Unit 731: How Japan Excused Crimes Against Humanity
- David Porres
- May 31
- 3 min read
Updated: Jun 23
Unit 731 marked a dark era of Japanese war crimes. Headed by the Kwantung Army, the Mukden Incident on September 18, 1931, saw Japan begin its Manchurian campaign of conquest. From 1932 to 1945, the Japanese forces invaded and occupied Chinese Manchuria, forming the puppet state of Manchukuo. Shirō Ishii proposed the Army Ministry a secretive biological warfare research program, claiming it would be in the best interest of Japan. With a shifting far-right political landscape, his ultranationalist propositions found fertile ground. In Ishii’s eyes, the newfound colony was perfect for his experiments. The population of Manchukuo meant nothing to the Japanese Army, and Ishii was given free reign. Officially established in 1936, Unit 731 was the Japanese Imperial Army’s top-secret biological warfare research program, committing heinous experiments on human victims. Emperor Hirohito played a more direct role establishing Unit 731 than often acknowledged. While military leaders like Shirō Ishii spearheaded the program, Hirohito’s authorization of biological weapons research revealed his tacit approval; therefore, rather than being a mere figurehead, Hirohito’s influence contributed to the atrocious perpetuation of Unit 731.
Shirō Ishii was the driving actor behind Unit 731’s creation, yet its success and expansion would not have been possible without Japan’s wartime political and military landscape. The program’s scope was massive – over 20,000 Japanese professionals worked within Unit 731, demonstrating the extent of its integration into the military machine. While Japan functioned as a constitutional monarchy, with much of the government controlled by the parliamentary and military elite, Hirohito’s influence cannot be ignored. He was the “Supreme Ruler” in whose name all military actions were carried out, the heart of the Japanese people. In 1936, Hirohito issued an imperial decree to expand Unit 731, officially integrating it into the Kwantung Army. His approval of bacteriologic weapons research, as well as his consistent authorization of warfare as “an acceptable means to an end,” indicates a level of complicity. While some historians argue that Hirohito lacked control over military decisions, his active role in suppressing uprisings demonstrates that he was not merely a powerless figurehead. Hirohito’s tacit approval of biological warfare aligned with the broader ultranationalist ideology that dominated Japan. Ishii’s rhetoric of Unit 731 as a critical military asset found support with the far-right government, reinforcing Japan’s expansionist ambitions and further solidifying Hirohito’s role in wartime atrocities. However, Hirohito was not the sole driving force. The Imperial Japanese Army rose to immense power in the 1930s, practically controlling the state. The Kwantung Army, in particular, often operated without approval from Tokyo. However, while Hirohito may not have directly overseen Unit 731, he made no significant attempts to stop it, even when the Geneva Protocol had specifically outlawed biological warfare, let alone the torture of prisoners. Ultimately, while the militarist government exercised considerable authority, his authorization of Unit 731’s expansion, tolerance of chemical warfare, and alignment with ultranationalist ideologies suggest that he was more than a passive bystander. Rather, Hirohito’s leadership contributed to Japan’s embrace of crimes against humanity, highlighting a shameful period in Japanese history.
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