Final answer:
Richard Nixon's foreign policy differed from his predecessors by employing a policy of detente and shifting the responsibility for allies' defense, which contrasted Kennedy's and Johnson's direct military interventions. Nixon sought to ease Cold War tensions through diplomatic engagement and the Nixon Doctrine, while also secretly extending the Vietnam War.
Step-by-step explanation:
President Richard Nixon's foreign policy significantly diverged from that of his immediate predecessors, Presidents John F. Kennedy and Lyndon B. Johnson. While Kennedy and Johnson had escalated U.S. involvement in Vietnam as a part of their containment strategies against communism, Nixon sought to realign U.S. foreign policy through a balance-of-power approach and also began to implement a new policy of detente. This approach was designed to ease Cold War tensions, especially with the Soviet Union and China, through diplomatic engagement, negotiation, and arms control measures like the Strategic Arms Limitation Talks (SALT).
Nixon's introduction of the Nixon Doctrine indicated a shift in U.S. foreign policy from direct military intervention to a stance where the United States would support its allies but not bear the primary responsibility for their defense. This was a stark contrast to the direct military involvement prevalent during the Kennedy and Johnson administrations.
Despite his public commitment to peace, privately Nixon believed that North Vietnam could still be defeated even after inheriting a war that the American public had grown weary of. In contrast to the public de-escalation by Johnson, Nixon sought to turn the tide of the war in Vietnam by secretly disrupting peace talks to gain a more favorable position, thereby extending the war. While he continued the space exploration efforts initiated by Kennedy and Johnson, resulting in the Apollo moon landing, he primarily focused on his versions of realpolitik and detente in foreign affairs.
Nixon's policies developed an environment for dialogue with adversaries that his successor, Gerald Ford, sought to continue, particularly with the Soviet Union. However, Ford experienced limited success due to Congressional opposition. Meanwhile, post-Vietnam, Congress passed the War Powers Resolution to restrict the presidential power to wage war without Congressional approval, a direct response to Nixon's handling of the Vietnam War.