The United States deployed troops to Vietnam in the mid-20th century as part of their policy of containing the spread of communism. At the time, there was a strong fear among American policymakers that communism was spreading throughout Southeast Asia, and that if the South Vietnamese government were to fall to communist forces, it would trigger a domino effect in the region, leading to the spread of communism throughout Asia. Additionally, the United States government believed that by aiding the South Vietnamese government in its fight against communist guerrillas known as the Viet Cong, it could prevent the spread of communism and promote democracy and freedom in Vietnam. These beliefs led to the gradual escalation of the conflict, with the United States deploying more and more troops to Vietnam over time.
