How was the conflict in Vietnam related to America's involvement in the Cold War?

The Vietnam War was a long, costly and divisive conflict that pitted the communist government of North Vietnam against South Vietnam and its principal ally, the United States. The conflict was intensified by the ongoing Cold War between the United States and the Soviet Union.

Because as most people know the north was communist while the south was a democracy and reason why Vietnam was because the north was a "threat"to the u. s. a's ideals