The Berlin border crossings were created as a result of the postwar division of Germany. Prior to the construction of the Berlin Wall in 1961, travel between the Eastern and Western sectors of Berlin was totally uncontrolled, although restrictions were increasingly introduced by the Soviet and East German authorities at major crossings between the sectors. This free access, especially after the closure of the Inner German border, allowed the Eastern Bloc emigration and defection to occur which resulted in the erection of the Berlin Wall.
After the construction of the Berlin Wall in 1961, border stations between East Berlin, regarded as its capital by the German Democratic Republic but unrecognized by the Western Allies, and the sectors controlled by those three Western Allies were created. Although there were few crossings at first, more sites were built to an increasing extent over the wall's lifespan. Many crossed the wall illegally, climbing over it, sailing around it, or digging under it, while many others died while attempting to cross.
Between West Berlin and German Democratic Republic territory, the border stations were developed very effectively on the GDR's side. (The official designation for controlled border traffic was Grenzübergangsstelle, GÜSt: border crossing site.) Border officials and customs agents would monitor incoming and outgoing traffic according to established procedures, at times with the utmost scrutiny. A strict division of labor among the various organizations was the rule. The security of the outward-facing border and of the border crossings was maintained by special security divisions of the GDR border guard troops (German abbreviation SiK, short for Sicherungskompanien). On 26 May 1952 the East German government decided to close the border and to build up a frontier area between East and West Germany and between West Berlin and East Germany. After 26 May 1952 there was only one quite safe way to escape to the West: Berlin. Although many border crossing points were closed in Berlin and controls at the border happened, it was quite easy to leave the Eastern sector of Berlin to the Western sector. Many East German citizens went to Berlin, bought a S-Bahn (suburban train) or U-Bahn (subway) ticket and left East Berlin.