Final answer:
U.S. involvement in Vietnam escalated from military advising and covert operations under Kennedy to full military engagement under Johnson. Cold War fears of communism spreading in Southeast Asia influenced these decisions, leading to significant national division and protests. Nixon's secret actions hinted at a desire for victory despite public support for withdrawal.
Step-by-step explanation:
Changes in U.S. Involvement in Vietnam during the Kennedy and Johnson Administrations
During the Kennedy administration, U.S. involvement in Vietnam began as a commitment to bolster South Vietnam's military against the communist North. The U.S. provided advisors and supported covert operations, like the secret bombings in Laos and guerrilla raids by the Hmong. After Kennedy's assassination, President Lyndon Johnson faced the decision to withdraw or intensify U.S. military engagement. Johnson escalated the conflict significantly, sending over half a million soldiers to Vietnam by 1965. This decision was motivated by the Cold War strategy of containment and a fear of the 'domino effect' where nearby nations might also fall to communism. Johnson's policies led to deep national divisions and protests.
The situation evolved further when Nixon entered the scene. Publicly, Nixon supported Johnson's move to initiate peace negotiations and withdraw troops. However, privately, he undermined these negotiations, hoping to achieve a U.S. victory. The war continued until the U.S. withdrawal in 1973, with South Vietnam eventually falling to communist forces in 1975.
These policies were all deeply rooted in the conflict between communism and democracy during the Cold War, which led to the U.S. seeking to prevent the spread of communism in Southeast Asia, resulting in prolonged involvement in the Vietnam War.