The arms race between the Soviet Union and the United States was the most dangerous confrontation in the history of the world. Nikita Khrushchev's decision to place nuclear missiles in Cuba, and John F. Kennedy's willingness to call his bluff, brought the Soviet Union and the West to the edge of a cataclysmic nuclear war. Kennedy's confidence in his brinkmanship hung on evidence provided by Oleg Penkovsky, the MI6/CIA agent inside Soviet military...