In June 1961, Nikita Khrushchev called Berlin "the most dangerous place on earth." He knew what he was talking about. Much has been written about the Cuban Missile Crisis a year later, but the Berlin Crisis of 1961 was more decisive in shaping the Cold War-and more perilous. It was in that hot summer that the Berlin Wall was constructed, which would divide the world for another twenty-eight years. Then two months later, and for the first time in history,...