How did the “domino theory” lead the United States to send troops to Vietnam

The United States feared that if communism was successful on Vietnam, the rest of the countries that border it would soon turn into communism and those other countries that border that new communist country would also be converted to communism and so on. This is called the "domino theory" and made the United States to send troops to prevent the theory from happening.

he didn't think it was ethically wrong. he thought it was not going to work and it was not going to be of any assistance. he wrote about that in his memoirs.

b. andrew