Why did the US become involved in military conflict with Vietnam?

There were many stages of escalation from countries accross the globe, leading up to US military involvement in Vietnam. The events began with the French, who had returned to Vietnam to claim it for their empire after World War 2. It wasn't expected that this would take as long as it did. Incredibly the French were defeated by Ho Chi Mihn's Vietcong army at Dien Bien Phu. The Vietcong sought to promote communism in Vietnam. Communism …

…Vietnam. However, it is the belief of most historians that the Tonkin Incident was merely a scaled-up exaggerated cover for what was a much smaller incident involving many fewer people. This was bought as an excuse by most of the population and war seemed justified. Whatever truth lies behind the Tonkin Incident , it was in the end huge American mistake, which cost America $120bn, many lives and it appearance to the Communist world at large.