When was radar first used in world war 2?

Answer 1

One of the first uses was during the Battle of Britain. British radar would detect oncoming German airplanes and the British would send up the Supermarine Spitfire to shoot down fighters and the Hawker Hurricane to shoot down bombers. Radar let the British use their aircraft to their best advantage. Instead of constantly flying air patrol, they could take off when the enemy was coming, and attack them where they were. It was the advantage of radar that enabled the British to defeat the Germans and showed once and for all time, the importance of radar in air combat.

Answer 2

the first practical use of land to air radar was to detect German planes during the battle of Britain, 1940-41. sea to sea radar was used all through the war in various stages and guises