John F. Kennedy died on 22 November 1963, the victim of an assassin's bullet. He had been president just over three years and at the time of his premature death was gearing up for his reelection campaign. A short-lived détente between the United States and the Soviet Union emerged during the final year of Kennedy's presidency. Had he lived, the more developed détente that emerged roughly a decade later may have occurred earlier. During his final year as president, Kennedy was no longer a status quo cold warrior. Following the Cuban Missile Crisis, he charted a new course, determined to avoid a similarly dangerous moment. He chose to engage the Soviet Union and opted for interaction that was safer and seemingly more rational. This brief détente in 1963 had the potential to continue and develop into a more substantial, systemic association based on the avoidance of nuclear war. The Limited Test Ban Treaty of 1963 that Kennedy championed was a precursor to many forthcoming agreements. Although later policy-makers concluded these agreements with the Soviet Union, Kennedy laid the groundwork and set the tone for greater cooperation which led to those diplomatic successes.

This dissertation utilizes newly released documents, oral histories, foreign archives, and the Kennedy Oval Office recordings to examine how Kennedy spent his final year establishing a framework in which he could test his new approach to relations with the Soviet Union and explains how his death resulted in multiple missed opportunities to significantly alter the course of the Cold War. This treatment examines Kennedy's actions in the aftermath of the Cuban Missile Crisis, in consideration of options regarding resolving the status of Berlin, the pursuit of disarmament, and in US relations with the British, French, West Germans, and Soviets. The impact of the Sino-Soviet split on US and Soviet policies is also taken into account.

This study considers Kennedy's successes, such as the Peace Speech, including its origins, delivery, and reception; Kennedy's European trip in June; the various aspects of the Limited Test Ban Treaty, including the selection of Averell Harriman to lead the American diplomats, interaction with the British team, the negotiations with the Soviets, the treaty's signing, and its ratification by the Senate; as well as examples of Kennedy's further initiatives, such as the Hot Line, cooperation with the Soviets in space, the wheat deal, and Kennedy's tempered reaction to the Berlin autobahn incidents. Kennedy's foreign policy emphasis in the build up to his reelection campaign, and Johnson's succession, call attention to the expressed continuity between the two administrations, and the ultimate effect of Kennedy's third year. The conclusions presented here are relevant to the analyses of the Cold War's end and the implications of continued nuclear dissemination.