1) After WWII, Germany was divided into four occupied zones controlled by the US, UK, France and Soviet Union. Berlin was similarly divided. 2) In 1948, the Soviet Union blocked land access to the western sectors of Berlin, prompting the US and UK to launch the Berlin Airlift to supply the city from the air. 3) In 1961, the East German government built the Berlin Wall to prevent East Germans from fleeing to the western sectors and West Germany. It remained until 1989 when rising dissent led East Germany to open border crossings and allow East Berliners to travel freely.