A barrage balloon is a large balloon used as a defence against aircraft. The balloon is attached to the ground with metal cables, which are intended to ensnare the aircraft, notably its propellers. Some versions carried small explosive charges that would be pulled up against the aircraft to ensure its destruction. Barrage balloons were only really successful for low-flying aircraft, the weight of a longer cable making them impractical for higher altitudes.

In 1938 England set up the Balloon Command to protect British cities and key targets such as industrial areas, ports and harbours. They were intended to serve as a defense against the dive bomber, flying at heights up to 5,000 feet, forcing the aircraft to fly higher and into the range of concentrated anti-aircraft fire. By the middle of 1940 there were 1,400 balloons, a third of them over the London area, where they proved largely useless against the German level bombers that flew right over them. Construction continued however, and in 1944 there were almost 3,000 such balloons. They proved to be particularily effective against the V-1 flying bomb, which tended to fly at 2,000 feet or lower, and claimed about 100 V-1's destroyed.

Many bombers were equipped with devices to cut these cables. It was the British that employed the most barrage balloons, so correspondingly it was the Germans that developed the most capable cable cutters. Their systems consisted of small C-shaped devices attached to the leading edge of the wing, when a cable entered it after sliding down the wing it would trigger a small explosive charge that drove a blade through the cable. British bombers were also equipped with such devices, but the Germans tended not to use a balloon barrage.