the US struck a secret agreement with Ishii. In a memo to General Douglas MacArthur (1880 – 1964), commander of Allied forces in Japan, Washington recognized that although war crimes had been committed, the experiments led by Ishii and his colleagues were “almost incalculable and incredibly valuable to the United States.”
In exchange for the records of Unit 731’s experiments, the US granted Ishii and his assistants immunity. Ishii died, and his collaborators went on to have careers in prestigious universities and private laboratories.
Not to mention there was often no method or recorded data, so even calling them “science” of any kind is doubious.