Kennedy's closing was both a pledge and a challenge. He committed the United States to never initiating war — a statement of enormous consequence from a president who had overseen the Bay of Pigs invasion and the Cuban Missile Crisis, and who was escalating American involvement in Vietnam. But the speech's final word was not about what America would refrain from doing but what it would actively pursue: 'We shall also do our part to build a world of peace where the weak are safe and the strong are just.' The last sentence — 'Confident and unafraid, we labor on — not toward a strategy of annihilation but toward a strategy of peace' — became the speech's most quoted line. Nikita Khrushchev later told diplomats it was 'the greatest speech by any American President since Roosevelt,' and it directly led to the Limited Nuclear Test Ban Treaty signed that August.