Sworn to secrecy by the Japanese Imperial Army, Hideo Shimizu carried the horrors he saw at the notorious Unit 731 facility with him for more than 70 years.
The 93-year-old was just 14 when he was drafted as a cadet to the city of Harbin, in what was then Japanese-occupied Manchuria, during World War II.
There, he was groomed to take part in some of history’s worst atrocities – human experiments carried out on prisoners of war including pregnant women and small children.
More than 3,000 people – mostly Chinese civilians, but also Russian, British and American POWs – were dissected alive, infected with bubonic plague and used as human guinea-pigs for frost-bite treatments in nightmarish torture laboratories.
Decades on, innocent pictures of his grandchildren and great-grandchildren reminded Shimizu of the faces of the many victims he came across in the slaughterhouse.
The veteran realised that he had to break his silence for the sake of the next generation.
Now a retired architect who built an comfortable life for himself and his family, Shimizu tried to bury his dark past, not even revealing it to his closest relatives.
But the memories of his former life came flooding back when he and his wife visited a war museum back in 2015.
He was unable to contain his emotions when he saw a photo among the relics of a large brick building – the Epidemic Prevention and Water Purification Department of the Kwantung Army, or Unit 731.
He found himself telling his wife everything he knew about the building, and finall admitted that his knowledge was first-hand as he had been a member of the biological warfare unit himself.
Unit 731 was built in 1936 in modern-day Harbin, northeastern China, for the Japanese Imperial Army to conduct research into germ warfare, weapons capabilities and the limits of the human body.
The covert operation was run originally under the guise of a lumber mill, then a water purification plant.
While it was human flesh rather than lumber the sick scientists were cutting up, they dehumanised their victims by referring to them in Japanese as ‘marutas,’ or wooden logs.
‘So many ‘marutas’ died, and the Japanese soldiers were also dissected. I often wonder why on earth Unit 731 had done so many evil things?’ Shimizu said.
He was recruited into the unit’s ranks at the end of March 1945, just a few months before the war ended, to serve as a ‘technician on probation.’
A picture remains of Shimizu as a teenage cadet in uniform alongside his comrades when he joined up.
His former teacher had encouraged him to take up the work due to his aptitude for arts and crafts.
‘I knew nothing about what the army was or what it did specifically,’ he said in a recent interview.
He expected he would be sent to a factory, but instead, he and five other boys from his village were packed off on a train to China to start work in Unit 731’s laboratories.
He says he still has nightmares even now about the day in July 1945 when he was taken to a specimen room inside the auditorium on the second floor of the building.
The room was lined with jars, he said, some as tall as an adult – each containing human body parts preserved in formalin.
‘There were ones that had been sliced in two vertically, so you could see their organs,’ Shimizu said.
‘There were children; ten or twenty of them, perhaps more. I was dumbfounded. I thought, ‘how could they do this to a small child?’
It was the first time Shimizu had seen corpses, and he couldn’t stop crying, while the person who took him on the tour said nothing.
‘I think they took me there because they wanted to see my reaction to the sight of the logs. All I could think of was, ‘what will they make me do?’ he said.
Shimizu soon realised that he was being trained to carry out dissections himself.
Thankfully, the child soldier was saved by the course of the war – which would end abruptly weeks later with Japan’s surrender.
Three days after the atomic bomb was dropped on Nagasaki, Shimizu was called to the camp prison, morbidly dubbed the ‘log cabin’, to bury the burnt bones of murdered inmates in an effort to conceal the unit’s crimes.
Soviet forces invaded the former Manchuria in August, and he and other members of the unit retreated back to Japan.
The soldiers and technicians were given a cyanide compound and ordered to kill themselves rather than be captured.
After he returned to Japan, Shimizu never talked about what he saw or heard at the murder camp.
Today, the site, now a museum, echoes many of the chilling hallmarks of a former Nazi death camp with its disused railway track and ghostly buildings.
One structure still today contains rows of cages that housed giant rats which Japanese doctors used to produce the bubonic plague.
The horrendous disease was later unleashed on hundreds of thousands of Chinese, by dropping plague-carrying fleas on villages as part of experiments in biochemical warfare.
Photographs from the book Unit 731: Laboratory of the Devil, Auschwitz of the East shows Japanese soldiers taking part in a vivisection – carrying out operations on a live person to study living tissue and organs.
Despite the overwhelming evidence of the Japanese Imperial Army’s crimes – as well as cover-ups by the US and others – many in Japan still refuse to believe Shimizu.
He received abuse online from right-wing nationalists who refused to accept that Japanese troops could have behaved in such a shameful way.
‘This old biddy is telling lies… Either that, or he doesn’t exist,’ one conspiracy theorist wrote.
Responding to their claims, Shimizu told The Asahi Shimbun newspaper: ‘They don’t know what horrible things Japan did to people in another country.
‘No matter what people say to me, I must keep telling the truth, otherwise future generations will be deprived of a chance to learn about it.’