Ah, the Cold War - 24 hour alerts, bombers on standby, bomb shelters under houses, tank commanders at the Fulda Gap. And the Navy standing ready.
The effect of the differences between the promise of socialist and communist paradises and the grim reality caused (and continues to cause) mass migrations of people flowing away from such "people's republics."
Not surprisingly, the leaders of these alleged Utopian societies decided that only by halting the flow of such refugees could the people come to appreciate how splendid life could be under the "guidance" of those - um- "enlightened ones" who knew the true path.
Thus, everything that could be done to keep people in was done, fences, armed border guards looking inward with orders to shoot to kill, mine fields, travel passes, informers . . .
But there were always defectors . . . so there were more walls, including the Berlin Wall the ultimate symbol of the Cold War.
By the way, before the Wall dividing Berlin, there was an effort by the Soviets to blockade Berlin - shutting off all access by land routes. This effort was thwarted by the Berlin Airlift.
If you have the time, here's an excellent film about the effort it took to defeat the Soviet power grab, featuring Montgomery Clift and Paul Douglas and many of the real airmen, including Navy crews, and allied forces that flew some 28,000 missions to keep West Berlin fed for almost a year - from June 24, 1948 to May 12, 1949 - "The Big Lift" -