WWII Files: Japan’s Secret Weapon- Exploding Balloons


WWII saw the development of some zany designs for weapons, such as when the U.S. developed pigeon guided missiles and (literal) bat bombs (the latter of which were a little too effective, accidentally destroying the testing base when they escaped), or when the Soviets trained exploding anti-tank dogs. Not to be left out of the fun, the Japanese developed their own oddball weapon. Starting in November of 1944, Japan launched over 9,000 devices they called “Fu-Gos” aimed at the United States and Canada. Fu-Gos were hydrogen balloons equipped with incendiary devices that, in theory, would be transported over the Pacific Ocean via the jet stream to devastate the landscape, perhaps starting massive fires in farm fields and forests across North America.

Fu-Gos, called fire balloons in the U.S., were approximately 70 feet tall, 30 feet in diameter and, fully inflated, held about 19,000 cubic feet of hydrogen. Launched from the Japanese island of Honshu, they were ultimately found in many states including Alaska, Washington, Oregon, California, Arizona, Idaho, Montana, Utah, Wyoming, Colorado, Texas, Kansas, Nebraska, South Dakota, North Dakota, Michigan and Iowa. Some were also found in Canada and a few turned up in Mexico.

Through experimentation, Japanese researchers found that at just over 30,000 feet altitude, the jet-stream could carry a large balloon about 5,000 miles across the Pacific in three days in late autumn when the stream was strongest.

They then developed an extremely clever, and simple, mechanical device to automate the flight of the balloons and release the explosives. To prevent too much fluctuation in altitude as the temperature changed in the night vs. the day, engineers created a system controlled by barometric sensors.  If the altitude got too low, below 30,000 ft, a small charge would fire, ejecting two sandbags mounted on a spoked wheel containing other sandbags and the explosive devices themselves. When the temperature heated up in the day time and the balloon rose above 38,000 feet, barometric-controlled valves would automatically open, releasing hydrogen and thus lowering the balloon to the desired level.

The control system was set up to last just three days at which point (in theory) there would be no sandbags left, just the incendiary devices ready to be released once the balloon dipped below 30,000 ft. At this point, the balloon would theoretically be over the U.S. and incendiary devices ranging from 5 kg to 15 kg would be released.  A fuse would also be lit which would burn for approximately 84 minutes before  igniting the balloon itself with its 19,000 or so cubic feet of hydrogen then exploding.

The balloons were made of “washi,” a tough paper made of mulberry bushes. It was only available in limited sizes about the size of a map; so it was glued together with paste, often by teenage girls.

By the early months of 1945, the American people were starting to notice that something strange was happening. Balloons and explosions had been seen in many states and seven balloons were handed over to the military by bewildered citizens. U.S. fighter planes tried to intercept the balloons but they were only able to destroy about twenty, as the balloons typically flew at very high altitude and were amazingly fast and difficult to track down once a report of one came in.

In the end, these clever devices didn’t exactly have the intended effect. Of the 9,000+ launched, Japanese military officials estimated about 10% of them would reach America. Approximately 342 of the balloons were found or seen in North America, and the result was just six people killed, along with minimal property damage.

That said, had the balloons been launched in the summer, rather than late autumn and winter, they may have started significant fires as had been originally planned.  Further, one incident involving a fire balloon could have had major implications on the war. The balloon descended on the Hanford Nuclear Reservation in Washington state, landing on power lines and cutting power to the nuclear reactor cooling pumps. Fortunately, backup generators restored power before there was any damage or a nuclear meltdown.

As for how the Japanese had managed to get the balloons into North America, this was at first something of a mystery. Most military officials didn’t believe they had come all the way from Japan. Many thought Japanese soldiers were coming ashore on North American beaches and launching the balloons. The mystery was solved when scientists with the Military Geology Unit analyzed the sand from some of the recovered sandbags, examining its microscopic sea-life and mineral composition, and determined the exact beach it had come from, which indeed was not in North America, but in Japan.

Despite the ineffectiveness of the balloons, authorities were still concerned. Their ability to start fires couldn’t be denied and there was also the potential psychological effect they could have on the American people. More importantly, they knew the Japanese had been working to develop biological weapons and a balloon carrying such payloads could potentially do major damage.

To help get around the potential panic, people who found the balloons and reported it to the authorities were sworn to secrecy. In 1945 though, Newsweek ran an article on the weapons, and a similar story appeared in another periodical the next day. The U.S. Office of Censorship (yep, that existed for about four years) sent a notice to the media, asking them not to mention the balloons or  balloon-bomb incidents.

Exercising their rights, the press of course continued to notify the U.S. public of the dangers of approaching such balloons if encountered… or rather in reality they complied with the U.S. Office of Censorship and no further reporting was done on the balloons at this time.

This likely contributed to the single successful balloon attack of the war. A pregnant woman, Elsie Mitchell, her husband Pastor Archie of the Bly Christian and Missionary Alliance Church, and five Sunday school children were out for a picnic. While Archie was discussing good fishing spots with a couple construction workers who were working on the road where the group had stopped, Elsie and the kids went to search out a good spot for their picnic.  In the process, they found one of the balloons.

Not knowing anything about it, the kids and Elsie went to investigate, with the last words Archie ever heard his wife say, according to the Oregon newspaper, The Mail Tribune, being “Look what I found, dear!”

Richard Barnhouse, one of the construction workers, reported to the Tribune what happened next: “There was a terrible explosion. Twigs flew through the air, pine needles began to fall, dead branches and dust, and dead logs went up.”

When the construction workers and Archie rushed over, they found Elsie and the children’s bodies on the ground around a gaping hole in the earth.  Their clothes were on fire, which was quickly put out. All of them but one of the young girls, Joan Patzke, died instantly from the blast.  Joan lived for a few minutes after, but then passed away.

After these deaths, the U.S. Office of Censorship rescinded their former blackout on mention of the balloons and the public was informed of them and told if they found any to keep their distance and contact the authorities.

After six months of launches, the balloon attacks stopped abruptly in April of 1945. Allied forces had blown up two Japanese hydrogen plants, cutting resources needed for the balloons. In addition, Japanese commanders, seeing the balloon attacks weren’t very effective relative to the resources expended, discontinued the program.

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Bonus Facts:

  • There may have been a few more deaths thanks to these balloons had it not been for some park rangers.  In Hayfork, California one of the balloons landed in a tree and a crowd gathered under it initially, but were then kept back by the rangers.  The balloon eventually exploded, but no one was hurt.  The explosion, however, had just been the hydrogen.  The mechanism for deploying the bombs, and the bombs themselves, were still intact allowing military officials to study how the clever system worked.
  • Much less cleverly designed balloons, though with similar purpose, were used by the British to attack the Germans during WWII.
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