In World War II, the four major Allies were Great Britain, the United States, the Soviet Union and France. Lesser allies included Australia, China, Brazil, Poland, South Africa and Yugoslavia, among others, representing six different continents.
The first countries to stand in opposition to the Axis powers of Germany and Italy were France and Great Britain, who signed a pact to protect Poland in 1939 after Hitler maneuvered to attack it. Secretly, the Soviet Union made a separate pact with Hitler to split Poland between them. However, the Germans double-crossed the Soviets, invading them in June 1941, and the Soviets almost immediately joined the Allied powers. Not until the Japanese, the third major Axis power, bombed Pearl Harbor in December 1941 and Germany and Italy declared war against the U.S. four days later did America enter the Allied ranks.
After the end of World War II, the Allied forces were instrumental in creating the United Nations. The "big three" of Britain, the United States and the Soviet Union joined with a fourth powerhouse, China, to be the "four policemen" of the Allies, each expected to maintain order in their respective regions of the world. With the addition of France, these four nations became the permanent members of the U.N. Security Council.