Japan dropped balloon bombs, or fusen bakudan, into the Pacific jet stream on November 3, 1944. They each carried a thirty-pound high-explosive bomb and four incendiaries. The balloon bombs, Japan's most recent weapon, were designed to cause harm and create terror throughout the United States. On May 5, 1945, the balloons would kill six Americans, although they were universally regarded as a military disaster. In April 1945, Japan called an end to the activity.
In 1933, the Japanese Military Scientific Laboratory came up with the concept of balloon bombs. According to Robert Mikesh, their Proposed Airborne Carrier research and development programme investigated a number of concepts, including the original concept of balloon bombs. His academic study of these Fu-Go balloons is a seminal piece on this elusive subject.
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