The invention of radar had a huge impact on how the Second World War was fought on both sides. Radar is a very basic way of obtaining information and because it is simple it makes it highly adaptable—during the war scientists and engineers found dozens of ways of using it.

Bombing was the major concern. Enemy bombers could carry huge amounts of bombs and there was little to prevent enemy aircraft from reaching a nation’s cities. With radar such air attacks could be picked up before the bombs started dropping. Radar was an ‘early warning system . When the bombers approached fighter aircraft could be mobilized to attack them and citizens could be warned to take shelter.

Radar works by sending out radio waves and detecting any reflections from distant objects. In 1904 the German Christian Hülsmeyer patented a means to do this, but the invention attracted very little interest. But in the late 1930s many countries including France, Germany, Italy, Japan, Netherlands, the Soviet Union, the United Kingdom, and the United States all independently developed radar. Even before the outbreak of war Britain had built an air-defence radar system called Chain Home.

Many other uses were found for radar during the war. It was used to aim searchlights, then to aim anti-aircraft guns. It was put on ships, where it was used to navigate at night and through fog, to locate enemy ships and aircraft, and to direct gunfire. It was put into airplanes, where it could be used to locate hostile aircraft or ships, or to navigate the aircraft, or to find bombing targets. Radar could be used to locate enemy artillery and even buried mines. Military meteorologists used radar to track storms.