<P> 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 . </P>
what were the blimps used for in ww2 in london
to defend against dive bombers flying at heights up to 5,000 feet ( 1,500 m )