Germany’s “sausage” balloon’s appearance was mocked, but the Drachenballon (or kite balloon) was heavily deployed during WWI.
It was a valuable asset for intelligence gathering and artillery spotting.
And unlike the traditional spherical balloon, its unique shape enabled it to face the wind, rather than being blown around by it.
It soon went into mass production and was sold to several countries for military observation.
Balloons have a long, strange history of being weaponised or used for tracking and surveillance.
And it appears today they are having a renaissance.
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Early last year, a seven-day saga played out in the skies when a suspected Chinese spy balloon took a trip through US airspace.
During recent months, North Korea has allegedly launched hundreds of rubbish-laden balloons across their heavily fortified border into South Korea.
And this week, the US Army put out a renewed call for sophisticated sensing technology it could attach to a fleet of balloons it intends to send into the stratosphere.
But despite new technology possibilities, hot-air snooping and terrorising tactics remain largely the same.
Japan’s ‘Fu-Go’ balloon bombs
Japan went to great effort in WWII getting project “Fu-Go” off the ground.
The grand plan was to create balloon bombs to terrorise American citizens and divert US military resources to a domestic crisis.
The balloons were designed to be carried by winds in the upper atmosphere over the Pacific Ocean to North America, then ignite devastating forest fires across the western states.
Thousands of Japanese schoolgirls were enlisted to hand-stitch and paste more than 10,000 balloon envelopes — the part of the balloon that fills with hot air.
The massive envelopes had a 32-metre circumference made from rubberised silk, and lightweight bark tree “washi” paper.
Today, the delicate Japanese washi paper is mainly used for traditional arts or things such as shoji sliding doors.
Hanging below the balloon was an elaborate “chandelier”, carrying several incendiary bombs, a 15 kg anti-personnel bomb, fuses, switches and a ring of 3 kg sandbags.
On November 3, 1944, the first 6,000 bomb-laden balloons lifted off.
Records vary, but during the next six months, it’s estimated another 6,000 were launched towards North America.
About 1,000 are believed to have reached the continent, but there were only 285 reported incidents, one of which was fatal.
In May 1945, a pregnant woman and five children were killed when they came across a balloon in the woods in Oregon.
Robert Mikesh, the former senior curator of the National Air and Space Museum, wrote in a scholarly report on the Fu-Go balloons that witnesses described seeing “giant jellyfish” in the sky.
Mikesh said the balloons were an “interesting experiment” but the project was considered a military failure.
“The effort and expense by the Japanese in the balloon offensive was great in comparison to the minor results achieved,” he wrote.
“The greatest weakness of the free balloon as a military weapon is that it cannot be controlled.”
Britain’s barrage balloons
A more successful use of hot-air weaponry during the Second World War, was the so-called barrage balloons.
The silver oval-shaped balloons were used to protect urban centres and other important locations, such as ports and factories.
At about 18m long and 7m in diameter, they floated up to 1,500m in the air to defend against enemy bomber aircraft.
Britain’s Royal Air Force (RAF) Balloon Command used them to defend against Germany’s Luftwaffe, as their trailing metal cables would severely damage or destroy any aircraft that touched them.
And any attempt to shoot down the balloon would put aircraft at risk of being caught in an explosion of hydrogen.
By 1944, the RAF had several thousand of the balloons.
They could be flown from ships or barges at sea, and played a vital role in the D-Day Normandy Invasion.
Thousands were inflated in England and attached to ships making the trip across the English Channel.
An iconic photo from 1944 shows ships lining the Normandy shore with a fleet of barrage balloons floating overhead.
Why balloons are making a comeback
Today, militaries have again been experimenting with hot-air enabled capabilities.
The high-altitude balloons (HABs), or the more blanket term high-altitude pseudo satellites (HAPS), are intended to float in the stratosphere.
Sitting higher than 18km and to up to 50km, it’s the area between the atmosphere and space often referred to as “near space”.
HABs have been described as the missing link between drones flying closer to the ground and satellites in space.
Peter Layton, an aviation and defence expert and visiting fellow at the Griffith University Asia Institute, said military interest in recent years is due to cheaper and more powerful technology.
“Digital technology is much more sophisticated, much smaller, requires much less power,” he told the ABC.
“The payloads they put in these balloons are light, cheap, affordable and throw-away.”
The technology can provide continuous coverage of a target area for long periods of time, and get closer to targets than satellites.
They can be fitted with a diversity of sensors, and use low-cost radar systems that produce high-quality imagery.
And they can connect to networks of thousands of satellites like Starlink overhead.
“You’ve got internet connectivity to these balloons which no one’s ever had before,” Dr Layton said.
“These things produce vast amounts of information.”
He added that a better understanding of stratospheric winds was also enabling the balloons to be controlled and stay in roughly the same area for extended periods.
And they can generate power, and extend their life, by carrying solar panels.
Where to now?
The stratosphere is above controlled airspace.
So not only are balloons often difficult to spot, they have a tendency to pop-up unexpectedly — and far from home.
Dr Layton says this is definitely part of their military appeal.
Around December last year, China began sending hundreds of balloons over several weeks directly through Taiwan’s territorial airspace.
Taipei said the balloons were threatening aviation safety and China was using them as an attempt at psychological warfare.
But China’s government repeatedly dismissed the complaints, saying they were for meteorological purposes.
The country gave a similar explanation when a suspected Chinese spy balloon appeared in North American airspace early last year.
The Chinese Foreign Ministry denied any claims of spying, saying it was a meteorology research balloon that had steered off track.
But after it was shot down by a US fighter jet, leaked Pentagon analysis revealed the balloon was carrying equipment that was “excessive for a weather balloon”.
At the time, the Pentagon revealed that during the past several years, Chinese balloons had previously been spotted over countries across five continents.
The US has also been developing and testing its own network of high-altitude balloons for gathering intelligence, electronic warfare jamming, and to eventually track and defeat hypersonic weapons.
The Pentagon dedicated $US27.1 million ($40.3 million) in fiscal year 2023 on multiple ongoing HAB efforts, and aims to test flight a fleet in 2025.
The army is planning to create a multiple sizes with varied sensing capabilities, alongside very-high-flying glider-like drones with extreme endurance.
Last month, the US and partners carried out HAB launches from Guam international airport, as part of field training exercise in the Indo-Pacific region.
“The HAB systems include electromagnetic spectrum sensors and radio networking equipment, which will enable maritime domain awareness,” the US Army said in a statement.
(US Army Pacific)
Australian companies have been working with partners including RMIT University and the RAAF Air Warfare Centre on HAP technologies and prototypes.
But Dr Layton said balloons were yet to become a main focus for the Australian military.
He said balloon hype comes and goes, and is skeptical whether HABs will prove to be more valuable than satellites in the long-run.
Balloons are cheaper to launch, but they face more risks placed in the stratosphere.
“People get a rush of blood to the head and decide that balloons are the latest new thing,” Dr Layton said.
“But at the end of the day, we’ve got these mega constellations of satellites staying overhead for long periods of times, whereas balloons are still hard to anchor in a particular spot.”