Following the defeat of Nazi Germany in World War II, the Soviet Union engineered the installation of communist regimes in most of the countries occupied by Soviet military forces at the end of the War, including Poland, Hungary, Czechoslovakia, Bulgaria, Romania, and the GDR, which together with Albania formed the Comecon in 1949 and later a military alliance, the Warsaw Pact.By the early 1950s, the Soviet approach to controlling national movement, restricting emigration, was emulated by most of the rest of the Eastern Bloc, including East Germany. The restrictions presented a quandary for some Eastern Bloc states, which had been more economically advanced and open than the Soviet Union, such that crossing borders seemed more natural—especially where no prior border existed between East and West Germany.Up until 1952, the demarcation lines between East Germany and the western occupied zones could be easily crossed in most places.