The United States adopted a neutral position regarding the conflictive events that were already occurring in Europe since the 1930s. They made their stance official with a neutrality act passed by Congress in 1930. However, this stance abruptly changed as two key events occurred:
- The attack of German Submarines against American vessels.
- The attack of Pearl Harbor by the Japanese in 1941.
After the attack of Pearl Harbor, the US decided to enter the war.