Britain, France, the United States, and the Soviet Union occupied Germany at the end of the Second World War. Each country controlled a zone. They also occupied Berlin, which was surrounded by the Soviet zone, and divided the city into four sectors.
Co-operation broke down in 1947 and early 1948. The three Western powers decided to create a separate West German government in their zones. The Soviets tried to dissuade them by gradually escalating harassment of Western traffic to and from the city, which culminated in the Berlin blockade, imposed 24 June 1948.