West Germany is the common English name for the Federal Republic of Germany in the period between its creation on 23 May 1949 and German reunification on 3 October 1990. During this Cold War era, NATO-aligned West Germany and Warsaw Pact-aligned East Germany were divided by the Inner German border. After 1961 West Berlin was physically separated from East Berlin as well as from East Germany by the Berlin Wall. This situation ended when East Germany was dissolved and split into five states, which then joined the ten states of the Federal Republic of Germany along with the reunified city-state of Berlin. With the reunification of West and East Germany, the Federal Republic of Germany, enlarged now to sixteen states, became known simply as "Germany". This period is referred to as the Bonn Republic by historians, alluding to the interwar Weimar Republic and the post-reunification Berlin Republic.
The Federal Republic of Germany was established from eleven states formed in the three Allied Zones of occupation held by the United States, the United Kingdom and France. US and British forces remained in the country throughout the Cold War.