Fu-Go - The Balloon Bombs of Japan

One of the most remarkable weapons of the Second World War was the so-called Japanese balloon bomb or “Fu Go” that was an early example of using the winds in the upper atmosphere to conduct a military attack.

During the latter stages of the war, people in various parts of the USA became aware of sudden explosions that appeared to be taking place in random fashion across the country. Little damage was done but the US Military, particularly the Air Force, became increasingly interested.

After investigating the site of one such explosion they made an astonishing discovery. It appeared as though the explosions had been caused by bombs carried by some type of lighter than air balloon - and a very large one at that. It was calculated that the balloon in question was, when inflated, about 10m (33 ft) in diameter.

Above: A captured Fu-Go balloon relaunched by the American Military for research purposes. (Image from Wikipedia Commons - click to enlarge)

By examining the sand ballast attached to the object they were able to establish that the sand came from Japan and that the balloon was filled with hydrogen. Furthermore it was found that the balloon itself was made from a special type of paper called washi – a Japanese product.

It was realised that the Japanese were launching bomb-carrying balloons from Japan, and these were climbing to an altitude of around 10km where they were picked up by the upper level jet stream that carried them across the Pacific Ocean to the United States. After a journey of around three days the balloons arrived over North America and the bombs, usually consisting of incendiary and antipersonnel devices, were jettisoned automatically.


Left: The Fu-Gos were carried across the Pacific Ocean from Japan to North America in the upper air jet streams. A typical journey took three days. (Click to enlarge)

Jet streams are high speed rivers of air moving from west to east in the upper levels of the atmosphere and occur as a result of temperature differences and the spin of the Earth. Wind speeds in excess of 250 kph (155 mph) sometimes occur.
The jet stream made visible by cloud. This view taken from the Space Shuttle, shows the jet stream across eastern Canada in May 1991. (NASA image - click to enlarge)

Normally there are four such streams, two in each hemisphere, called the polar jet and subtropical jet and these tend to move in waves around the Earth. These jets also move north and south according to the seasons and affect different parts of the USA at different times of the year.

The US Government wanted to avoid public panic and ordered that the presence of the balloons be kept secret, but after a family was killed by an explosion in Southern Oregon, warnings were issued to the public.

Between November 1944 and April 1945 the Japanese launched some 9300 balloons with around 300 reaching the USA. Bombs were dropped over widespread areas including Alaska, Washington, Oregon, California, Arizona, Idaho, Montana, Utah, Wyoming, Colorado, Texas, Kansas, Nebraska, North and South Dakota, Michigan and Iowa, as well as Mexico and Canada. Interestingly there were a few cases where the balloons missed their mark and circumnavigated the globe, crossing back over Japan after a week or so in the air.

Government authorities were particularly worried that the incendiary bombs could trigger forest fires and even more by the possibility that the balloons could be used to introduce biological agents and livestock diseases into the USA. Fighters were ordered to intercept and shoot down the balloons wherever possible but after B29 bomber raids destroyed two of Japan’s main hydrogen producing plants in April of 1945, the Japanese abandoned the offensive.

Left: Gun camera footage of Fu-Go's being shot down by American fighters during the latter stages of World War 2. (Image from Wikipedia Commons)

The Fu Go balloon bomb would go down in the history books as a fairly ineffective device but it produced widespread concern across the USA and was one of the very few times the mainland of North America was actually attacked by an enemy during armed conflict.