West Germany was the informal name for the Federal Republic of Germany from 1949 to 1990, during which years the Federal Republic did not yet include East Germany (formally called the German Democratic Republic (GDR)). Since the German reunification of 1990, the Federal Republic of Germany is informally called simply Germany.
West Germany was proclaimed May 23, 1949, with Bonn as capital, and included the post-World War II UK, US, and French occupation zones. West Germany was declared "fully sovereign" May 5, 1955, although with the former occupying troops remaining on the ground, like the Soviet Army remained in East Germany.
West Germany joined NATO on May 9, 1955, thus becoming a focus of the Cold War with its juxtaposition to East Germany, a member of the subsequently founded Warsaw Pact. The former German capital, Berlin, was also divided into East Berlin and West Berlin but West Berlin was completely surrounded by East Germany.
After the fall of the Berlin Wall on November 9, 1989, the unification of the two Germanies was quickly arranged: formally, West Germany grew by annexing the territory of East Germany, and is now known simply as Germany. This took place on October 3, 1990, and the four occupying powers officially withdrew on March 15, 1991. US forces, however, maintained military bases, such as Ramstein Air Base, Baumholder , and Grafenwöhr.