As US planes bombed Japan during WWII, the Japanese sent balloons across the ocean to set the US on fire

  • As the US went on the offensive in the Pacific during World War II, the Japanese looked for ways to strike back at the US mainland.
  • The Japanese had limited resources, so they turned to a low-tech method to launch long-range attacks: balloons loaded with bombs.
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On May 5, 1945, Rev. Archie Mitchell, his pregnant wife Elsie, and five children from Mitchell's congregation were heading for a picnic at Gearhart Mountain near Bly, Oregon.

As Archie went to find a parking spot, the children came across a strange metal contraption attached to a large balloon. Suddenly, the contraption exploded, killing all five children and Elsie.

They were the first and only victims of a Japanese Fu-Go balloon bomb, and the only Americans killed by enemy action in the continental US during the war.

Launched from Japan, the bomb was one of 9,300 similar balloons intended to wreak havoc on the mainland US by starting massive forest fires and terrorizing the public.

The only way to strike back

Using balloons to carry bombs was not a new idea. From 1942 to 1944, the British had sent almost 100,000 balloon bombs against Germany as a cheap way to increase the cost of the war for the Nazis. (Their balloons were effective, but the British dropped the effort as the air war turned in their favor.)

Japan experimented with balloon bombs as early as 1933, but they were not seriously considered until after the Doolittle Raid on April 18, 1942. That raid, in which US bombers took off from aircraft carriers and attacked Tokyo and other cities, made striking back at the US mainland a priority for the Japanese.

Japan's ability to strike the US mainland was severely limited. It had no airstrips close enough to launch bombers — even for a one-way trip — and it couldn't spare the ships and aircraft needed for another Pearl Harbor-style attack.

But Japan was committed. It had used submarines to bombard and launch airstrikes on the US mainland, but those attacks resulted in very little damage.

They decided to revive the semi-abandoned balloon-bomb project. By 1943, 200 balloon bombs were created in a joint army-navy plan to launch them from submarines roughly 600 miles from the US coast. But before the plan could be executed, the submarines were recalled for operations around Guadalcanal.

The need to strike back became only more urgent when American B-29s began bombing Japanese cities in 1944. So Japanese engineers created a longer-range balloon.

A complex weapon with a simple mission

Fu-Go balloons were made of paper called washi, which came from the bark of a kozo tree. They measured about 33 feet in diameter and were filled with 19,000 cubic feet of hydrogen.

The balloons had a system to maintain altitude as they floated toward North America.

If the balloon rose above 38,000 feet or if pressure reached a critical level, a discharge valve would automatically vent the gas. Each balloon also carried 32 sandbags, and when it fell below 30,000 feet, an electrical system would drop two sandbags at a time, causing it ascend again.

Once all the sandbags were dropped — which usually took three to four days, depending on windspeed — the balloon would release its ordnance and self-destruct.

Fu-Go balloons typically carried either one 33-pound high-explosive bomb or one 26-pound incendiary device with explosive charges. They were released from three launch sites on Honshu, Japan's biggest island, and traveled along the jet stream across the Pacific Ocean.

Some balloons were equipped with radios that broadcast a signal, allowing the Japanese to track their progress. In total, the Japanese launched 9,300 balloons between November 1944 and April 1945.

Massive potential but minimal effect

The Allies first encountered the balloons on November 3, two days after the first launch, when a ship recovered the remains of one floating in the ocean. There was initially more confusion than concern.

But four weeks later, reports of dozens of armed balloons being discovered along the West Coast started making American leaders nervous.

The US military initially kept the balloons a secret. There was concern that if the public knew about potentially thousands of balloons loaded with bombs falling randomly along the West Coast it could generate the mass panic that the Japanese wanted. There was also a fear that they could be carrying biological or chemical weapons.

The Office of Censorship asked all media outlets give the balloon incidents no publicity whatsoever. The outlets complied.

Allied planes in Asia and North America were sent to intercept the balloons wherever and whenever they were found. Once it became clear the balloons were filled with hydrogen, US bombers destroyed most of Japan's hydrogen plants.

The bombs were largely ineffective. Only about 900 are estimated to have actually reached North America, and they were too scattered to do much damage.

Three hundred landed in the US, with some going as far as Alaska, Michigan, and Texas. Dozens more landed in Canada and Mexico.

A strange legacy

Apart from six deaths, the only real damage they caused were two small brush fires and the momentary loss of power to the Hanford Site in Washington state, which, coincidentally, was producing plutonium for the Manhattan Project.

After the deaths of Mitchell and the children, the military broke its silence on the balloons. But the silence had been useful. By that time, the Japanese had cancelled the operation, concluding it had failed since there were virtually no reports of fires or chaos.

Fu-Go balloons continue to be discovered. The Royal Canadian Navy disposed of one in 2014, and the remnants of another were found just last year in British Columbia.

The balloons' mission was one of the longest-range attacks ever conducted. Since it traveled over 5,000 miles, the Fu-Go balloon is the first weapon system ever to have intercontinental range.

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