Berlin: The refugee problem
Following the division of Germany into sectors there was ongoing migration from the East to the West. At first some of this was enforced by the Soviets as they moved people on who were likely opponents of their rule. This initial migration was clearly not an issue for the Soviets but later migration was, it severely undermined their ability to run East Germany as they wanted to.
Between the end of the war and 1950 some 15 million people migrated from the Soviet Sector into Western Germany. There was little in place to stop people moving between the sectors and it was quite easy for East Germans to apply for, and get, political asylum once they were in the West. In the early 1950’s this trend of migration continued. Almost 200,000 applications for asylum were made in 1950; 165000 in 1951; 182000 in 1952 and 331000 in 1953 (source: wikipedia).
This level of migration was a problem for the Soviet Union. A large percentage of the migrants were skilled professionals and the remainder left the East short of workers. In 1952 the East Germans decided to reduce the migration. They did this by closing the internal borders between the East and Western sectors. However within Berlin, it was still easy to move from one sector to another. Whilst migration became harder for some, Berlin acted as a route to the West that was used by some 3.5 million Eastern Europeans before 1961.
By 1961 the continued migration was having a major negative impact on the economy and society in Eastern Germany. Something had to be done to stop it.