Japanese Media Reveals WWII Animal Blood Transfusion Tests

Japan’s leading news agency, Kyodo News, has uncovered official records from the Imperial Japanese Army documenting that military medical officers conducted “heterologous blood transfusion” experiments during the Sino-Japanese War, injecting horse, sheep, and dog blood into 23 human subjects. The discovery, published on June 20, 2026, provides direct documentary evidence of institutionalized medical atrocities that add to the extensively documented history of Japanese wartime medical crimes, including those of Unit 731.

The Discovery

According to Kyodo News, the records were found in the official journal of the “Army Medical Corps” (陸軍軍医団), a public organization, preserved at Japan’s National Diet Library. The experiments were reported at the March 1940 “Army Military Medicine and Pharmacy Research Conference” by an instructor from the Army Medical School in Tokyo, who claimed the research was conducted under the pretext of studying battlefield blood loss treatment where securing sufficient human blood for transfusion was difficult.

The instructor reported that during the “current incident” — referring to the Sino-Japanese War that began in 1937 — his team had “experienced many cases of transfusion using animals as blood sources.” The experiments took place in autumn 1938, but the location was redacted in the original document, suggesting military censorship. The experiments are suspected to have been carried out in China.

The Experiments

The 23 subjects, whose identities and attributes remain unknown, were subjected to multiple unethical procedures. According to the Kyodo report, these included massive transfusions of horse blood into subjects in critical condition after blood loss — a procedure considered beyond common sense due to the near-certainty of fatal immune rejection. Additional experiments involved injecting chicken blood into subjects to observe retention time, and surgically stopping neck blood flow before serum injection, a procedure unrelated to any therapeutic purpose.

Sing Tao Daily reported that the animal blood used included horse blood, sheep blood, and dog blood. The report noted that subjects developed high fever after the transfusions, and the procedures were described as clearly violating medical ethics.

The conference where these findings were presented was attended by the Army Ministry Medical Bureau Chief, numerous military medical officers, and pharmaceutical officers, indicating institutional knowledge and approval of the experiments.

Historical Context: Unit 731 and Medical Atrocities

This revelation adds to the documented history of Japanese wartime medical atrocities, most infamously associated with Unit 731, a covert biological and chemical warfare research unit of the Imperial Japanese Army established in 1936 in Harbin, Manchuria. Under the command of General Shirō Ishii, Unit 731 conducted lethal human experiments including vivisection without anesthesia, frostbite experiments, and biological weapons testing involving plague, anthrax, cholera, and typhoid on human subjects. An estimated 3,000 to 12,000 people — mostly Chinese, but also Russians, Koreans, Mongolians, and Allied prisoners of war — died as a result.

After the war, the United States granted immunity to Unit 731 researchers in exchange for their biological weapons data, a decision that remains highly controversial. The Japanese government has been criticized for not fully acknowledging or apologizing for these war crimes.

While these newly revealed experiments were conducted by the Army Medical School rather than Unit 731 specifically, they demonstrate that unethical human experimentation was widespread within the Japanese military medical establishment, not confined to a single unit.

Significance and Implications

The Kyodo News investigation is significant because it represents internal Japanese accountability efforts rather than external accusations. The fact that these records were preserved in an official publication of the Army Medical Corps — rather than relying on survivor testimony or post-war investigations — provides direct institutional evidence of the experiments.

Xinhua News reported that Chinese historians have called for Japan to thoroughly reflect on its wartime aggression and atrocities, including human experimentation. The Chinese government has consistently called for Japan to acknowledge and apologize for its wartime crimes.

Questions That Remain

Several questions remain unanswered. The name of the Army Medical School instructor who conducted and reported the experiments has not been disclosed. The precise location of the experiments was redacted, suggesting continued censorship. The fates of the 23 subjects are unknown, and it remains unclear whether they were Chinese civilians, prisoners of war, or Japanese soldiers. The Kyodo report suggests that other documents may still exist in the Army Medical Corps journal and other archives.

What’s Next

This discovery adds pressure on Japan to fully acknowledge its wartime medical atrocities and may affect bilateral relations with China, which has long called for Japan to confront its wartime history. The revelation also highlights the ongoing importance of archival research in uncovering historical truths, even eight decades after the events. Japanese researchers, journalists, and civil society groups continue to gradually uncover evidence of wartime medical atrocities, contributing to a fuller historical record.