On August 13 1961, a grim convoy of tanks and troops wound through eastern Berlin before dawn. By sunrise, East German soldiers had stretched barbed wire across the city, cutting off the Communist sector from the capitalist. A network of concrete walls and electrified fences, guarded by armed men, dogs and minefields soon replaced the wire. Churchill's Iron Curtain metaphor had become a reality.

The 30-mile barrier was built ostensibly to keep out saboteurs and subversives but the Berlin Wall was in fact meant to keep East Germans in. Since 1949, 2.5 million had fled the economic hardships and political repression of Germany's Communist half, creating labour shortages and a "brain drain" of professionals and skilled workers. West Berlin, an island of democracy and capitalism in the midst of East Germany was the principal escape route. In addition, since thousands of eastern-Berliners worked in western Berlin before the wall was built, defectors could easily evade detection.

Through the years, the Soviets had periodically demanded that all Berlin be made a "free city" with both Western and Soviet troops withdrawn. But the Western powers, fearing a total communist take-over, had refused. In June 1961, Khrushchev threatened to use nuclear weapons if the "Berlin question" was not swiftly resolved. When heightening tension accelerated the stampede of illegal emigrants (30,000 East Germans defected in July), the Communist authorities decided to stem the flow by force. The wall was their solution. Henceforth travel eastward was subject to strict restrictions while travel westward was banned.

Though crowds of angry West Berliners confronted the wall builders (only to be dispersed with tear gas and water cannons), and the United States sent in extra troops as a symbolic gesture, fear of retaliation ruled out more forceful measures. A trade embargo against East Berlin was considered but the Communists vowed to blockade West Berlin in response. Eventually, the East Germans encircled all of West Berlin with a fence topped by watchtowers. Travel restrictions for Westerners eased somewhat in the 1980s, but the wall and all it stood for remained intact for nearly three decades.