Answer:
Because they were allied against Nazi Germany
Explanation:
After defeating France and almost all of Europe, on June 22nd, 1941, Nazi Germany declared war on the USSR. Since the USSR had signed a non aggression pact in 1939 when invading Poland, the USSR was 100% surprised. They had astounding victories, but had to stop their advance due to the snow and mud during the winter. Then came Pearl Harbor. On December 7th, 1941, the Empire of Japan attacked a United states naval base in order to resume their conquest. They did this because the United States posed economic sanctions on Japan, limiting their oil supply. But then, on December 11th, 1941, Nazi Germany declared war on the United States(even though they never had to). This then lead to the Axis powers leaving Africa, most of southern Italy, and their Russian Eastern territory. When the landings on Normandy beach, western France, and Southern France, the Nazis were totally surrounded. When the USSR finally captured Berlin, Germany surrendered. This then made the United Kingdom, The United States, The USSR, and France(kind of since they surrendered) victors.
