The Allied Powers, or Allies, refers to coalitions of primarily North American nations victorious over rival, central-European forces in World War I and World War II. The four nations that recurred as the main forces of the Allied Powers in both wars were France, Russia/USSR, the United Kingdom and the United States.
The antagonists of the Allied Powers in World Wars I and II were coalitions begun by Germany, the Central Powers and Axis Powers, respectively. Italy, though an Allied Power during World War I, joined the Axis Powers under the leadership of Benito Mussolini, only to depose Mussolini in 1943 and fight the German occupation of their northern territories. The inclusion of Japan into the Axis Powers made China join the Allied Powers. Otherwise, the history of formal treaties and informal relationships between the countries of the Allied Powers kept the majority of the coalition intact through both wars.