The military use of the Jet Stream by the Japanese during World War II

When the Japanese discovered the Jet Stream, it was for military use. And with good reason: The Japanese Empire is at war, and its resources are limited. In 1942, they are on the defensive and prepare a bad surprise to the Americans: they send them balloons loaded with explosives. A silent “invasion” begins.

When the Japanese discover the Jet Stream, it is to make a military use of it. And with good reason: The Japanese Empire is at war, and its resources are limited. In 1942, they are on the defensive and prepare a bad surprise to the Americans: they send them balloons loaded with explosives. A silent “invasion” begins.

November 1941, relations between Japan and the United States deteriorate. The United States asked the Japanese to withdraw from China and Indochina, which they had recently occupied. The Japanese wanted the Americans to lift their embargo on steel and oil and to stop supporting China. That is the impasse. On the 26th of the same month, the Americans demand that the Japanese withdraw from the Axis. But they refused and took this demand as an ultimatum. On December 7th, the Japanese air force ravages the military port of Pearl Harbor and destroys the 8 battleships that are there. Logically, the United States declared war on them, but suffered setbacks throughout the Western Pacific. From the winter of 1941 to the spring of 1942, the Japanese advance was dazzling. It was halted by the Americans during two major battles: the Coral Sea and Midway on 4 June 1942. The Japanese were already on the defensive six months after the start of hostilities. Then begins an incredible enterprise of demoralization against the Americans: the Fugo project.

The Yorktown in trouble at Midway, before being torpedoed

This project consists of dropping balloons on the United States. These unmanned balloons are loaded with incendiary and explosive bombs. A special mechanism is designed to lower them and set off the explosion. These explosions must cause large forest fires, in order to divert manpower and create panic among the population. The balloons are produced by artisanal factories. The envelope is made of rice paper and the glue is made from potatoes. These explosive devices are launched from the island of Honshu. Except the west coast of the United States is 10,000 km away. How do we solve the problem of distance? Actually, the Japanese use the Jet Stream. These are very violent winds that surround the earth, organized in narrow tubes and are located about ten kilometers above the ground. These winds, which pass over Japan, carry the balloons which then travel all over the Pacific at an average speed of 300km/hour. Then, by an adjustment, the devices descend and explode in American territory. The idea is simply brilliant and the Americans are disarmed in the face of the Japanese ruse.

A Fugo balloon In six months, from November 1944 to April 1945, Japan dropped 9,300 of these aerostats. But because of a manufacturing defect, only a small number of these balloons (less than 500) arrived in North America. Japanese balloon bombs were a real worry. Everybody at the factory was always looking up because of the statistical chance that one of them would fall. I remember seeing 40 of them go by at one time. The Navy in Pasco regularly chased them away but they were not very successful. Matthias and I went to tarabuster them for better protection. They never managed to shoot one of them down, although a number of them went down on the project grounds, but away from the buildings. The bombs never exploded, but the balloons were flying around and the soldiers put on a good show trying to catch them without blowing themselves up.” – Testimony of Walter O. Simon.
These balloons have caused only anecdotal damage*. In spite of this, the United States instituted censorship, to avoid panic and also so that the Japanese would not know that their balloons had reached their target. Nevertheless, the public was completely unaware of the danger: on May 5, 1945 schoolchildren and their teacher, who handled a bomb, were killed. But this silence made the Japanese believe that the project had failed and stopped it in April 1945.

On March 10, 1945, one of the last Fugo balloons launched, descended towards Hanford, Washington. The balloon hit a power line and shut down the Hanford nuclear reactor for three days. This reactor was part of Manhattan’s Top Secret Project, producing plutonium for the bomb that, 5 months later, was dropped on Nagasaki.

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The United States and the world since 1945