Who was US President at the beginning of the Vietnam War?
Kennedy Since there is no clear absolute date for the beginning of the war, we could say President Eisenhower or Kennedy. There were advisors there during the Eisenhower presidency (1953-1961) but combat troops were sent in during the Kennedy/Johnson administrations (1961-1969).
This question requires a subjective answer. This is so, because there was no "declaration of war" issued by the US concerning the war in Vietnam. Based on opinion, US President Johnson becomes the answer. The reason for this is the Gulf of Tonkin Resolution. This incident brought on the War Powers Act and placed President Johnson as the "leader" at the "beginning" of the Vietnam War.