The Allies of World War II were the countries officially opposed to the Axis powers during the Second World War. Within the ranks of the Allied powers, the British Empire, the Union of Soviet Socialist Republics, and the United States of America were known as "The Big Three." U.S. President Franklin D. Roosevelt referred to the Big Three and China as the "Four Policemen". France, before its defeat in 1940 and after Operation Torch was considered as a major ally (as free France, fighting France and French force of the interior then as a full nation).

During December 1941, Roosevelt devised the name "United Nations" for the Allies, and the Declaration by United Nations, on 1 January, 1942, was the basis of the modern UN. At the Potsdam Conference of July-August 1945, Roosevelt's successor, Harry S. Truman, proposed that the foreign ministers of China, France, the Soviet Union, the United Kingdom and the United States "should draft the peace treaties and boundary settlements of Europe," which led to the creation of the Council of Foreign Ministers.