Radar in World War II greatly influenced many important aspects of the conflict. In the United States, the technology was demonstrated during December The U. Navy fielded the first of these in early , and a year later by the U. Navy in , and the term "radar" became widely used. While the benefits of operating in the microwave portion of the radio spectrum were known, transmitters for generating microwave signals of sufficient power were unavailable; thus, all early radar systems operated at lower frequencies e.
In February , Great Britain developed the resonant-cavity magnetron , capable of producing microwave power in the kilowatt range, opening the path to second-generation radar systems. After the Fall of France , Britain realised that the manufacturing capabilities of the United States were vital to success in the war; thus, although America was not yet a belligerent, Prime Minister Winston Churchill directed that Britain's technological secrets be shared in exchange for the needed capabilities.
In the summer of , the Tizard Mission visited the United States. It was times more powerful than anything they had seen. The magnetron was later described by American military scientists as "the most valuable cargo ever brought to our shores". Robert A. Watson-Watt at the Radio Research Station, Slough, was asked to investigate a radio-based "death ray". In response, Watson-Watt and his scientific assistant, Arnold F. Wilkins , replied that it might be more practical to use radio to detect and track enemy aircraft.
On 26 February , a preliminary test, commonly called the Daventry Experiment , showed that radio signals reflected from an aircraft could be detected. Research funds were quickly allocated, and a development project was started in great secrecy on the Orford Ness Peninsula in Suffolk. Bowen was responsible for developing the pulsed transmitter. On 17 June , the research apparatus successfully detected an aircraft at a distance of 17 miles.
In August, A. While this operation was under the Air Ministry, the Army and Navy became involved and soon initiated their own programs.
