Vietnam was a struggle which, in all honesty, the United States should never have been involved in. North Vietnam was battling for ownership of South Vietnam, so that they would be a unified communist nation. To prevent the domino effect and the further spread of communism, the U.S. held on to the Truman Doctrine and stood behind the South Vietnamese leader, Diem. Kennedy and Diem were both killed in 1963 and 1964. Johnson took control of the situation by increasing the amount of money and manpower put into Vietnam. Congress passed the Gulf of Tonkin Resolution, giving the president full military power. After Johnson dramatically escalated the amount of soldiers in Vietnam,