What was the primary reason for the U.S. involvement in the Vietnam War?

The primary reason for U.S. involvement in the Vietnam War was to prevent the spread of communism. This objective stemmed from the broader context of the Cold War, where the United States adopted a containment policy aimed at stopping the influence of communist regimes worldwide. The belief was that if one country fell to communism, neighboring countries would follow, a concept known as the "domino theory."

In Vietnam, the U.S. was concerned about the rise of the communist government in North Vietnam and its support for Viet Cong insurgents in the South. The commitment to preventing communism not only drove military engagement but also influenced political and economic alliances in the region. As a result, the U.S. escalated its presence in Vietnam, believing that any retreat would jeopardize not only Vietnam's future but also the stability of Southeast Asia and, potentially, beyond. This reasoning reflected the U.S. perspective during the Cold War, where ideological conflicts often determined foreign policy decisions.