Cold War: The American and British occupation zones in Allied-occupied Germany, after World War II, merge to form the Bizone, which later (with the French zone) became part of West Germany.

The Cold War was a period of global geopolitical rivalry between the United States (US) and the Soviet Union (USSR) and their respective allies, the capitalist Western Bloc and communist Eastern Bloc, which began in the aftermath of the Second World War and ended with the dissolution of the Soviet Union in 1991. The term cold war is used because there was no direct fighting between the two superpowers, though each supported opposing sides in regional conflicts known as proxy wars. In addition to the struggle for ideological and economic influence and an arms race in both conventional and nuclear weapons, the Cold War was expressed through technological rivalries such as the Space Race, espionage, propaganda campaigns, embargoes, and sports diplomacy.

The entirety of Germany was occupied and administered by the Allies of World War II, from the Berlin Declaration on 5 June 1945 to the establishment of West Germany on 23 May 1949. Unlike occupied Japan, Nazi Germany was stripped of its sovereignty and its government was entirely dissolved. After Germany formally surrendered on Tuesday, 8 May 1945, the four countries representing the Allies asserted joint authority and sovereignty through the Allied Control Council (ACC).

The Bizone or Bizonia was the combination of the American and the British occupation zones on 1 January 1947 during the occupation of Germany after World War II. With the addition of the French occupation zone on 1 August 1948 the entity became the Trizone. Later, on 23 May 1949, the Trizone became the Federal Republic of Germany, commonly known as West Germany.

West Germany was the common English name for the Federal Republic of Germany (FRG) from its formation on 23 May 1949 until its reunification with East Germany on 3 October 1990. It is sometimes known as the Bonn Republic after its capital city of Bonn, or as the Second German Republic. During the Cold War, the western portion of Germany and the associated territory of West Berlin were parts of the Western Bloc. West Germany was formed as a political entity during the Allied occupation of Germany after World War II, established from 12 states formed in the three Allied zones of occupation held by the United States, the United Kingdom, and France.