In 1948, the Soviet Union began to restrict access to West Berlin, which led to the Berlin Airlift, in which the United States, Britain, and France flew in supplies to the city. The airlift was successful in preventing the Soviets from taking over West Berlin, and the city remained under Allied control until the reunification of Germany in 1990.
The division of Berlin into East and West was a major source of tension during the Cold War. East Berlin was the capital of the German Democratic Republic (GDR), a communist state, while West Berlin was a capitalist enclave within the GDR. The two cities were separated by the Berlin Wall, a heavily fortified barrier that prevented people from crossing between the two sides.
The Berlin Wall was a symbol of the division of Germany and the Cold War. It was torn down in 1989, and Germany was reunified in 1990.