Written by Todd DePastino

The large Chinese surveillance balloon first spotted last week above Montana and then shot down by military aircraft off the Carolina coast brings to mind the last time balloons menaced the United States. During World War II, Japan tried to set North America ablaze by launching 9,000 fire balloons into the jet stream across the Pacific.

It’s a footnote in the history of World War II. But, at the time, what the Japanese called Fu-Go or the incendiary balloon bomb, was a major initiative designed to terrorize the United States.

The Japanese had gotten the idea from the British, who’d used incendiary balloons against Germany. The American West had suffered record droughts during the 1930s and early 1940s. Its vast forests, the Japanese reasoned, were tinderboxes just waiting to be lighted.

But Los Angeles is ten times the mileage from Tokyo than Berlin is from London. The Japanese had to engineer their fire balloons for long-distance travel. Never in the history of warfare had an attack been launched from a continent away.

Getting the balloons to fly 5,000 miles across the Pacific to the United States, however, was surprisingly easy.

That’s because of the “jet stream,” a narrow, fast-rushing band of wind shooting West to East across the ocean in the upper atmosphere. Americans knew little about the jet stream at the time, but Japanese physicists understood that if they could get a balloon up to 30,000 feet, the jet stream would carry it to the US Pacific coast in three days or less.

After much research and experimentation, the Imperial Japanese Army gave a greenlight to the project but didn’t allocate scarce rubber for the balloons. So, engineers substituted washi—the famous Japanese origami paper—glued together with potato paste. Thousands of school girls around the country were tasked with layering the squares of paper and assembling them into big sheets.

The glue was edible. In war-ravaged Japan, the availability of potato paste was a production problem. The Japanese had to allow for significant loss of it on the job.

By fall of 1944, the army had gathered enough glued washi to make 9,300 balloons, each over 30-feet in diameter. Filled with hydrogen and attached to a carriage hanging from ropes, each balloon could deliver a couple hundred pounds of ordnance to American shores.

It was one thing to launch a balloon into jet stream. It was quite another to keep it there. Here’s where the Japanese showed true engineering genius.

During the heat of the day, the hydrogen trapped in the balloon would expand, raising the floating incendiary above the jet stream. Engineers added a release valve, which opened whenever the balloon’s internal pressure rose above the point needed to keep it in the jet stream’s narrow band.

The cold of night presented the opposite problem. The hydrogen would condense, lowering the balloon below the jet stream. To compensate, designers fixed a horizontal aluminum wheel beneath the carriage. Around the wheel hung 32 bags of sand. Above each sand bag was a trigger connected to a barometer set to release the bag at timed intervals as the barometric pressure dropped. As the sand bags fell, the balloon rose back into the jet stream.

By the time the balloon had lost its hydrogen and its sand bags, it would be over the North American land mass and deliver its deadly cargo to the ground.

The first reports of mysterious explosions in the Mountain West and odd balloons found floating off the California coast came the first week of November, 1944. Navy pilots tried to shoot the fast-moving incendiaries down over Alaska. A few balloons landed in populated areas, but the vast majority disappeared into the wilderness.

As word of balloon discoveries spread, the United States Army tried to contain the crisis. It asked the media not to report on the fire balloons so as not to panic the public or alert the Japanese to the success of their experiment.

A few smalltown newspapers and radio stations did warn residents to stay away from any shiny metal objects or origami paper they came across. But, for the most part, news outlets abided the Army’s request, and most Americans never knew of the 9,000 enemy balloons sent their way.

In the meantime, Military Intelligence struggled to figure out where the balloons came from and what they were designed to do. Ignorant of the jet stream, government meteorologists guessed that these attacks had to have originated within the US. Perhaps disloyal Japanese Americans incarcerated at internment camps throughout the Mountain West had secretly devised the weapons.

Others thought the balloons might have been launched from Japanese submarines off the coast.

Few suspected that these were, in fact, history’s first intercontinental weapon attacks.

An Army colonel investigating the matter took some sandbag samples to the United States Geological Survey’s Military Geology Unit. A team of mineralogists put the sand under the microscope and did some of the most clever forensic geological work in history.

Based on the unique mineral composition of the sand, lacking all coral and granite, and heavy on volcanic rock, scientists determined that the sand could only have come from Honshu, the largest island of Japan. US investigators were stunned by the finding.

Meanwhile, in Japan, military leaders scanned American media to determine the success of their experiment. They saw no reports of fire or destruction rained down on the US from the sky. The Japanese figured Fu-Go had been a failure.

The truth was, it had succeeded almost as planned. Of the 9,300 balloons launched at the United States, at least 300 had landed in North America. But the rains had returned to the West, and wet ground and snowpack meant that no serious fires broke out.

A map of fire balloon discoveries shows one landing as far east as Detroit. For years after the war, people discovered remnants of fire balloons throughout the Great Plans. In 1947, two farmers in Nebraska ran across great sheets of washi and used them as hay tarps. The last fire balloon was discovered in 2014. But more are undoubtedly still out there, waiting to be stumbled upon. If you do see one, don’t touch it. It might be configured to explode when moved.

That’s what happened on May 5, 1945, at a remote mountain location eight miles east of Bly, Oregon. Reverend Archie Mitchell and his pregnant wife Elsie had a group of five Sunday School students with them for a picnic. Driving up Gearhart Mountain, they found their preferred spot blocked off, so they continued down the road to Leonard Creek.

Archie stopped the car, and the eager children jumped out, followed by Elsie. While unloading the picnic baskets, he heard one child exclaim, “Look what I found!”

Elise and the other kids went over to check out the discovery. Moments later, there was an explosion.

Elise Mitchell and the five children with her were the only Americans killed by enemy action on the US continent during World War II.

On the monument are listed the names and ages of each victim:

Edward Engen, age 13
Jay Gifford, age 13
Elsie Mitchell, age 26
Dick Patzke,age  14
Joan Patzke, age 13
Sherman Shoemaker, age 11

A sad epilogue to the story: after the war, Archie remarried and moved to Da Lat, Vietnam, where he served as a missionary. In 1962, a team of Viet Cong guerillas burst into Archie’s home and took him captive. He was never seen again.