Fu-Go: Japan’s Paper Balloon Bombs and the Picnic in Bly, Oregon

On the morning of Saturday, May 5, 1945, a young minister named Archie Mitchell drove his pregnant wife, Elsie, and five children from his Sunday school class into the pine forest on Gearhart Mountain, about 13 miles northeast of the small town of Bly in southern Oregon. They planned to fish and picnic near Leonard Creek. While Archie parked the car and unloaded lunch, the others walked ahead and found something strange lying on the ground. Someone called out that it looked like a balloon. Archie shouted a warning, but it was too late. The blast killed all six of them.

They were the only people killed by enemy action on the mainland of the United States during World War II. The weapon that killed them had been launched from a beach in Japan, more than 5,000 miles away, and carried across the Pacific by a fast river of high-altitude wind that most Americans had never heard of. Its envelope was made of paper glued together with a paste made from a root vegetable, and much of it was assembled by teenage schoolgirls who were never told what they were building.

The Japanese army called the project Fu-Go. Over six months it sent about 9,300 of these balloons toward North America. Most vanished into the ocean. A few hundred reached land, from Alaska to Mexico and as far east as Michigan. How they were built, how they flew and how the United States kept them secret is one of the strangest chapters of the war.

Revenge for the Doolittle Raid

The idea was older than the war with the United States. In 1933 Lieutenant General Reikichi Tada started a balloon bomb program at the army’s Noborito research institute near Tokyo, later known as the Ninth Military Technical Research Institute. It went nowhere for years. Then, on April 18, 1942, sixteen American B-25 bombers led by James Doolittle struck Tokyo. The damage was small, but the shock was not. The Imperial General Headquarters ordered Noborito to find a way to hit back at the American mainland.

The first plan was to carry smaller balloons across the Pacific by submarine and launch them close to the West Coast. In September 1942 a submarine-launched floatplane did drop incendiaries on an Oregon forest, but the woods were damp and the fires fizzled. Soon every submarine was needed for the fighting around Guadalcanal, and the submarine plan was dropped. If balloons were going to reach America, they would have to fly the whole way from Japan.

A river of air, reported in Esperanto

That depended on wind. In the 1920s the Japanese meteorologist Wasaburo Oishi tracked about 1,300 small pilot balloons from the aerological observatory at Tateno, northeast of Tokyo. He found a powerful west-to-east current of air high above Japan, especially in winter. It was one of the first clear measurements of what we now call the jet stream.

Oishi was also a devoted Esperantist, the head of Japan’s Esperanto society, and he published his observatory reports in that invented international language. Few meteorologists outside Japan read them. When American B-29 crews reached Japan in late 1944, winds of up to 230 miles per hour at their cruising altitude took them completely by surprise.

For Fu-Go, the army turned to Hidetoshi Arakawa of the Central Meteorological Observatory, who drew on Oishi’s work. Arakawa calculated that a balloon riding the winter jet stream at around 30,000 feet could cross the Pacific in roughly two to four days. The strongest winds blew from November to March, so the balloons had to be ready by late autumn 1944.

Paper, paste and schoolgirls

With rubber and silk scarce, the engineers chose washi, a tough traditional paper made from the inner bark of the kozo, or paper mulberry, shrub. Thin sheets were laminated in four or five layers and glued with paste made from konnyaku, a starchy root also used in Japanese cooking. Each envelope needed about 600 pieces of paper and, when inflated with hydrogen, measured about 33 feet across.

The work was done by hand across Japan, much of it by girls from secondary schools who had been mobilized for war work. Large indoor spaces were needed to inflate and test the envelopes for leaks, so assembly moved into places such as theaters and the Ryogoku Kokugikan, the great sumo hall in Tokyo. The girls were told to keep their nails trimmed and to avoid hairpins, which could puncture the paper. They were not told that they were building weapons meant for America.

A machine that kept its own altitude

The hard engineering problem was altitude. In daylight the sun warmed the hydrogen and the balloon rose; at night the gas cooled and it sank. Left alone, a balloon would sink into the ocean long before reaching land. The Noborito team solved this with a clever automatic system hung beneath the envelope.

A relief valve vented hydrogen if the balloon climbed too high. If it sank too low, aneroid barometers triggered small charges that dropped sandbags from a cast aluminum ring. Each balloon carried 32 sandbags, released in pairs, so it bobbed across the ocean between roughly 30,000 and 38,000 feet for about three days. When the last sandbags were gone, the next drop released the bombs instead.

The standard load was four incendiary bombs of about 11 pounds and one 33-pound high-explosive anti-personnel bomb. The designers also added a self-destruct system. A fuse lit by the release of the last bomb was meant to set off a block of picric acid, destroying the mechanism, and then ignite the hydrogen in the envelope. It often failed, which is why many balloons were later found nearly intact.

Launching on the emperor’s birthday

The first balloons were released on November 3, 1944, a date chosen because it was the birthday of the Meiji emperor. Three army battalions operated launch sites on the Pacific coast of Honshu: at Otsu in Ibaraki prefecture, which had its own hydrogen plant, at Ichinomiya in Chiba, and at Nakoso in Fukushima. It took a crew of around 30 soldiers up to an hour to fill and release a single balloon, and only on days with the right surface winds.

Witnesses near the launch beaches later remembered the balloons rising into the sky like giant jellyfish. About 9,300 were sent off: 700 in November, 1,200 in December, 2,000 in January, 2,500 in February, 2,500 in March and 400 in April. The last was launched on April 20, 1945.

Debris on the water, fire in the forest

On November 4, 1944, a Navy patrol southwest of San Pedro, California, pulled tattered rubberized fabric with Japanese markings out of the sea. It came from an earlier, smaller design. Within weeks more reports came in. On November 14 a balloon was found off Kailua, Hawaii. On December 6 witnesses near Thermopolis, Wyoming, heard an explosion, and investigators later found a crater and bomb fragments. On December 11 a nearly complete paper balloon was found near Kalispell, Montana.

At first American officials had no idea where the balloons came from. Some suspected they were being launched from submarines offshore, or even from internment camps for Japanese Americans or German prisoners of war. Scientists also feared the balloons might carry germs to the farm country of the West, and agricultural officials were told to watch for new diseases in crops and livestock. A postwar investigation found no such plans.

By August 1945 the Army had recorded 285 balloon incidents. Counts that include later finds put the total at somewhere between 300 and 360 balloons or pieces of balloons found in North America. They turned up across the West and Alaska, but also in Kansas, Nebraska, Iowa, Texas and Michigan. One came down near Nixon, Nevada, where a crew had to cut down a tree to recover it.

The most consequential landing was a lucky one for Japan, though Japan never knew it. On March 10, 1945, a balloon drifted into power lines near Toppenish, Washington, and caused a short circuit that cut electricity to the Hanford Engineer Works, the Manhattan Project site producing plutonium for the atomic bomb. It took about three days to bring the reactors back to full power. The fuel made at Hanford ended up in the bomb dropped on Nagasaki five months later Hanford plutonium also went into the core behind the deadly accidents told in our story of the demon core.

Asking the press for silence

The balloons did very little physical damage. American officials worried more about panic, and about what Japan might learn. Press reports of landings could help Japanese planners fine-tune launches and claim success at home. On January 4, 1945, the federal Office of Censorship sent a confidential memo asking newspapers and radio stations not to mention the balloons at all.

A few stories had already slipped out, including the Kalispell find, but after the memo the American press stayed almost entirely quiet. The only American balloon landing that Japanese intelligence ever confirmed was Kalispell, which it learned about from a report in the Chinese newspaper Ta Kung Pao on December 18, 1944.

Japanese propaganda broadcasts claimed fires and casualties on the American mainland, but planners in Tokyo had no real evidence. With no reports of success, rising costs and shortages of both paper and hydrogen, the army ended the campaign in April 1945.

Geologists read the sand

Meanwhile, a team of scientists was trying to answer a question that the censorship could not: where exactly were the balloons coming from? The clue was the ballast. Many recovered balloons still carried sandbags, and in early 1945 the sand went to the Military Geology Unit of the United States Geological Survey in Washington, D.C.

The work fell to a small team that included the paleontologist Julia Gardner, an expert on fossil shells, along with the diatom specialists Kenneth and Katherine Lohman and the mineralogist Clarence Ross. They studied the tiny shells, diatoms and minerals in the sand, which pointed to a beach on the east coast of Honshu.

Their leading candidate was Shiogama, near Sendai, with a second, less likely candidate at Ichinomiya in Chiba. Only the second was right, and aerial photographs of Shiogama that May were misread as showing launch activity. Still, it was an impressive piece of forensic science, done with microscopes rather than spies. By then the launches had already stopped.

Smokejumpers in the western forests

The greatest fear in the West was fire. The balloons arrived in winter, when forests were wet, but no one knew whether some might linger into the dry summer. The Army, the Forest Service and other agencies set up a plan, known as the Firefly Project, to put out any fire the balloons might start.

Part of that plan fell to the 555th Parachute Infantry Battalion, the all-Black airborne unit nicknamed the Triple Nickles. Barred from combat overseas by the segregation of the era, its paratroopers were sent to Pendleton, Oregon, in May 1945 and trained as smokejumpers. Over the summer and fall they made dozens of fire missions across the Pacific Northwest, parachuting into steep, forested terrain. The unit’s only fatality came during a jump on August 6, 1945. Their service went largely unrecognized for decades.

No major fire was ever traced to a balloon. Of the thousands of balloons launched, only about 20 were shot down by American and Canadian fighter planes.

Saturday, May 5, 1945

Archie Mitchell was the pastor of a church in Bly, a small lumber town in Klamath County. His wife, Elsie, was 26 years old and five months pregnant. On that Saturday they took five children on an outing: Dick Patzke, 14, his sister Joan Patzke, 13, Jay Gifford, 13, Edward Engen, 13, and Sherman Shoemaker, 11.

Archie stayed with the car while the others went ahead toward the creek. He later described what happened next: "As I got out of the car to bring the lunch, the others were not far away and called to me they had found something that looked like a balloon. I heard of Japanese balloons so I shouted a warning not to touch it. But just then there was a big explosion. I ran up there, and they were all dead."

The balloon had probably lain in the woods for weeks, its anti-personnel bomb still attached. The explosion left a hole about a foot deep and three feet across, and fragments were found up to 400 feet away.

They were the only people killed by enemy action on the mainland of the United States during World War II.

Because of the blackout, the local paper could report only that six people had been killed "by an explosion of unannounced cause." The deaths forced the government’s hand: people could not avoid a danger they did not know about. On May 22 the War Department released a statement warning the public about the balloons, and on June 1 the cause of the Bly explosion was made public.

A monument and a thousand paper cranes

In 1950 the Weyerhaeuser lumber company, which owned the land, built a stone monument at the site. When it was dedicated on August 20, 1950, Oregon Governor Douglas McKay said the victims were casualties of war "just as surely as if they had been in uniform." The site, now in the Fremont-Winema National Forest and known as the Mitchell Monument, was listed on the National Register of Historic Places in 2003.

A ponderosa pine near the monument still bears scars from the bomb fragments. Visitors call it the shrapnel tree. In 2021 the huge Bootleg Fire raced through the surrounding forest, but the monument and the tree survived.

The story has a gentler ending than anyone could have expected in 1945. In the late 1980s Yuzuru John Takeshita, a University of Michigan professor who had been incarcerated as a Japanese American boy during the war, learned that a friend’s wife had worked on the balloons as a schoolgirl. He put former schoolgirls in touch with the families of Bly. The women folded 1,000 paper cranes, a traditional symbol of peace and healing, as an expression of their regret, and some later traveled to Bly to meet the families in person. On the 50th anniversary of the explosion, in 1995, six cherry trees were planted at the site.

Still out there

Japan destroyed most of its Fu-Go records at the end of the war; much of what we know comes from the Smithsonian curator Robert C. Mikesh, whose 1973 study is still the standard account. Most of the balloons fell into the ocean, but some surely came down in remote forests and mountains.

They are still turning up. In 2014 two forestry workers near Lumby, British Columbia, found a balloon carriage with a live bomb, and a Royal Canadian Navy disposal team destroyed it. In 2019 remains of another balloon were found near McBride, British Columbia. The advice from officials has not changed since 1945: if you find something strange in the woods, do not touch it, and call the authorities.

The Fu-Go balloons are often described as the first intercontinental weapons, launched across an ocean with no pilot and no guidance except the wind. They belong with other odd wartime experiments, such as the plan to steer missiles with trained birds in Project Pigeon, and with the older dream of riding the wind that ended badly for the Andree balloon expedition in 1897. Bly was not the only remote American place touched directly by Japan’s war; a very different encounter played out on a Hawaiian island in the Niihau incident of 1941.

For more places where science and history meet, explore our interactive History Globe, which maps the events we have covered across time.

Further reading