Question

how was the \domino theory\ applied to the vietnam war?

the united states quickly withdrew its troops from vietnam after a series
of military losses that made it apparent that victory in the conflict was
unachievable.
the united states believed that by winning the conflict and installing a
democratic government in vietnam, other nations would adopt democratic
reforms.
the united states became involved in the conflict in vietnam because us
leaders feared that if south vietnam fell to communism, other countries would
soon follow.
the united states entered into a series of military alliances with major world
powers prior to the conflict to provide them with the support needed in the
war.

Explanation:

The domino theory posited that if one country in a region fell to communism, neighboring countries would sequentially fall to communism, like dominoes toppling. This was the core rationale for U.S. intervention in the Vietnam War, as policymakers feared the spread of communism across Southeast Asia.

Answer:

C. The United States became involved in the conflict in Vietnam because US leaders feared that if South Vietnam fell to communism, other countries would soon follow.