Final answer:
All presidents listed contributed to Vietnam's involvement under containment policy, but Kennedy's full intentions are debated, with some historians believing he might not have escalated to full-scale military intervention.
Step-by-step explanation:
All the presidents listed played a role in the American involvement in Vietnam as part of their adherence to the containment policy, except perhaps John F. Kennedy, whose ultimate intentions regarding Vietnam are subject to debate. Harry S. Truman initiated American involvement by sending military advisers and aid to support France against the Viet Minh. Dwight D. Eisenhower continued funding the French effort and supported South Vietnam after the Geneva Accords. Lyndon B. Johnson chose to fully engage the U.S. military against the Communists in North Vietnam following Kennedy's assassination. Although Kennedy did increase U.S. covert operations and advisory roles in Southeast Asia, including the secret bombing of Laos and support for guerrilla operations, some historians believe he might have avoided a full-scale military intervention had he not been assassinated.