Which ideology motivated the US involvement in Vietnam?

The United States' involvement in Vietnam was primarily motivated by the ideology of communism. This was a pivotal period during the Cold War when the U.S. government sought to contain the spread of communism, which they perceived as a significant threat to democracy and capitalism. The fear of a "domino effect"—whereby one country falling to communism would lead to neighboring countries following suit—was a driving force behind U.S. foreign policy decisions in Southeast Asia.

The ideological battle against communism was further justified by the belief that it was essential to support governments resisting communist insurgencies to protect democratic values. This resulted in significant military and economic support for South Vietnam in its fight against the communist North Vietnamese forces and the Viet Cong. The commitment to combating communism led to the escalation of U.S. troops in Vietnam and deepened American involvement in the conflict throughout the 1960s.