A barrage balloon is a large balloon filled with a gas that is lighter than air and then anchored in a strategic location to deter low-flying enemy aircraft. The barrage balloon was developed in the years leading up to the Second World War, and rarely used after the war, since the design had a number of major flaws and drawbacks. However, there were some instances in the war in which barrage balloons proved to be very helpful, and the balloons became a common sight in the air over potential military targets, especially in Britain.
Barrage balloons were made from sturdy materials and anchored to the ground with the use of long cables. The cables could be winched to vary the height of the balloon, and in some cases, barrage balloons were mobile, designed to be moved around as needed. Some included attached netting, while others were sent aloft with cables alone, and a few were mounted with explosives so that approaching aircraft would be destroyed if they blundered into a field of barrage balloons.
There were several functions to a barrage balloon. The primary goal was to deter low-flying aircraft, making it harder for the enemy to access an area. By forcing planes to fly high, barrage balloons also reduced accuracy in World War Two bombers, and they tended to take away some of the surprise element of attacking aircraft. Barrage balloons rarely actually caught planes in their cables and nets, acting as a psychological barrier more than a physical one. German planes were also outfitted with cable snips which were used to cut through the cables of barrage balloons.
The cable limited the functionality of barrage balloons by making it impossible to fly a barrage balloon at high altitude. As a result, many air forces simply took to ordering high altitude flights, assuming that barrage balloons would be present near their targets and flying above their reach. On occasion, the balloons also escaped, wreaking havoc as they wrapped their cables around utility lines and buildings, and this was a serious drawback to the barrage balloon design. Barrage balloons also reduced the accuracy of ground-based defenses like antiaircraft guns, making it hard for communities to defend themselves when supporting friendly air forces were not present.
After the Second World War, barrage balloons were retired and replaced by other defensive technology. Today, bombers can fly at very high altitude and still deliver very accurate payloads, and weapons can also be detonated remotely, making a field of barrage balloons largely useless against enemy attacks.
