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.
The leaders of the Allies were Franklin Roosevelt (the United States), Winston Churchill (Great Britain), and Joseph Stalin (the Soviet Union).
Variation in the relative frequency of different genotypes in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce.