Chinese film 'Evil Unbound' revives Unit 731 atrocities as Japan-China tensions escalate

In the summer of 1945, as Japan faced defeat, soldiers at a military facility in occupied Manchuria received an order: bury the evidence. A 14-year-old boy named Hideo Shimizu, drafted into service only months earlier, was among those sent to the prison compound to inter charred bones in the dirt. He had arrived in Harbin expecting factory work. Instead, he had been shown a room on the second floor of a laboratory building, its shelves lined with glass jars containing severed human limbs preserved in formalin. Some jars stood as tall as a man. Inside them were the remains of children—ten, twenty, perhaps more—and the corpse of a pregnant woman, her fetus still visible where her skin had been flayed away. This was Unit 731, the covert research division of the Imperial Japanese Army, and what Shimizu witnessed in those six months would haunt him for the next seventy years.

Unit 731 operated between 1936 and 1945 as a sprawling complex of 150 buildings in Harbin, disguised first as a lumber mill, then as a water purification plant. Its official name was the Epidemic Prevention and Water Purification Department of the Kwantung Army. In reality, it was a systematic engine of human destruction. The facility's leadership—headed by Lieutenant General Shiro Ishii, an ultra-nationalist microbiologist who enjoyed the blessing of Emperor Hirohito—subjected thousands of prisoners to live dissection without anesthesia, deliberate infection with bubonic plague, typhus, and cholera, and grotesque experiments in frostbite treatment. Victims were called "maruta," or logs—a linguistic erasure that rendered them subhuman in the eyes of their torturers. At the headquarters alone, approximately 14,000 people were murdered, 3,000 of them through vivisection. Scholars estimate that between 250,000 and 500,000 civilians from surrounding villages died through the deliberate contamination of water supplies, food, and agricultural land with pathogens the unit had engineered. The victims were predominantly Chinese, though Korean, Russian, British, and American prisoners of war were also subjected to the unit's experiments. Pregnant women, raped by guards, were dissected alive. Children were given chocolates laced with anthrax and biscuits infected with plague. Men were deliberately infected with syphilis and then forced to rape other inmates so doctors could observe disease transmission. Limbs were amputated and organs removed, then reattached in the wrong places to study the effects. Prisoners were used for flamethrower practice, forced into low-pressure chambers until their eyeballs burst, injected with animal blood before being cut open alive.

When Japan surrendered in August 1945, Ishii ordered the demolition of the headquarters to destroy evidence of the crimes. All surviving prisoners were murdered and buried. The soldiers and technicians of Unit 731 were given cyanide compounds and ordered to take their own lives rather than be captured by Soviet forces. But the destruction was incomplete. In 2023, Chinese archaeologists excavated a U-shaped underground bunker near the city of Anda, measuring 108 feet long and 67 feet wide, built in 1941 as a test site for the unit's most sadistic experiments. The Ping Fan headquarters, now a museum, still contains rows of cages that once housed giant rats used to produce bubonic plague. The plague-carrying fleas were later dropped on villages as part of biological warfare experiments. The unit produced 300 kilos of plague bacteria every month, 500 kilos of anthrax, and nearly a tonne of dysentery and cholera—enough, by some estimates, to slaughter every human being on earth many times over.

At the war's end, the United States made a secret bargain with Unit 731's leadership. In exchange for access to the unit's research data, American authorities granted immunity to the perpetrators. Ishii was never tried for his crimes. He died of cancer in 1959. Other members of Unit 731 went on to become high-ranking officials in the Japanese government and medical profession. The Japanese government has never apologized for Unit 731's actions and insists it has found no evidence that the unit experimented on Chinese prisoners. In 1997, a professor named Saburo Ienaga won a 32-year legal battle against Japan's Ministry of Education after the Supreme Court ruled that the censorship of school textbooks was unlawful—he had written about Unit 731 and the Nanjing Massacre, and the ministry had demanded those passages be deleted. In 2002, a Japanese court rejected compensation claims from 180 Chinese victims of wartime biological warfare, though the three judges did acknowledge the facts of the case—the first time a Japanese court admitted Japan had conducted biological warfare during World War Two.

Seventy years after the war ended, Shimizu began to speak. Now 95, he started delivering lectures about what he had witnessed, driven by the sight of photographs of his grandchildren and great-grandchildren—faces that reminded him of the victims he had seen in the slaughterhouse. "There were ones that had been sliced in two vertically, so you could see their organs," he said. "I was dumbfounded. I thought: 'How could they do this to a small child?'" For his honesty, Shimizu has been subjected to relentless abuse on Japanese social media. People call him a senile liar, a public nuisance. "If you say something did not happen 100 times, it becomes as if it really never did," he told a reporter from the Asahi Shimbun. "That is frightening." He appeared exhausted. "I am getting tired these days. This might be the last time," he said of his public speaking.

Other witnesses have also broken their silence. A former medical assistant at Unit 731, a farmer in his seventies who requested anonymity, described to the New York Times in 1995 the first time he performed a vivisection. "The fellow knew that it was over for him, and so he didn't struggle when they led him into the room and tied him down," he said. "But when I picked up the scalpel, that's when he began screaming. I cut him open from the chest to the stomach, and he screamed terribly, and his face was all twisted in agony. He made this unimaginable sound, he was screaming so horribly. But then finally he stopped." A nurse named Toyo Ishii, who worked at a medical school in western Tokyo, came forward decades later with evidence that workers had been ordered to bury dozens of bodies at the site after Japan's surrender. "We took the samples out of the glass containers and dumped them into the hole," she wrote in a statement in 2006. "We were going to be in trouble, I was told, if American soldiers asked us about the specimens."

This December, a new Chinese film called "Evil Unbound," directed by Linshan Zhao, brought these atrocities to the screen. The movie follows a fictional prisoner named Wang Yongzhan as he discovers torture laboratories and a crematorium within the prison compound and leads an escape. The trailer shows hooded prisoners stripped naked, bloodied medical tools, patients screaming as doctors crowd around them, victims flailing as they are forced to bathe their hands in toxic chemicals. A commander's voice says: "Once we've used up these logs, just get some more." The film makes no effort to soften what occurred. Before its theatrical release in China on September 18, the Japanese embassy issued a security advisory warning Japanese nationals to be "vigilant against anti-Japanese sentiment" due to films and events marking the 80th anniversary of the war's end. The film's debut was postponed from its original July 31 date, sparking speculation in Japanese media that the delay was intended to avoid diplomatic tensions. When the film finally released, China Central Television reposted the trailer on Weibo with the message: "The truth cannot be forgotten." State media praised the film as a "history lesson Japan must not miss." Another recent Chinese film, "Dead to Rights," depicts the Nanjing Massacre of late 1937, in which the Japanese army killed more than 300,000 civilians and soldiers and allegedly raped around 20,000 women.

These films have arrived at a moment of escalating tension between China and Japan. Over the summer, Tokyo called on Beijing to ensure the safety of Japanese nationals after reports of increased violence between the two nationalities. A Japanese woman and her child were attacked in a Suzhou underground station on July 31. The Chinese embassy in Japan reported that two Chinese men were seriously injured in an assault by four unidentified men in Tokyo on the same day. Military tensions have reached their highest level in more than a decade, exacerbated by disputes over Taiwan. Prime Minister Sanae Takaichi said a Chinese attack on the self-governed island could create a "survival-threatening situation" for Japan, and Japan's self-defence forces could be activated to respond. As the year ends, the two nations are locked in an increasingly bitter war of words, while civilians on both sides reckon with historical wounds that refuse to heal. The past, it seems, is not past at all.