The April 18, 1942, sixteen B-25 Mitchell twin-engine of the 17th Bomb Group of the U.S. Army Air Corps, commanded by General James H. Doolittle, starts from the aircraft carrierUSS Hornet, in what would be the first U.S. air raid on Tokyo, Yokohama, Nagoya, Kobe and Osaka.
If the material damage were few, the same can not be said of the impact that this mission had on the morale of citizens and the prestige of the armed forces nipónicas. It was urgent, therefore, to take retaliatory measures that restaurassem the confidence of citizens and the scrolls of the troops of the Empire, paying the enemy in the same currency, ie bombing the United States.
A task which, although not impossible, did not excel in ease of implementation. The first obstacle to overcome was the distance. No planes with flight autonomy sufficient to carry out missions against distant targets, the command nippon Nor would welcome the involvement of valuable aircraft carriers of the Imperial Army in an operation fraught with risks.
Another solution was to use submarines as a launching pad for small seaplanes, maneuver performed twice but would eventually settle for a spectacular failure. The only result of these two attacks, launched in September 1942, was a small fire in the woods of Mount Emily, in Oregon.
There remained the use of balloons. Since 1933 the Japanese army developed the technology of unmanned balloons, equipped with pumps that serve as long-range artillery. In 1943 the Japanese had already more than two hundred small balloons with a diameter of 6.1 meters and a range of 915 kilometers, designed to think about the possibilities of transport in submarine I-34 and I-35. Although the Navy had refused the idea, the Japanese Army did not abandon the project, continuing to investigate to what extent feasible the idea of bombing the United States with balloons sent from Japan (military program known as Fu-Go Program).
The studies were presented to the 9th Military Research Institute and the Meteorological Observatory in Tokyo, leaving the latter body to draw a letter of direction and strength of winds in the upper atmosphere. The results did not wait, to nine thousand feet were discovered currents of air in November and March, blowing from China, passed over Japan, crossed the Pacific, reaching, at the end of the trip, the American territory.
It was enough to dispose of a balloon capable of reaching the nine thousand meters of altitude, with a single aid of the wind - which could reach 300 kilometers per hour - hit the U.S.. It has been calculated, so what more appropriate for the diameter balloons, providing them with an automatic ballast system, allowing them to achieve and maintain optimum altitude.
The test of this balloon bombs took place on December 6, 1944 with a mill of its kind to explode near Thermopolis, Wyoming. The following month, January 1945, a plane of the U.S. Navy shot down one of these planes bomb on the Californian town of Moffett Field and eventually be collected mostly intact which allowed experts from the U.S. Navy to carry out a thorough analysis the apparatus. And there were many surprises in the wake of scrutiny after it has undergone more than 9,600 miles of travel.