When was the World War 2 radar made?

How many troops fought in battle of D-Day? What was WEB DuBois roleing in civil war? What challenges and hardships were faced by civil war soldiers? Battles over the control of straits are often related to the control of? How did the north pay for the war effort? Did rifles kill many of the soldiers in the civil war? What was the norths population during the American Civil War? What world war 2 group wore the insignia of a pale blue stone arrowhead with the letter 'T' in the center? Why did US attack Normandy in World War 2? President lincoln and johnson were wise in not seeking harsh treatment of the southern states? How did soldiers keep cheerful in ww1? Why did the Battle of Midway happen? Representatives of every Allied nation except which country attended the peace conference in Paris? What were the causes of operation desert storm? What does a dragon mean on a coat of arms? The great migration during world war 1 was a flow of? What was the percentage of buildings damaged and destroyed in World War 2? Which supports the idea hat France was first unsure about who would win the war? What strategy did the United states use in fighting the Japanese in the pacific? Who wrote the Farewell to Arms in the 1920's?