Balloon-bomb damage could have been worse

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By Finn J.D. John
August 21, 2016

EDITOR'S NOTE: This column is a rewriting and thorough re-researching of a short column first published in October 2008, which you’ll find here.

ON JULY 9, 1945, residents of northwest Oregon started seeing heavy smoke rising into the air over the Coast Range.

It wasn’t an unfamiliar sight. Twelve years earlier, in 1933, the granddaddy of all Oregon forest fires had broken out in the same general region, and by the time it was snuffed out by early fall rains it had turned 350,000 acres of prime virgin forest into a moonscape. Six years after that, it had happened again.

And now, like a six-year jinx coming on schedule to haunt the state, the forest was on fire again. It would happen again six years further on, in 1951.

A diagram of the clockwork mechanism used to release ballast and vent gas from the envelope to keep the balloon aloft for the 72 hours it would need to cross the Pacific Ocean, and drop the bombs once it arrived. (Image: Smithsonian Press)

But there was one particularly interesting thing about the 1945 burn: Nobody knew how it got started. Both the earlier burns had been started by logging operations; this one, though, had just flared up, and when it was all over and done it was traced back to an almost inaccessible spot near the Salmonberry River — nowhere near any roads or logging operations.

No one will ever know for sure. But the best explanation for the outbreak of the third Tillamook Burn, five months before the end of the Second World War, is by far the most dramatic one:

Enemy action, in reprisal for the Doolittle Raids on Tokyo three years earlier.


HISTORIAN ROBERT MIKESH makes a solid case that the Doolittle Raids, launched in 1942 by the Pendleton-based 17th Bomb Group, shortened the war considerably by putting the Japanese military command into an intolerable psychological position. The scant physical damage done by the handful of B-25s was nothing compared with the damage they did to Imperial Japan’s pride, and after the raid the military was almost desperate to recover its lost “face.” Among other things, this led to the Japanese steaming out in force to meet the American Navy at Midway — in a battle that looked a lot more even than it turned out to be, because of how much more punishment the U.S. could take.

The system of inflating the balloons in low to moderate wind, sketched out. (Image: Smithsonian Press)

It also led to a flood of innovation from the Japanese, brainstorming up ways to put some kind of hurt on the American homeland like the Yanks had done to them. One gambit, tried once in 1942 without much success, was the firebombing of the forest near Brookings by a submarine-launched seaplane.

But probably the most interesting innovation to be inspired by the Doolittle raid was the world’s first intercontinental weapon system — a system based on a modernization of a technology from the 1700s: Hydrogen-filled balloons. They became known as “fire balloons.”

The Japanese had discovered that the jet stream runs from Japan straight across the Pacific Ocean to North America all winter long at speeds of over 100 miles an hour. At speeds like that, they realized, a balloon launched from Japan would reach the U.S. in about three days. So they got busy figuring out how to take advantage of that.

There were serious engineering problems, though, involved with overnight balloon flights. The sun would warm the gas during the day, increasing the lift; and it would then cool off at night. If left to its own devices, a balloon would simply sink into the ocean after sunset.

To deal with this, the Japanese engineers rigged the balloons with an ingenious clockwork mechanism rigged to an altimeter. When the balloon dipped below 30,000 feet or so, the mechanism would release one or two bags of ballast, sending the balloon back up into the right altitude range again. When the morning came and the expanding gas threatened to raise the balloon out of the jet stream, the clockwork would open a gas valve, venting some of the helium gas to keep it at the proper height.

Each balloon was rigged with enough ballast to go through two day-night cycles. On the third day, engineers calculated it would be over the continent, and the clockwork bomb-control device would drop its payload of incendiary or antipersonnel bombs, after which the balloon itself would self-destruct.


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An artist’s rendering of what the balloon launching site looked like during a heavy launch day, in late 1944 or early 1945. The tanks to the left contain hydrogen gas (Image: Smithsonian Press)

THE JAPANESE FINALLY got these weapons worked out to their satisfaction in the fall of 1944. On the island of Honshu, nestled among protecting hills, a team of schoolgirls worked to build the balloons out of tough, light mulberry paper; they were rigged with the clockwork, ballast and bombs and launched into the sky, one by one, for all that winter. A total of roughly 9,000 of them rose into the sky over Japan and started out across the Pacific Ocean. It was the longest-ranged attack in military history, a record that would stand until 1982 when the British broke it during the Falkland Islands war.

A few days later, odd things started happening in the American and Canadian West. A father and son on a fishing trip one morning on a north-woods lake saw a balloon drift by and disappear over a nearby hill — and then a big explosion echoed through the woods. Two farmers working in a field were startled by another big explosion. A mother was tucking her child in for the night when the tyke’s bedroom was lit up by the flash of a big explosion near the window.

A diagram of a fully-inflated balloon in flight. (Image: Smithsonian Press)

In all these incidents, all that remained of whatever it had been were metal fragments, blast craters and sometimes bits of mulberry paper.

The U.S. war department was not slow to realize that the Japanese had developed a weapon that, while not a war-winner, could certainly dramatically increase the amount of pain they’d be able to inflict. Should the Japanese think to rig the balloons with biological weapons — weaponized anthrax strains, smallpox virus, that kind of thing — they could do tremendous damage. And worse, if they continued to launch them when fire season began in the Pacific Northwest ….

Now, the Yanks didn’t understand what the jet stream was or how it worked yet, so they didn’t know, as the Japanese did, that it was a wintertime thing. Come July or August, when the entire Pacific Northwest was a giant tinderbox, the balloons would no longer be flying. That was a problem that could have been easily solved with bombs rigged with very-long-running timers or even temperature sensors that would set them off when they hit 80 degrees or so; but apparently the Japanese didn't think of that.

Indeed, so far as is known, the Japanese did none of these things; they contented themselves with sending traditional bombs. Of the 9,000 they launched, about 300 were found, and it’s estimated that another 500 or 600 either blew up harmlessly without witnesses around or fell into the woods somewhere and are still out there. But the U.S. government did such a great job of hushing the whole thing up that the Japanese concluded that the whole program was a miserable failure, and there was no discussion of continuing the program after April 1945.

The overall launch operation (Image: Smithsonian Press)

It was in May of 1945 that the fire balloons actually drew blood, when a group of church picnickers in the southern-central Oregon town of Bly found one of the balloons; while they were gawking and prodding it, it exploded, killing five children and a pregnant woman.

And then there was that mysterious forest fire that broke out in July, which we know today as the third Tillamook Burn ….


HISTORIANS ALMOST UNIVERSALLY agree there was nothing the Japanese could have done to win that war. They had picked a fight with a country that by the end of the conflict was out-producing the entire rest of the world combined. Although there were some bad moments in 1942, the outcome of the conflict was inevitable, particularly after American aircraft design caught up with and surpassed the Japanese Zero (arguably the best all-around fighter plane in the world until about 1943).

But had the Japanese developed it a year earlier, and had they loaded it with anthrax spores and put the bombs on six-month time delay fuses before sending them over the sea, they would have dramatically changed the way the war is remembered in the United States. And they probably would have changed the very landscape of the American West for decades.

(Sources: Mikesh, Robert C. Japan’s World War II Balloon Bomb Attacks on North America. Washington: Smithsonian Press, 1973; Juillerat, Lee. “Balloon Bombs,” Oregon Encyclopedia,; Weeks, Linton. “Beware of Japanese Balloon Bombs,” NPR History Dept., )

TAGS: #EVENT: #war #explosion #fatal :: #MYSTERIES: #xTheories :: #aviation #unluckyBreak


Background photo is a hand-tinted image of a fish wheel on the Columbia River near Beacon Rock, published circa 1910 on a picture postcard.
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