After the assassination of John F. Kennedy, his deputy, Lyndon B. Johnson became the new president of the United States. Johnson was a strong supporter of the Domino Theory and believed that the prevention of an National Liberation Front victory in South Vietnam was vital to the defence of the United States: "If we quit Vietnam, tomorrow we'll be fighting in Hawaii and next week we'll have to fight in San Francisco."
Johnson, like Kennedy before him, came under pressure from his military advisers to take more 'forceful' action against North Vietnam and the NLF. The Joint Chiefs of Staff advised Johnson to send United States combat troops to South Vietnam. The overthrow of President Ngo Dinh Diem had not resulted in preventing the growth of the NLF. The new leader of South Vietnam, General Khanh, was doubtful that his own army was strong enough to prevent a communist victory.
Johnson told his Joint Chiefs of Staff that he would do all that was necessary to prevent the NLF winning in South Vietnam but was unwilling to take unpopular measures like sending troops to tight in a foreign war, until after the 1964 Presidential Elections. Just let me get elected," he told his military advisers, "and then you can have your war."