After World War II the Allied forces occupied Berlin. The city was split into sectors: American, British and French on the western side and Soviet on the eastern side. The city administration was a joint council made up of representatives of each of the four Allied powers. The Soviets' aim was to make Germany a socialist state like the rest of eastern Europe. The western Allies of course didn't want this and began developing their sectors of Berlin separate from the Soviet development of eastern Berlin.
As the political friction heated up the Soviets left the joint council in March of 1948. Later that year they made their first attempt at closing the West Berlin borders by denying land access to the west and essentially cutting off their supplies. The Berlin Airlift provided West Berlin with supplies from the Western Allies, and the Soviets released the borders the following year. Germany, however, was irreversably divided, and the Cold War had truly begun. East Germany declared itself the German Democratic Republic or GDR (DDR), followed a few years later by West Germany establishing the Federal Republic of Germany, or FRG.
Over the following decade the economic differences between East and West Berlin were increasingly apparent. The borders remained open and citizens were allowed to cross freely, thousands of East Berliners left for the western sectors. East Berlin's economy was even further damaged by the loss of skilled workers crossing the borders to work in the better economy of West Berlin, and the loss of manpower hampered reconstruction efforts.
Although the rest of the East German/West German border had been closed since 1952 the Berlin border remained open. Amid rumors of closing the border with a wall to prevent further loss of citizens and manpower, GDR Premier Walther Ulbricht denied that anyone had plans to build a wall. Yet just two months later he signed the orders to close the border and build the wall. On the morning of 13 August 1961 West Berliners awoke to find themselves completely surrounded by barricades of barbed wire, anti-tank obstacles and roadblocks. Everything stopped at the wall; streets and train lines were interrupted, utilities were cut off, even families were separated - some with no hope of ever seeing loved ones again.
Almost immediately the GDR began replacing barricades with concrete walls. Three checkpoints were established for approved passage. Soviet propaganda claimed the wall was an 'anti-facist protection wall' for the purpose of protecting the Soviet sector from western aggression. Border guards were ordered to shoot anyone attempting unauthorized crossing to the west. Over the following 28 years this would result in 239 deaths from more than 5000 attempts.
In November of 1989, after months of demonstrations, mass defections via the newly-opened Hungary/GDR border and pressure from Soviet leader Michail Gorbatschow, the GDR opened the FRG border. Tens of thousands of people crossed into West Berlin. In the days that followed millions travelled to West Germany as more checkpoints were set up and the wall began to come down. By mid 1990 East and West Germany began the process of reuniting, and by 1991 most of the Berlin Wall had disappeared. A few sections yet remain, one of which is the Wall Memorial in Bernauer Strasse, and in many places the position of where the wall used to stand is marked by a double row of paving stones.