The early years of World War Two caused chaos and devastation throughout Europe. The 1939 non-aggression pact between the Germans and Russians had promised safety for the Soviet Union, but Hitler was not to be trusted. With the invasion of Soviet territories in 1941, a new and unexpected "Grand Alliance" was formed between the United Kingdom, United States, and the Soviet Union.

The war in Europe was over, but heavy fighting continued in the East, and President Truman was desperate to bring the war to a close in the Pacific theatre. With the US Manhattan Project successfully testing the first nuclear bomb in July 1945, the US no longer needed Soviet help to overpower the Japanese forces who were dominating in the region.