The Secret History of Japan’s Balloon Bombs

Towards the end of the Second World War, Japan launched thousands of bombs at the North American mainland, resulting in the war’s only deaths that occurred in the contiguous United States. Why have we never heard of this?

Japan’s Wind Weapons

In 1944–45, the Japanese Fu-Go project released at least 9,300 firebombs aimed at US and Canadian forests and cities. The incendiaries were carried over the Pacific Ocean by silent balloons via the jet stream. Only 300 examples have ever been found and only 1 bomb resulted in casualties, when a pregnant woman and 5 children were killed in an explosion upon discovering the device in a forest near Bly, Oregon.

Japan’s balloon bombs have been found over a wide range of territory, from Hawaii and Alaska to central Canada and throughout the western United States, as far east as Michigan and even over the Mexican border.

fu-go japan balloon bombs

Diagram of a balloon bomb

This excerpt from an article written by geologists at the Missouri University of Science and Technology explains how the Fu-Go bombs worked:

The balloons were crafted from mulberry paper, glued together with potato flour and filled with expansive hydrogen. They were 33 feet in diameter and could lift approximately 1,000 pounds, but the deadly portion of their cargo was a 33-lb anti-personnel fragmentation bomb, attached to a 64–foot long fuse that was intended to burn for 82 minutes before detonating. The Japanese programmed the balloons to release hydrogen if they ascended to over 38,000 feet and to drop pairs of sand filled ballast bags if the balloon dropped below 30,000 feet, using an onboard altimeter.

Military Geologists Unravel the Mystery of the Floating Bombs

At the time it was inconceivable that the balloon bomb devices could be coming from Japan. Ideas concerning their origins ranged from submarines landing on American beaches to Japanese-American internment camps.

However, upon analysis of the sandbags attached to the bombs, US military geologists concluded that the bombs had to originate in Japan. It was later discovered that the devices were constructed by young girls, after their schools were converted into makeshift Fu-Go factories.

japan's balloon bombs

An artists representation of Japanese school girls building the balloons that would carry the bombs to the US.

A US Media Blackout

Though the US government was aware of the balloon bombs, the Office of Censorship issued a press blackout on the subject. This was to both avoid panic among the American public and keep the Japanese unaware about the effectiveness of the bombs. Perhaps as a result, the Japanese only learned of one bomb that landed in Wyoming without exploding.

After the single deadly explosion in Oregon, the government lifted the media blackout on the bombs. However, if no blackout had ever been in place, those 6 deaths may have been avoided.

Perhaps unconvinced of its efficacy, Japan’s government cancelled the project after only 6 months.

The Legacy of the Balloon Bombs

Ingenious, diabolical and ultimately ineffective, the Fu-Go project was the world’s first intercontinental weapons delivery system. It was also a sort of last-ditch effort by a country with damaged military and limited resources. The balloon bombs were possibly viewed as a means of exacting some revenge for the extensive US bombing of Japanese cities, which were particularly vulnerable to incendiary attacks.

Throughout the years, Japan’s balloon bombs have continued to be discovered. One was found as recently as October 2014 in the mountains of British Colombia.

japan balloon bombs

A balloon bomb found in rural Missouri

Graham is an editor and contributor at Made From History. A London-based writer originally from Washington, DC, he holds a master's degree in Cultural History from Malmö University in Sweden. Graham also contributes environmental news articles to asiancorrespondent.com and latincorrespondent.com.