Meanwhile, relations between the two “superpowers” deteriorated. In August 1961, in order to stem a growing tide of emigrants fleeing from East to West Berlin, the Soviets constructed a wall separating the two parts of the city. Until its demolition in 1989, the Berlin Wall would stand as a tangible symbol of the Cold War and the division of Europe.

The most dangerous crisis of the Kennedy administration, and in many ways of the entire Cold War, came in October 1962, when American spy planes discovered that the Soviet Union was installing missiles in Cuba capable of reaching the United States with nuclear weapons. The Russians’ motive—whether they hoped to alter the world balance of power or simply stave off another American invasion of Cuba—may never be known. But the Kennedy administration considered the missiles’ presence intolerable. Rejecting advice from military leaders that he authorize an attack on Cuba, which would almost certainly have triggered a Soviet response in Berlin and perhaps a nuclear war, Kennedy imposed a blockade, or “quarantine,” of the island and demanded the missiles’ removal. After tense behind-the-scenes negotiations, Soviet premier Nikita Khrushchev agreed to withdraw the missiles; Kennedy pledged that the United States would not invade Cuba and secretly agreed to remove American Jupiter missiles from Turkey, from which they could reach the Soviet Union.

For thirteen days, the world teetered on the brink of all-out nuclear war. The crisis seems to have lessened Kennedy’s passion for the Cold War. Indeed, he appears to have been shocked by the casual way military leaders spoke of “winning” a nuclear exchange in which tens of millions of Americans and Russians were certain to die. In 1963, Kennedy moved to reduce Cold War tensions. In a speech at American University, he called for greater cooperation with the Soviets. He warned against viewing the Cold War simply as a battle between the forces of light and those of darkness: “No government or social system is so evil that its people must be considered as lacking in virtue.” That summer, the two countries agreed to a treaty banning the testing of nuclear weapons in the atmosphere and in space. In announcing the agreement, Kennedy paid tribute to the small movement against nuclear weapons that had been urging such a ban for several years. He even sent word to Castro through a journalist that he desired a more constructive relationship with Cuba.

New York City train passengers reading the news of President Kennedy’s assassination, November 22, 1963.

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