How did Cold War fears influence U.S. involvement in Vietnam?

Cold War fears were the primary driver of U.S. involvement in the Vietnam War, rooted in the strategic imperative to contain the spread of communism globally.12

The most influential concept guiding this policy was the domino theory, which posited that the fall of one noncommunist state to communism would inevitably trigger the collapse of its neighbors. This theory magnified the perceived importance of Vietnam, leading U.S. policymakers to view the conflict as a critical test of American credibility and resolve against the Soviet Union and China.31

Following the Truman Doctrine, which established the U.S. role in protecting "free peoples" from totalitarian regimes, the United States felt compelled to act as a global protector. Washington feared that allowing a "war of national liberation" to succeed would signal weakness, prompting the U.S. to escalate its involvement from providing aid to deploying combat units to prevent the loss of prestige and the potential expansion of communist influence in Southeast Asia.14