Question

During World War II, the United States and the Soviet Union were united in

Answer 1

...fighting Nazi Germany.

Answer 2

That's a little tricky. The Soviet Union began the Second World War as an ally of Nazi Germany. That's how the war started -- with Germany invading Poland from the west, and the Soviet Union from the east. However, after Germany invaded the USSR in 1942, that pact was broken, and the USSR gladly allied itself with the West against Germany. It's the later alliance to which you probably refer.

Answer 3

in WWII but in order to end the war they dropped an atomic bomb in japan