Unit 731's canceled attack on the US: War's close call

Unit 731, infamous for brutal experiments, planned a biological attack on the USA. Operation PX was to be executed using biological weapons, which could have changed the course of the war. The plan involved using infected fleas and suicide soldiers.

Unit 731, operating in occupied Manchuria, was responsible for cruel experiments on Chinese civilians and prisoners of war. Between 1932 and 1945, at least 270,000 people died there. The experiments included testing anthrax, cholera, and plague.

In the town of Anda, a testing ground was created where biological bombs, called porcelain bombs, were developed and tested. There are suspicions that the Japanese unit might have also been present in Siam, known today as Thailand. The overall operations of these facilities were supervised by the Epidemiological Research Laboratory, whose main headquarters was in Tokyo.

Japanese military authorities showed little interest in adhering to the Geneva Protocol, which prohibited the use of biological and chemical weapons during warfare. Microbiologist Shirō Ishii, head of Unit 731, believed that the prohibitions on weapons only confirmed their high effectiveness in military actions.

Brutal experiments were conducted on prisoners using pathogens such as anthrax, cholera, and plague. Pure air was injected intravenously, and various substances, including animal urine, were introduced into the kidneys. They were also exposed to toxic phosgene and radioactive substances. In extreme cases, pregnant women were forced to give birth to live fetuses via surgical incisions.

Operation PX, known as "Cherry Blossoms at Night," was to be a combination of biological weapons raids and kamikaze attacks. The plan involved using I-400 ships, which could transport airplanes capable of spreading microbes on the West Coast of the USA.

According to various sources, the displacement of this ship ranged from 3,530 to 6,560 tons, and its speed on the surface could reach 21 mph. The speed it developed underwater was 7 mph. Thanks to special technical solutions, its diesel engines could operate even when the vessel remained submerged.

The I-400, at a surface speed of 18 mph, could travel up to 35,700 miles, and this range could be increased if needed. Such capability allowed the vessel to easily reach the United States, located about 6,300 miles from the Japanese home islands. However, the presence of powerful Allied forces in the Pacific meant that the ship would have had to travel most of the route submerged, which significantly lengthened the travel time.

Despite advanced preparations, the operation was halted by Gen. Yoshijirō Umezu. He feared that biological warfare would escalate the conflict between Japan and the USA, becoming a global threat.

After the war, Unit 731's documentation ended up in American hands, allowing Japanese medics to avoid punishment. The Soviets condemned this fact, fearing the technological advantage of the USA. General Umezu, despite being recognized as a war criminal, showed more moral dilemmas than his opponents.

In a secret report that came to light in 1947, thanks to the head of US Navy intelligence, there was a significant remark. The report suggested that there is no certainty that humanitarian considerations will ever stop humanity from deliberately causing an epidemic.