Japan sent 9000 bomber-balloons across the Pacific to attack America

This edited article about the Second World War originally appeared in Look and Learn issue number 727 published on 20 December 1975.

An American poster encouraging scrap recycling in the war against Japan

The first bombs had fallen on Tokyo and the Japanese General Staff was worried. It was true that the war was going well. Manila, Singapore and Hong Kong had fallen, and the Japanese troops were on the advance everywhere, driving the British and American forces before them, thereby proving to the Allies that the race they had always despised and underrated was a formidable enemy that must henceforth be treated with respect. But this bombing of Tokyo was another matter. For the first time the enemy had struck a blow at Japan’s precious soil, a matter of deep concern for the General Staff, not so much because of the dead bodies and the ruins left in the wake of the American bombers, but rather because the raid had made them lose ‘face’. It was, moreover, something that would inevitably happen again, and each time it did, the American people would rejoice and draw great satisfaction from it. National pride therefore demanded that some appropriate reprisal should be found.

It took the Japanese two years to find an answer to the bombing raids, and what they finally did come up with was nothing more than a bomb-carrying balloon, 33 feet (10 metres) in diameter, designed to travel across the Pacific at an altitude of about 35,000 feet (approx. 10,606 metres). Unlike the German rockets that came later, it was not possible to exercise any control over these balloons which had to travel on the prevailing air currents that moved towards America, generally at a speed of 100 to 200 miles (320 km.) an hour.

The Japanese made their first mass balloon attack in the spring of 1944, when they set loose two hundred trial gas bags. Not one of them reached America.

The next attack was launched in the November of the same year, and this time one of them reached the shores of America, where it gently subsided into the waters, but not before it had been spotted by a naval patrol craft. Unfortunately, as one of the sailors pulled it aboard, he slashed off with a knife its heavy undercarriage, which rapidly sank, taking with it all the gadgets and explosives which would have supplied the American authorities with vital information. The gas-bag, however, did give up one clue. It carried Japanese markings which made it quite clear that it was a secret weapon of some sort. But what sort of weapon?

The answer the authorities were looking for was supplied two weeks later when another burnt out and almost totally destroyed gas-bag was found in Montana. There was little enough to go on from the scraps that had been salvaged, but there was enough for the technicians who were put to work on them to find out their basic principles. Each balloon carried thirty sandbags, each weighing six pounds, (2 kilos) which were released successively by a tripping device that was affected by a barometer which released the sandbags whenever the balloon dropped below 30,000 feet (9143 metres). Another automatic control opened a valve to let hydrogen escape whenever the gas-bag rose above its normal travelling height; by these means it was hoped that the balloon would be able to maintain its proper height until it reached its objective. There was also a built in device to explode the balloon when the bombs had gone off.

Although it rapidly became obvious that the danger from the explosive bombs the gas-bags carried constituted only a minor threat, the authorities were alarmed. If the balloon assault continued into the following summer, they could well constitute a major fire hazard if any one of them landed in one of the many vast forests, which would go up like tinder. There was also the possibility that the Japanese might use the gas balloons to shower all sorts of germs down on the country.

The U.S. Government went into action. After asking for and receiving a voluntary censorship from the press and radio, veterinary surgeons and agriculture specialists were enlisted and farmers and ranchers in those areas where the balloons were likely to fall, were ordered to report the appearance of any strange disease among their livestock. In addition, decontamination chemicals were stored at various strategic points. In the forest areas of the West Coast a number of paratroop fire fighting units were created which would co-operate with the normal ranger service if any emergency arose.

It was learned after the war that the Japanese sent nine thousand balloons over the Pacific, but only between nine hundred and a thousand of them reached the American continent. But owing to the precautions that had been taken, very little damage was done. A few small fires were started which were quickly put under control, and there was a sad incident when a group of children on a picnic in Oregon found a balloon and began tampering with it, causing the bombs it was carrying to explode. As a result five children and a woman were killed.

Each flotilla of balloons was accompanied by a special gas balloon which gave off radio signals which enabled the Japanese to check on their ocean spanning flight. But thanks to the radio and press censorship, they had no idea how successful or otherwise their secret weapon was.

Suddenly in the April of 1945, the balloon attacks ceased. When months passed with no balloon sightings recorded, it was decided that the gas-bag invasion was now really over. Why had the Japanese abandoned using them?

This question was not answered until 1948, when the former Chief of Staff, U.S. Western Defence Command, visited General Kusaba, who had been in charge of the project. The balloon offensive had been abandoned for one seemingly good reason, General Kusaba informed him. The complete absence of any reports on the radio and press over such a long period, had led the Japanese High Command to come to the conclusion that their balloons were not reaching the American Continent, and the operation was put to an end.