In the 1960s and 1970s, the United States remained locked in bitter conflict with communist countries. Most American leaders throughout the period saw the world in Cold War terms and sought to counter the perceived threat of the Soviet bloc. Cuba became a battleground in the Kennedy years.  

Ever since Fidel Castro's revolutionary army seized power in 1959 and gained the support of the Soviet Union, relations with Cuba had been strained. The United States broke diplomatic ties just before Kennedy assumed office, and the Central Intelligence Agency (CIA) began training Cuban exiles to invade their homeland and spark an uprising. The attack at the Bay of Pigs in the spring of 1961 failed miserably. Kennedy, who approved the plan initiated by the Eisenhower administration, accepted responsibility for the defeat.  

The next year, seeking to recoup lost prestige, Kennedy stood firm when he learned the Soviet Union was secretly installing offensive nuclear missiles in Cuba. After considering different options, he decided on a quarantine to prevent Soviet ships from bringing additional missiles to Cuba, and he demanded publicly that the Soviets remove the weapons. After several days of tension, during which the world was closer than ever before to nuclear war, the Soviets backed down. Supporters applauded Kennedy's courage; critics charged that he risked nuclear disaster when quiet diplomacy might have been more appropriate. In retrospect, however, the Cuban missile crisis marked a turning point in U.S.-Soviet relations as both sides saw the need to defuse tensions that could lead to direct military conflict. The following year, the United States, the Soviet Union, and Great Britain signed a landmark Limited Test Ban Treaty, which prohibited nuclear weapons tests in the atmosphere.