Unit 731. There are a number of books with this title, but I think this is the one I read. This was one of Japan's human-experimentation groups during WWII, located in Harbin, China. What went on there was horrific beyond words. But it's not all that well known in the west.
https://www.amazon.com/dp/B005M2AHZO/?tag=2849060093-20 this is the primary source I used in my class. It was very good for most of the accounts and is what Wikipedia uses for the detailed accounts.
https://www.youtube.com/watch?v=UQB3fnoQVsA this is (garbagely made) movie about it. The acting is bad, but it has a good premise.
https://www.youtube.com/watch?v=akLVQdVyGMk this is also a sorta primary source where the soldiers talk about it.
There are also museum exhibits in Harbin that show it, if you want to see that.
You can read some of it here
> The task force now needed justification for refusing to prosecute. First they concluded that the evidence available was insufficient to document legal guilt. This was fallacious, both because it misrepresented the evidence then documented in Adjutant General reports, and also ignored the fact that confirmatory evidence was not being pursued specifically in response to military orders. Finally, the task force appealed to the same reasoning in the scientific reports: “The value to the U.S. of Japanese [biological warfare] data is of such importance to national security as to far outweigh the value accruing from ‘war crimes’ prosecution.” This conclusion amounted to a major coup for Ishii. When the full assessment of the Japanese data was finally completed, the Camp Detrick staff learned virtually nothing beyond what the Americans had already discovered by more “scrupulous” means.
And more of it here
>This review of the Dachau hypothermia experiments reveals critical shortcomings in scientific content and credibility. The project was conducted without an orderly experimental protocol, with inadequate methods and an erratic execution. The report is riddled with inconsistencies. There is also evidence of data falsification and suggestions of fabrication. Many conclusions are not supported by the facts presented. The flawed science is compounded by evidence that the director of the project showed a consistent pattern of dishonesty and deception in his professional as well as his personal life, thereby stripping the study of the last vestige of credibility. On analysis, the Dachau hypothermia study has all the ingredients of a scientific fraud, and rejection of the data on purely scientific grounds is inevitable. They cannot advance science or save human lives.
I also highly recommend the books https://smile.amazon.com/Unit-731-Testimony-Hal-Gold-ebook/dp/B005M2AHZO/ and https://smile.amazon.com/Factories-Death-Japanese-Biological-American/dp/0415932149 for more in-depth info