Maybe you can answer a question. Did we have a treaty with South Viet Nam, like SEATO or something? If so, we were honor and duty bound to come to the defense of the south.
This is an example of the poor state of history teaching in this country. When Pres. Nixon signed the peace treaty with the North Vietnam delegation that led to the end of the war and the removal of the American forces he assured the South Vietnam people that, in the event North Vietnam invaded, the US would come to their aid and drive them out again. When the North invaded, the Democrat controlled Congress, with John Kerry's testimony in mind, did not authorize any funding for the rescue of South Vietnam. The result is the infamous bug-out of the Saigon embassy, the deaths of millions of Vietnamese, Cambodians, and Laotians, and thousands of "boat people" fleeing the region. This is the true legacy of John Kerry and the so-called "peace" movement.
"Did we have a treaty with South Viet Nam, like SEATO or something?"
Something like that, yes.
http://vietnam.vassar.edu/overview.html