Operation PX, also known as Operation Cherry Blossoms at Night, was a planned Japanese military attack on civilians in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

using

biological weapons A biological agent (also called bio-agent, biological threat agent, biological warfare agent, biological weapon, or bioweapon) is a bacterium, virus, protozoan, parasite, fungus, or toxin that can be used purposefully as a weapon in bioterrorism ...

, devised during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...

. The proposal was for

Imperial Japanese Navy The Imperial Japanese Navy (IJN; Kyūjitai: Shinjitai: ' 'Navy of the Greater Japanese Empire', or ''Nippon Kaigun'', 'Japanese Navy') was the navy of the Empire of Japan from 1868 to 1945, when it was dissolved following Japan's surrend ...

submarines to launch

seaplanes A seaplane is a powered fixed-wing aircraft capable of taking off and landing (alighting) on water.Gunston, "The Cambridge Aerospace Dictionary", 2009. Seaplanes are usually divided into two categories based on their technological characteris ...

that would deliver weaponized bubonic plague, developed by

Unit 731 , short for Manshu Detachment 731 and also known as the Kamo Detachment and Ishii Unit, was a covert Biological warfare, biological and chemical warfare research and development unit of the Imperial Japanese Army that engaged in unethical h ...

of the

Imperial Japanese Army The was the official ground-based armed force of the Empire of Japan from 1868 to 1945. It was controlled by the Imperial Japanese Army General Staff Office and the Ministry of the Army, both of which were nominally subordinate to the Emperor o ...

, to the

West Coast of the United States The West Coast of the United States, also known as the Pacific Coast, Pacific states, and the western seaboard, is the coastline along which the Western United States meets the North Pacific Ocean. The term typically refers to the contiguous U.S ...

. The operation was abandoned shortly after its planning was finalized in March 1945 due to the strong opposition of General

Yoshijirō Umezu (January 4, 1882 – January 8, 1949) was a Japanese general in World War II and Chief of the Army General Staff during the final years of the conflict. He was convicted of war crimes and sentenced to life imprisonment. Biography Early life a ...

, Chief of the Army General Staff.

Overview

Operation PX was proposed in December 1944 by the Japanese Naval General Staff, led by Vice-Admiral Jisaburō Ozawa. The name for the operation came from the Japanese use of the code name PX for Pestis bacillus-infected fleas. In planning the operation, the navy partnered with Lieutenant-General

Shirō Ishii Surgeon General was a Japanese microbiologist and army medical officer who served as the director of Unit 731, a biological warfare unit of the Imperial Japanese Army. Ishii led the development and application of biological weapons at Unit 73 ...

, who had extensive experience on weaponizing pathogenic bacteria and human vulnerability to biological and chemical warfare. The plan for the attack involved ''Seiran'' aircraft launched by

submarine aircraft carriers A submarine aircraft carrier is a submarine equipped with aircraft for observation or attack missions. These submarines saw their most extensive use during World War II, although their operational significance remained rather small. The most fa ...

upon the West Coast of the United States—specifically, the cities of San Diego, Los Angeles, and San Francisco. The planes would spread weaponized bubonic plague, cholera,

typhus Typhus, also known as typhus fever, is a group of infectious diseases that include epidemic typhus, scrub typhus, and murine typhus. Common symptoms include fever, headache, and a rash. Typically these begin one to two weeks after exposure. ...

, dengue fever, and other pathogens in a biological terror attack upon the population. The submarine crews would infect themselves and run ashore in a suicide mission. Planning for Operation PX was finalized on March 26, 1945, but shelved shortly thereafter due to the strong opposition of Chief of General Staff

. Umezu later explained his decision as such: "If bacteriological warfare is conducted, it will grow from the dimension of war between Japan and America to an endless battle of humanity against bacteria. Japan will earn the derision of the world." A final planned use of the biological weapons came just after the surrender of Japan, as Shirō Ishii planned to stage suicide germ attacks against U.S. occupation troops in Japan. This planned attack never took place either, due to opposition from Yoshijirō Umezu and Torashirō Kawabe, who did not want Ishii to die in a suicide attack, and asked him to instead "wait for henext opportunity calmly". After the war, Operation PX was first discussed in an interview by former captain Eno Yoshio, who was heavily involved with planning for the attack, in an interview with ''Sankei'' on August 14, 1977. According to Yoshio, "This is the first time I have said anything about Operation PX, because it involved the rules of war and international law. The plan was not put into actual operation, but I felt that just the fact that it was formulated international misunderstanding. I never even leaked anything to the staff of the war history archives at the Japanese Defense Agency, and I don't feel comfortable talking about it even now. But at the time, Japan was losing badly, and any means to win would have been all right."Gold, page 89

References

{{Reflist PX PX American Theater of World War II Military history of Japan during World War II Japanese war crimes 1945 in Japan Japanese biological weapons program