said. "If we say anything is acceptable in the name of discovery, we lose our humanity."

Lost Archives and Hidden Records

Hironaka explained that Japan still lacks a full picture of Unit 731 because most original files were destroyed at the war's end. After the surrender, the Soviets held the Khabarovsk Trials, and the US GHQ conducted interrogations recorded in the Sanders and Perl reports. "Those documents are public, but many others remain sealed," he noted.

According to him, the US returned a trove of materials to Japan in the late 1960s, which are now stored in the National Institute for Defense Studies. "They were returned but not released," he said. "Researchers sued for disclosure, and only a small portion has been opened. The rest remains off-limits."

That secrecy, he warned, fuels both denial and exaggeration. "The longer the records stay hidden, the easier it becomes for both sides to claim whatever they want," he said. "Transparency is the only way to stop that."

At the same time, he stressed that history must not become a weapon. "Self-examination is a moral duty," he said, "but allowing others to manipulate that guilt is not."

When asked whether it took courage to research such a controversial subject, Hironaka replied, "If you keep pursuing the facts wherever they lead, there’s nothing to fear."

Author: Daniel Manning