If other countries aren't willing to fight for them and they cant fight for themselves the United States probally would but no we dont have to
Answer:
Radar
Explanation:
Radar technology employs the use of radio waves in determining the distances speed and location of certain objects. This was instrumental during the war as it helped countries foil secret attacks being planned.
It was used to operate anti-aircraft guns and was used on ships for easy navigation at night and to locate enemy ships and aircraft.