We’ve already brought you the story about Unit 731, the Japanese germ warfare division that worked for more than ten years to weaponize some of the worst diseases that have ever afflicted mankind, but you may not have the sheer scope of the project in view.
Founded in 1931 as a normal army medical unit, by 1935 the team was stockpiling supplies of bubonic plague, anthrax, and cholera in forms that were distressingly easy to deploy against civilians.
In just a single attack in Manchuria, the Japanese dropped aerial bombs filled with sawdust and plague-infected fleas over population centers. This was partly a terror bombing against territory that the Japanese already controlled, and partly a test of the weapon’s effectiveness.
When the bomb casings split open in the air, the fleas fell unharmed to the ground and began biting people, infecting their blood with a strain of Yersinia pestis that had been bred for greater virulence by being passed through multiple generations of Chinese and Korean prisoners.
Poring over population figures before and after the war, the Chinese government now estimates that this one attack may have killed nearly 600,000 people in the weeks following the drop. Unit 731’s other activities may have killed another half a million or so innocent people before the end of the war.