of the American, British, and French zones, excluding those three countries' zones in Berlin, while the Marxist-Leninist German Democratic Republic was proclaimed in East Germany. West Berlin officially remained an occupied city, but as a corpus separatum it politically was very closely aligned with Federal Republic of Germany despite Berlin's geographic location within East Germany. West Berlin issued its own postage stamps, which were often the same as West German postage stamps but with the additional word "Berlin" added. Airline service to West Berlin was granted only to American, British, and French airlines.
The founding of the two German states increased Cold War tensions. West Berlin was surrounded by East German territory and East Germany proclaimed East Berlin (described as "Berlin") as its capital, a move that was not recognized by the western powers. Although only half the size and population of West Berlin, East Berlin included most of the historic center of the city. The West German government, meanwhile, established itself provisionally in Bonn.
As a result of the political and economical tensions brought on by the Cold War, on 13 August 1961, East Germany began building of the Berlin Wall between East and West Berlin and similar barriers around West Berlin, and events escalated to a tank standoff at Checkpoint Charlie on 27 October 1961. West Berlin was now de facto a part of West Germany with a unique legal status, while East Berlin was de facto a part of East Germany.
Berlin was completely divided. Although it was possible for Westerners to pass from one to the other (but only through strictly controlled checkpoints) for most Easterners, travel to West Berlin or West Germany was no longer possible. In 1971, a Four-Power agreement guaranteed access to and from West Berlin by car or train through East Germany and ended the potential for harassment or closure of the routes.
In 1989, with the end of the Cold War and
