USA HISTORY

Detailed explanation-1: -In World War II, the three great Allied powers-Great Britain, the United States, and the Soviet Union-formed a Grand Alliance that was the key to victory. But the alliance partners did not share common political aims, and did not always agree on how the war should be fought.

Detailed explanation-2: -The most important factor in swaying the Soviets eventually to enter into an alliance with the United States was the Nazi decision to launch its invasion of the Soviet Union in June 1941.

Detailed explanation-3: -The Soviet Union, which initially had a nonaggression pact with Germany and participated in its invasion of Poland, joined the Allies in June 1941 after Operation Barbarossa, the German invasion of the Soviet Union.

Detailed explanation-4: -Signed on May 14, 1955, the Warsaw Pact established the Warsaw Treaty Organization, a mutual defense alliance that was originally composed of the Soviet Union, Albania, Bulgaria, Czechoslovakia, East Germany, Hungary, Poland, and Romania.

Detailed explanation-5: -… World War II the chief Allied powers were Great Britain, France (except during the German occupation, 1940–44), the Soviet Union (after its entry in June 1941), the United States (after its entry on December 8, 1941), and China.