A museum documenting the wartime atrocities of the Japanese Imperial Army has released video testimony from a former member of Unit 731, providing a rare and graphic account of the team's biological warfare research and human experimentation during World War II.

The Exhibition Hall of Evidences of Crime Committed by Unit 731, located in Harbin, Heilongjiang province, released the recording of Hideo Sato, a former member of the unit's plague research squad.

In the 47-minute video, Sato details the cultivation of plague bacteria, animal dissections, and the systematic use of human subjects to develop biological weapons. The video was recorded in the 1990s by Japanese scholar Fuyuko Nishisato and donated to the museum in 2019.

Sato served in the unit from March 31, 1942, to March 31, 1945. He described his primary role as verifying the lethal dose and mortality rates of plague bacteria.

"I personally dissected thousands of rats, guinea pigs, and other animals," Sato said. "The animals' livers and pancreases turned black and enlarged after being infected with plague bacteria. My work was aimed at turning the plague bacteria into a weapon."

Sato's testimony confirms that experiments were conducted on living test subjects, whom the Japanese referred to as "marutas". These prisoners were held in heavily guarded, enclosed special prisons.

"They were provided with adequate nutrition because unhealthy individuals could not be used as experimental subjects," Sato said.

He noted that the unit maintained a strict hierarchy, where only experienced members were permitted to conduct live human experiments.

Jin Shicheng, director of the museum's education and publicity department, said Sato's account corroborates historical archives regarding the unit's extreme secrecy and structure.

"Unit 731 was also known as the 'rat unit' due to their large-scale capture of rats to breed fleas for producing biological weapons," Jin told China Central Television. The plague-infested fleas were designed for maximum lethality against both military and civilian populations.

The testimony also sheds light on the manufacturing scale of the operation. Sato described facilities where bacteria were propagated in culture tanks within greenhouses set to 37 C for 24 to 48 hours.

"The propagated bacteria could be spread by aircraft or made into solid forms to contaminate water sources," Sato said.

According to Jin, the unit was staffed by the "elites" of the Japanese medical community, including more than 200 doctors and scientists from top universities who participated in live dissections.

Museum officials say the release of this testimony supplements the existing body of evidence, which includes archival materials and site artifacts.

"It further confirms that Unit 731's biological warfare was a large-scale, organized group crime from top to bottom in Japan," Jin said.

Unit 731 functioned as the nerve center for Japan's biological and chemical warfare in China and Southeast Asia.

Historical estimates suggest that at least 3,000 people were killed in direct experiments, while more than 300,000 people across China died as a result of the biological weapons deployed by the unit.