History's milestones are rarely so neatly arrayed as they are this summer. Fifty years ago this month, the Berlin Wall was born. After some hesitation, Nikita Khrushchev, the Soviet Union's leader, allowed his East German counterpart, Walter Ulbricht, to erect a barrier between East and West Berlin in order to ensure the survival of communism in the entire Soviet bloc.

By that point, East Germany had hemorrhaged 3 million people — including many of its most talented — as hundreds each day walked into the zones of Berlin controlled by the United States, the United Kingdom, and France.

And 20 years ago this month, hardliners in the Soviet government attempted to overthrow President Mikhail Gorbachev, who, two years after U.S. President Ronald Reagan memorably called on him to "tear down this wall," had done just that. Somewhat miraculously, a reformer who wanted Russians to be part of the democratic West had come to power in the Kremlin.