In perhaps one of the oddest British strategies against Nazi Germany, British troops launched almost 100,000 hydrogen-filled latex balloons into Nazi-controlled territory to set fires and short out power wires as part of Operation Outward.
Women's Auxiliary Air Force members recover a kite balloon.
(Royal Air Force)
Operation Outward was the result of an accident. Barrage and observation balloons in World War I got more coverage than in World War II, but the floating sacks of hydrogen were widely used in both conflicts. You can actually spot them in some of the more famous D-Day photos from later in the day or over the days and weeks that followed.
(The 320th Barrage Balloon Battalion was the only Black combat unit that came ashore on D-Day, though plenty of Black logistic and engineer units were there on June 6.)
But in September 1940, a few British barrage balloons broke free during a storm and drifted across Scandinavia, pissing the Scandinavians all the way off. The steel tethers these balloons dragged behind them had a pesky habit of shorting out power lines and otherwise damaging infrastructure.
A U.S. Army Joint Land Attack Cruise Missile Defense Elevated Netted Sensor System, known as JLENS.
But when it happened in the Scandinavian countries in 1940, the Brits were all, "Wait, what's bad for the goose is bad for the gander, so let's apologize to Scandinavia but then do the same thing, on purpose, to Hitler's Third Reich. Screw those guys."
The British relied on a couple infrastructure advantages for this plan. Britain's electrical grid was more developed, and therefore more susceptible to disruption, but it also featured faster circuit breakers. This meant that Britain's grid, if hit with balloons trailing wires, would suffer relatively little damage. Germany's, with slower breakers, had a real risk of losing entire sections of the grid or even power plants to balloon disruptions.
So, even if it led to a balloon trading war, Britain could expect to hold the upper hand. And so weather balloons were filled with hydrogen, fitted with either spools of wire or incendiary devices, and floated over the channel into Germany.
An "incendiary sock" like those used to burn German towns.
(UK National Archives)
The wires were relatively thin. Experimentation showed the designers that they didn't need the thick steel of normal tethers to short lines, cause electrical arcs, and damage German power distribution. The electrical arcs were the real killer, draining power from the grid, overworking the components of the power generation, and weakening the transmission lines so they would later break in high winds.
Both types were made to fly over the channel at a little over 20,000 feet, then descend to 1,000 feet and do their work. They needed winds of about 10 mph or more to be as effective as possible.
And they worked, well. The idea wasn't to cripple Germany in a single blow, but to cost them more in economic damage and defensive requirements than it cost Britain to deploy them. And, thanks to the low-cost materials Britain used, Britain only had to pay around the U.S.equivalent of .50 per balloon. Shooting a balloon down could cost much more than that in ammo, and that was if it was shot down by air defenders. If fighters had to launch, the fuel and maintenance would be astronomical.
And balloons that weren't shot down could easily do hundreds to hundreds of thousands of dollars worth of damage. In 1942, a balloon launch overloaded a power plant at Böhlen so badly that the plant was completely destroyed. And while the power was off in this and other events, German units were made less ready for combat, and German wartime production was slowed.
Assessments found during and after the war painted a picture of constant disruption on the German side. In occupied France, there were 4,946 power interruptions during the program, most of them caused by the balloons. In 11 months from early 1942 to early 1943, Germany had 520 major disruptions of high-voltage lines.
And at a cost of .50 a balloon plus the wages of balloon launchers, mostly members of the Women's Royal Navy Service, the more than 99,000 balloons launched were a hell of a deal.