How did “Domino Theory” play into the Vietnam War?

The domino theory was the basis for the United States strategy of containment, and the reason for entering the Vietnam War. ... The domino theory basically stated if one new countrywent communist in Asia then it would begin a chain reaction that would cause several more Southeast Asian countries becoming communist.

Explanation: hope this helps. It has a little information that I learned about it.

it was on the rise and doing very well and would continue to do well until the great depression from 1929-1939