Barrage balloon

A barrage balloon, sometimes called a "blimp", is a large balloon tethered with metal cables, used to defend against aircraft attack by damaging the aircraft on collision with the cables, or at least making the attacker's approach more difficult. Commonly the designs were kite balloons, having a shape and cable bridling which stabilise the balloon in windy conditions, allowing operation in higher winds than a spherical balloon. Some examples carried small explosive charges that would be pulled up against the aircraft to ensure its destruction. Barrage balloons are not practical against very high-flying aircraft, due to the weight of a very long cable.

France, Germany, Italy and the United Kingdom used barrage balloons in the First World War. Sometimes, especially around London, several balloons were used to lift a length of "barrage net", in which a steel cable was strung between the balloons and many more cables hung from it. These nets could be raised to an altitude comparable to the operational ceiling (14,764 ft/ 4,500 m) of the bombers of the day. By 1918 the barrage defences around London stretched for 50 miles (80 km), and captured German pilots expressed great fear of them.

In 1938 the British Balloon Command was established to protect cities and key targets such as industrial areas, ports and harbours. Balloons were intended to defend against dive bombers flying at heights up to 5,000 feet (1,500 m), forcing them to fly higher and into the range of concentrated anti-aircraft fire—anti-aircraft guns could not traverse fast enough to attack aircraft flying at low altitude and high speed. By the middle of 1940 there were 1,400 balloons, a third of them over the London area.

While dive-bombing was a devastatingly effective tactic against undefended targets, such as Guernica and Rotterdam, dive-bombers were very vulnerable to attack by fighter aircraft while performing a dive, and their use in this role by Germany against the UK with its effective Royal Air Force was rapidly discontinued. Balloons proved to be of little use against the German high-level bombers with which the dive-bombers were replaced, but continued to be manufactured nonetheless, until there were almost 3,000 in 1944. They proved to be mildly effective against the V-1 flying bomb, which usually flew at 2,000 feet (600 m) or lower but had wire-cutters on its wings to counter balloons. 231 V-1s are officially claimed to have been destroyed by balloons.

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