History of Vietnam. Several American Presidents are mentioned in this essay dealing with Vietnamese history. In this case, the focus is on the Vietnam War.
From the site:
In December 1961, at the request of South Vietnamese President Ngo Dinh Diem, President Kennedy sent U.S. military advisers to South Vietnam to help the government there deal with the Viet Cong campaign. In the wake of escalating political turmoil in the south after a 1963 generals' coup against President Diem, the United States increased its military support for South Vietnam. In March 1965, President Johnson sent the first U.S. combat forces to Vietnam. The American military role peaked in 1969 with an in-country force of 534,000.