Involvement in South Vietnam began in 1953 under the Eisenhower administration with 900 military advisors and US Air Force pilots flying for CAT (Air America). When President Kennedy was elected in November of 1960, Ike advised him that Vietnam and Southeast Asia were the critical area and needed a high priority for military assistance.
US Ambassadors did not believe Diem would accomplish US goals in Vietnam.
Eisenhower.
President obama
Lyndon Johnson.
When Nixon ordered "military trainers" to Vietnam, the U.S. then started to become actively involved in Vietnam combat.
Lyndon Johnson.
Lyndon Johnson was the President of the US during the Vietnam War from the assassination of John Kennedy until the election of Richard Nixon.
That's hard to answer. Both Lyndon Johnson and Richard Nixon were very involved in Vietnam in somewhat different ways.
After a series of South Vietnamese government leadership changes, following the assassination of President Diem, President Nguyen Van Thieu became the leader of South Vietnam.
Just as responsible as Eisenhower before him, and LBJ after him. They all played their part.
No US president fought in the Vietnam War. Eisenhower and Kennedy were the president when the US first became involved. Johnson and Nixon were the president when the serious fighting took place.
"Escalation" .