Forensic geologists identified the NE coast of Japan as the…

Forensic geologists identified the NE coast of Japan as the source of the sand ballast, thus the probable launch point. American recon of the areas in early 1945 identified two of three plants producing hydrogen for the project in the vicinity of Ichinomiya, and these were destroyed by B-29s flying out of the Marianas in April 1945. With other pressing considerations, and no knowledge they were having any effect, Japan gave up on the “Vengeance Balloons.”

When folks along the West Coast went to the beach 70 years ago, they always brought home flour sacks of fine beach sand, which they dried and kept in their attic in boxes, with a shovel. Not because they kept a cat in the attic, but because fine sand was the best way to fight the magnesium firebombs the Japanese were sending over by the tens of thousands on hydrogen-filled, mulberry-paper balloons assembled by schoolgirls.

Japan released the first of these bomb-bearing balloons on November 3, 1944. It was a pretty low-tech precursor to the U.S. Army’s saturation firebombing of Japanese cities, but the balloon bombs were getting here, some crossing the Rocky Mountains and coming down in Alaska, Washington, Oregon, California, Arizona, Idaho, Montana, Utah, Wyoming, Colorado, Texas, Kansas, Nebraska, Nevada, South Dakota, North Dakota, Michigan, Iowa, British Columbia, Saskatchewan, Manitoba, Alberta, the Yukon, Northwest Territories and Mexico. One that landed near Yerington, Nevada was discovered by cowboys who cut it up and used it as a hay tarp, another by a prospector near Elko who brought it in to local authorities on his burro. In all, seven fire balloons were turned in to the Army in Nevada, Colorado, Texas, Northern Mexico, and even the outskirts of Detroit. Bits of washi paper were found in the streets of Los Angeles.

On March 10, 1945, one of the last paper balloons petered out near the Manhattan Project’s production facility at the Hanford Site, Washington, and caused a short in the power feed for the nuclear reactor cooling pumps, but backup safety devices restored power almost immediately. Two landed back in Japan but caused no damage.

Yankee Dogs Panic
Japanese propaganda broadcasts announced great fires and an American public in panic, declaring casualties as high as 10,000.

As the jet stream was largely unknown then, few Americans believed the balloons could have come directly from Japan: They must be coming from North American beaches, launched by landing parties from submarines. Wilder theories speculated that they could have been launched from German POW camps in the U.S., or even from Japanese-American internment centers.

The control system ran the balloon through three days of flight. By that time, it was likely over the U.S., and its ballast was expended. A final flash of gunpowder released the bombs, and lit a 64-foot fuse. After 84 minutes, the fuse fired a flash bomb that destroyed the balloon.

The balloon had to carry about 1,000 pounds of gear. The first balloons were made of conventional rubberized material. An order went out for 10,000 balloons made of washi paper derived from mulberry bushes that was impermeable and very tough. It was only available in squares about the size of a road map, so it was glued together in three or four laminations using edible konnyaku (“devil’s tongue”) paste. Hungry workers stole the paste and ate it. Many workers were teenage schoolgirls, who assembled the paper all over Japan. Large indoor spaces, such as sumo halls and theatres. were required for the envelope assembly. Similar, but cruder, balloons were also used by Britain to attack Germany between 1942 and 1944, but with more telling effect.

Had it been done with more insight, it could have been quite effective. That the bombs were getting here and spreading across Canada and as far as the Midwest was one of the best kept secrets of the war—until a Sunday-school teacher and several little kids were killed by one of the infernal devices in southern Oregon.

Made from high-strength, gas-proofed mulberry paper, the Japanese expected about 10% of these balloon bombs to make it across the ocean on the jet stream, a figure that agrees with Allied observations. Thus, some 600 are still unaccounted for in North America, still potentially deadly. (U.S. Army drawing)

After that point, the main acknowledgements of these attacks were discrete posters warning folks what they looked like, and not to mess with them. Officials released limited information about balloon bombs on May 22, 1945, and on June 1 lifted the blackout on the explosion’s cause. Because the Japanese did not believe Americans could keep a secret, the program had been discontinued a couple months earlier as ineffective.

The Office of Censorship had for the most part been successful in a news blackout, although there had been hundreds found, plus many shot down by U.S. and Canadian fighters.

The posters remained up for years after the war, as some 9,300 balloon bombs had been launched, and only 300 still have been accounted for. Some have been found as recently as 1978. There is no doubt that hundreds are still out there, and still potentially deadly, as well: it has been projected by both the Japanese and U.S. authorities that some 10% made landfall in North America, leaving some 600 still unfound. They carried a varying mixture of high-explosive and incendiary loads.

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