We’re all aware that the U.S. bombarded Japan with both conventional as well as atomic bombs in World War II. What isn’t as well known is that Japan also bombed the United States.

The Japanese created balloons that would carry bombs across the Pacific at high altitudes via the jet stream. The Japanese called the the balloons fusen bakudan meaning “fire balloon” and referred to the project as “Fugo” or “Fu-Go.” The goal of the program was to terrify Americans and possibly cause the western forests to catch fire.

The balloons were pretty big – over 30 feet in diameter – made of paper and filled with hydrogen gas. They could carry about 1,000 pounds of payload and were equipped with high explosives to cause damage as well as incendiary devices to cause fires. When launched, the balloons would ascend to around 35,000 feet and catch with Pacific Jet-Stream eastward.

The design of the balloons was ingenious. As they traveled, the hydrogen would leak out which would cause them to descend. At about 25,000 feet an altimeter would trigger the dropping of sandbags they carried to counteract the decreased gas. The Japanese calculated that by the time the balloons were over the American mainland they would be out of sandbags and the balloons to descend towards the ground. When the balloon had descended low enough a altimeter would trigger dropping of the bombs. When the last bomb was dropped a fuse would light and ignite the hydrogen in the balloon. (Note that not all these steps occurred flawlessly.)

They were launched beginning on November 3, 1944 until around May of 1945. During that six month period over 9,000 Fire Balloons were dispatched towards America.

Many of the balloons likely didn’t make it to North America, but hundreds (maybe thousands) did. Fire Balloons were found in areas from Northern Mexico to Canada and as far east as Texas, Iowa and Michigan.

Most of the balloons didn’t cause much damage – usually small fires – but there were two outliers:

• On May 5, 1945, six people (five of them children) near Bly, Oregon were killed by the payload of an exploding balloon – members of a Sunday School class having a picnic. A monument stands at that site today and announces it as “The “only place on the American continent where death resulted from enemy action during World War II”. 
• The second serious incident occurred when a balloon came down on power lines near Hanford Washington causing the power to be cut to a Manhattan Project site, shutting down work for three days and risking nuclear meltdown (fortunately, backup generators kicked in).

Balloons are still being found; most recently, one was found in British Columbia and disposed of in 2014. Here’s a short video from National Geographic about the Japanese balloon bomb program: