Why did the United States enter the Vietnam War?

The primary reason for the United States' entry into the Vietnam War was to stop the spread of communism. This decision was rooted in the broader context of the Cold War, during which the U.S. aimed to contain communism and prevent it from expanding into Southeast Asia and beyond. The belief was that if one country in a region fell to communism, neighboring countries would also follow, a theory known as the "domino effect."

At the time, the U.S. government viewed the conflict in Vietnam as a critical front in the fight against communist ideology, which they feared could undermine democratic governments worldwide. This overarching objective of containing communism was a driving force behind U.S. military and economic support for South Vietnam, as well as the eventual deployment of combat troops.

In contrast, while promoting democracy is a potential goal of U.S. foreign policy, it was not the primary reason cited for involvement in Vietnam. Support for French colonial efforts was a factor in the early stages of the conflict, but it was not the main justification for the war as it escalated. Although protecting American citizens is always a concern in foreign policy decisions, the primary stated motive for the Vietnam War was the broader objective of preventing the spread of communism.