President Johnson escalated American involvement in the Vietnam War. In 1964, Congress passed the Gulf of Tonkin Resolution, which granted Johnson the power to use military force in Southeast Asia without having to ask for an official declaration of war.Johnson was committed to containment policy that called upon the U.S. to block Communist expansion of the sort that was taking place in Vietnam, but he lacked Kennedy's knowledge and enthusiasm for foreign policy, and prioritized domestic reforms over major initiatives in foreign affairs.The USA became involved in Vietnam because it feared the spread of communism. The USA were unable to defeat the Vietcong and were met with growing opposition to the war back home