Prior to the construction of the Berlin Wall in 1961, travel between the Eastern and Western sectors of Berlin was completely 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. East German officials, humiliated by this mass defection, subsequently chose to erect the Berlin Wall in order to prevent residents from leaving East Germany.