A barrage balloon is a large uncrewed tethered balloon used to defend ground targets against aircraft attack, by raising aloft steel cables which pose to hostile aircraft a severe risk of collision, making the attacker's approach difficult and hazardous. Early barrage balloons were often spherical. The kite balloon, having a shape and cable bridling which stabilises the balloon and reduces drag, could be operated at higher wind speeds than could 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 high-altitude aircraft. The long cable required for a high-altitude balloon would be too heavy. First World War France, Germany, Italy and the United Kingdom used barrage balloons in the First World War. While the French and German forces developed kite balloons, early British barrage balloons were spherical.Sometimes, especially around London, several balloons were used to lift a length of "barrage net": a steel cable was strung between the balloons and more cables hung from it. These nets could...