80 Years Of Operation Fu-Go: When Japan Transformed Balloons Into ‘ICBMs’ To Turn U.S. Into An ‘Inferno’ 

When Japan first launched balloon bombs at the United States during World War II, they technically became the world’s first intercontinental ballistic missiles. Though balloons may not have proved to be effective weapons, they were a product of wartime scientific innovation. 

Recently, a unique “balloon war” has unfolded between North and South Korea. North Korea has launched over 1,000 balloons filled with trash and manure into South Korea, retaliating against South Korean civilian campaigns of sending propaganda leaflets across the heavily fortified border.

These exchanges have further escalated tensions between the two nations amid a diplomatic stalemate over North Korea’s nuclear program.

The use of balloons in conflict isn’t new. During World War II, Japan became the first country to weaponize balloons on a large scale. While their efforts weren’t wholly successful, they left a mark in the annals of unconventional warfare. November 2024 marked 80 years since Japan’s launch of balloon bombs toward the US mainland—a campaign dubbed Operation Fu-Go.

Operation Fu-Go: Japan’s Balloon Bombs

Between November 1944 and the spring of 1945, Japan launched fusen bakudan (balloon bombs) into the Pacific jet stream, aiming to strike North America. Developed at the Imperial Japanese Army’s Noborito Laboratory, these hydrogen-filled balloons carried incendiary and explosive payloads designed to ignite forest fires in the US Northwest and Canada, thereby diverting American resources from the Pacific theater.

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Of the approximately 9,000 balloons launched, only about 1000 reached North America, and none achieved the intended large-scale devastation. However, the operation showcased Japan’s innovative approach to psychological and resource warfare, even as its practical impact remained limited.

The Genesis Of An Unconventional Weapon

The idea of balloon bombs emerged as early as 1933 as part of Japan’s “Proposed Airborne Carrier” research. The concept gained traction after the 1942 Doolittle Raid exposed Japan’s vulnerability to American air attacks.

The Noborito Research Institute, tasked with developing secret warfare technologies, revived the idea as a way to retaliate against the US. The Noborito lab was responsible for “secret warfare,” including poison research and counterfeit money production.

Initially, there were plans to launch balloons from Japanese submarines along the US West Coast. However, this research was abruptly halted when the submarines were redirected to the Guadalcanal operation in August 1943.

In late 1943 and early 1944, meteorologists, supported by engineers working on the balloon project, tested the winter jet stream. They found that a balloon could travel for about 60 hours on this jet stream, potentially reaching the US. This breakthrough led to the production of 10,000 balloons for launch in the winter of 1944-45.

Due to wartime shortages, only 300 balloons were made from rubberized silk; the rest used washi paper crafted from the bark of the kozo tree.  Schoolgirls were conscripted to help manufacture the balloons, working in seven factories around Tokyo, but were kept unaware of the balloons’ purpose.

Execution And Challenges

When inflated with hydrogen, the balloons expanded to 33 feet in diameter. Each was equipped with a payload of five bombs, including a 33-pound anti-personnel device and incendiaries.

The first balloon bomb, named Fu-Go (meaning “wind-ship weapon”) was launched on November 3, 1944, to honor Emperor Meiji’s birthday. Despite logistical challenges, Japan pressed on with the campaign, highlighting its resourcefulness even as the war tilted against it.

However, launching was not without its challenges: each balloon took between 30 minutes and an hour to prepare, and it could only be launched under specific wind conditions. Between November and March, there were only about 50 favorable days for launching, with a maximum of 200 balloons launched per day.

While Fu-Go failed to achieve significant strategic results, it marked an early attempt at intercontinental warfare and showcased the lengths nations would go to innovate during the conflict.

Balloons Became Weapons

The Japanese balloon bomb campaign remained a closely guarded secret for much of the war.

Just two days after the first launch, the US Navy patrol off the coast of California recovered cloth debris with Japanese markings. It wasn’t until weeks later that the military realized the significance of these balloon sightings. Reports of balloon debris and unexplained explosions began to surface across the western US.

Initially, the US military was alarmed but uncertain about the balloons’ purpose. Concerns ranged from incendiary attacks to the possibility of biological weapons. According to the National Museum of the US Air Force, Japan launched approximately 9,000 balloons over five months, carried by high-altitude winds more than 6,000 miles across the Pacific. Of these, about 1,000 reached North America, with 285 documented incidents, mainly in the northwest, though a few reached as far as Michigan.

To prevent public panic and deny Japan intelligence on the campaign’s effectiveness, the US government, in cooperation with the media, adopted a policy of silence. On January 4, 1945, the Office of Censorship requested that media outlets refrain from discussing the balloons. This silence worked: Japan only learned of one balloon incident through the Chinese newspaper Takungpao.

However, on May 5, 1945, a balloon bomb exploded in Oregon, killing six picnickers, including children and a pregnant woman. These were the only civilian casualties caused directly by enemy action on US soil during World War II. This tragedy forced the military to break its silence and issue public warnings to avoid tampering with unexploded devices.

The End Of The Balloon Campaign

Despite continuing balloon sightings, the frequency of launches sharply declined by April 1945, and by late May, no further balloon flights were reported. Disheartened by the campaign’s limited success, the Japanese halted their balloon attacks in April 1945.

In September 1945, a team of American scientists arrived in Japan to assess its wartime scientific efforts. Their findings revealed that Japan had intended to launch 20,000 balloons but had fallen short due to resource shortages.

There was a significant depletion of kozo trees, which were vital for paper production, and the US bombing of Japan’s chemical plants severely disrupted hydrogen supplies. Another major factor was the lack of concrete evidence that the balloons had reached their target or inflicted serious damage.

The Museum: Preserving A Dark Chapter Of History

Today, the story of Operation Fu-Go is preserved at the Defunct Imperial Japanese Army Noborito Laboratory Museum for Education in Peace.

Located at Meiji University’s Ikuta campus, the museum delves into the history and mechanics of balloon bombs, which were once regarded as “decisive weapons.” It provides a comprehensive overview of Operation Fu-Go. It reveals chilling details about initial plans to arm the balloons with biological weapons, including germ agents targeting humans and the rinderpest virus, a devastating livestock disease.

Through its exhibits, the museum seeks to educate visitors about the perils of secret warfare, underscoring the ethical consequences of such tactics and promoting a message of peace.

While the balloon bomb campaign failed as a military strategy, it represents a fascinating chapter in technological warfare. These balloons were, in essence, the world’s first intercontinental weapons, pushing the boundaries of what was considered possible in military technology.