Why were we in Vietnam war?

Answer 1

The Vietnamese war was fought by America to hold the line against the spread of Communism; While North Vietnam was under communist rule and supported by China, South Vietnam was under the capitalist system. The US intervened because they believed that should Vietnam fall completely to communism other neighboring countries, (Such as Laos, Cambodia, and Thailand) would do the same, following the domino effect.

Answer 2

It was the easiest place to have a war: it was close to Communist China, which was good for re-supply. It was a north & south country, which gave it a good excuse for fighting a war, and it was bordered by other countries, which the communists knew the US would either have to involve them in the war, or face a losing proposition if they did decided to fight one there; and NOT involve those neutral countries (which the communists involved...but KNEW the US would not (officially). And they proved correct.

Answer 3

Communist aggression; part of the cold war.