Why was the Americans in the Vietnam war?

Answer 1

Following the Battle at Dien Bien Phu, Vietnam became North and South Vietnam. The non-communist South asked the U.S. for military and economic help to stop the North Vietnamese and the Viet Cong from trying to take over South Vietnam. The Eisenhower administration provided South Vietnam with money and advisers to help stop the threat of a North Vietnamese takeover. The United States also was pledged by treaty (SEATO) to aid the member nations in southeast Asia, if they were attacked by a foreign (communist) power. Following the Eisenhower and Kennedy administrations, President Lyndon B. Johnson also believed in containment and the domino theory. If one nation falls to communism, the next nation will fall, and the next, etc. It became the aim of the Johnson administration to prevent a communist takeover in Southeast Asia.
In August, 1964, President Johnson reported to the nation that American ships had been attacked by North Vietnam gunboats in the Gulf of Tonkin, in international waters. The Congress passed the Gulf of Tonkin Resolution giving the President the power to use whatever force necessary to protect our interests in the area. At the time, the truth was not reported.
<< Rather than being on a routine patrol Aug. 2, the US destroyer Maddox was actually engaged in aggressive intelligence-gathering maneuvers --- in sync with coordinated attacks on North Vietnam by the South Vietnamese navy and the Laotian air force.>> http://www.fair.org/index.php?page=2261
In February, 1965, the Viet Cong attacked an American military base near Pleiku. Using the Gulf of Tonkin Resolution, President Johnson sent in 3,500 Marines, the first official troops, to South Vietnam. By the end of the year, there were 200,000 US troops in Vietnam.