The Deadly Japanese Weather Balloons Of World War II

“An awful lot of this was just ‘put them up there and see what happens.” —Dave Tewksbury, geoscientist discussing Japan’s balloon bombs

In A Nutshell

Although it’s sometimes said there were no enemy-inflicted deaths on the US mainland during World War II, that’s not actually true. In fact, six civilians were killed in Oregon by a bomb that infiltrated the States by hitching a ride on a beefed-up weather balloon. This “balloon bomb” was one of about 9,000 that were launched from Japan with the intentions of floating across the Pacific and wreaking havoc on the US.

The photo above is from a US Navy training film documenting the balloons. This photo shows the ballast system.

The Whole Bushel

During World War II, the United States’ geographical position on the globe made it rather difficult for the Axis powers to mount a direct assault. It was much easier in, for example, border-sharing European countries. Still, attack efforts were made, and some of those strikes were surprisingly farfetched—most notably, when the Japanese attached bombs to balloons and launched them from across the ocean toward North America. What’s even more surprising than the Japanese thinking this plan might work was that it actually did work—at least to an extent.

The plan came about in 1944 after Japanese researchers realized that during the winter there was a strong air current that traveled from Japan to the west coast of the United States. This gave them the idea to create what essentially became the first intercontinental weapon system, which depended entirely upon hydrogen-filled balloons.

The balloons were around 10 meters (33 ft) in diameter and were made of rubberized paper or silk. Dangling from each one was a bomb carrying up to 15 kilograms (33 lb) of incendiaries. Built into the balloons were barometer-controlled valves, which released hydrogen if the balloon floated too high. Additionally, attached sandbags were dropped if the balloon drifted too low during its 30–60 hours of flight time. Out of the approximately 9,000 balloon bombs released, it’s estimated only 342 landed in the US.

For the most part, the balloons that did make it to the US were largely unsuccessful. A few of them caused minor damage but no injuries, and, ironically, one hit a nuclear weapons plant in Hanford, Washington but only caused a temporary blackout. While some civilians noticed the flying objects, most stayed unaware, as the US government urged the newspapers and radio stations to not report on the balloons. This lack of media coverage led the Japanese to assume their “fire-balloons” weren’t working as planned. In addition, their hydrogen supplies were dwindling, so in early 1945 they decided to scrap the whole balloon campaign.

Although keeping the public unaware of the floating bombs might have helped to deter the Japanese from continuing with the plan, it also left citizens vulnerable. Consequently, on May 5, 1945 in Oregon, a pregnant Sunday school teacher and her five teenage students were killed as they investigated a curious balloon that they spotted while heading to an afternoon picnic. Obviously, when they picked up the item, they had no idea it was a deadly device sent from an enemy nation. Those six victims were the only enemy-inflicted casualties on the US mainland in all of World War II.

Naturally, many of the bombs are unaccounted for, and may possibly still pose a safety risk. As recent as 2014, a half-buried balloon bomb was discovered by two forestry workers in British Columbia. Not knowing if the device was live or inert, a bomb disposal team safely exploded the weapon with C4. Today, there’s no telling how many more fire balloons remain undiscovered throughout western North America.

Show Me The Proof

Featured photo credit: US Navy via National Geographic
National Geographic: Japan’s Secret WWII Weapon: Balloon Bombs
Wired: May 5, 1945: Japanese Balloon Bomb Kills 6 in Oregon
The Canadian Press: Military unit blows WWII-era Japanese balloon bomb to ‘smithereens’