The Problem of Berlin
A border, similar to that between East & West Germany, was created around the edge of the US, UK and French sectors of Berlin.
The border between the western sectors of Berlin and East Germany
However, the border between the Soviet sector of Berlin and the western sectors which ran through the streets of the city remained unfortified.
It was therefore quite straightforward for an East German to travel to Berlin and then walk or ride the U-Bahn or S-Bahn into the western sectors.
The diagram shows that you could travel into the Soviet sector from any part of East Germany and then cross the border into West Berlin.
As the numbers crossing continued to increase, efforts were made to stop any obvious attempt to cross into West Berlin.
This image is dated 1955 and shows the standoff created by a young women's (successful) attempt to cross the border into West Berlin
In West Berlin the East Germans were given new paperwork and then flown out of the city into West Germany using one of the western airlines.
Would be emigrants were given new papers and flown to West Germany
It has been estimated that between 1949 and 1961 aproximately 3.5 million East Germans emigrated to the West – 1/6 of East Germany's entire population - 207,000 left in the first seven months of 1961.
Most of the emigrants continued to be the young and educated. The loss was disproportionately heavy among professionals—engineers, technicians, physicians, teachers, lawyers and skilled workers.
Many farmers also fled to the west leaving large areas of land (10% of the total) uncultivated which in turn led to food shortages.
The East German economy was on the verge of collapse and drastic measures were required to stem the flow of emigrants.