World War II: The main three leaders of the Allied nations, Winston Churchill, Harry S. Truman and Joseph Stalin hold the Potsdam Conference in the German city of Potsdam to decide the future of a defeated Germany.

The Allies, formally referred to as the United Nations from 1942, were an international military coalition formed during World War II (1939–1945) to oppose the Axis powers. Its principal members were the "Big Four" – the United Kingdom, United States, Soviet Union, and China.

Sir Winston Leonard Spencer Churchill was a British statesman, military officer, and writer who was Prime Minister of the United Kingdom from 1940 to 1945 and again from 1951 to 1955. For some 62 of the years between 1900 and 1964, he was a member of parliament (MP) and represented a total of five constituencies over that time. Ideologically an adherent to economic liberalism and imperialism, he was for most of his career a member of the Conservative Party, which he led from 1940 to 1955. He was a member of the Liberal Party from 1904 to 1924.

Harry S. Truman was the 33rd president of the United States, serving from 1945 to 1953. As the 34th vice president in 1945, he assumed the presidency upon the death of Franklin D. Roosevelt that year. Subsequently, Truman implemented the Marshall Plan in the aftermath of World War II to rebuild the economy of Western Europe, and established both the Truman Doctrine and NATO to contain the expansion of Soviet communism. A member of the Democratic Party, he proposed numerous New Deal coalition liberal domestic reforms, but few were enacted by the conservative coalition that dominated the United States Congress.

Joseph Vissarionovich Stalin was a Soviet politician and revolutionary who led the Soviet Union from 1924 until his death in 1953. He held office as General Secretary of the Communist Party from 1922 to 1952 and as the fourth premier from 1941 until his death. Despite initially governing the country as part of a collective leadership, he ultimately consolidated power to become an absolute dictator by the 1930s. Stalin codified the party's official interpretation of Marxism as Marxism–Leninism, while the totalitarian political system he created is known as Stalinism.