According to the brass & politicians it was a war of attrition. In theory when we killed enough of them they would give up. However, the North was willing to fight to the last man or woman or child. We used every weapon in our arsenal to kill the communists (except biologic & nuclear…even at that we used Agent Orange & other chemicals at hand).
The American public lost stomach in this type of war. I do believe that at some point the average American grunt would have rebelled in killing ever younger/older enemy troops even had we been allowed to invade the North. There were well over a million Vietnamese (N&S) who died in during the war. That does not include those in Laos, Cambodia or the many lingering deaths from Agent Orange, unexploded ordinance, etc.
In WW II German leaders divided their homeland and conquered lands in terms of “good and bad” people. The German policy was to kill-out all the bad folks (a few were sent to “re-education” camps). Pretty much what we did in Vietnam. We never envisaged our war in those terms, but that was the path on which our leadership placed us.
Before we condemn that leadership recall the era in which they/we existed then: In the ’50’s the popular slogan was “The only good Red is a Dead Red!” History had recently proved that theorem when the Russian purge resulted in tens of millions dead and in China literally hundreds of millions perished. There was nothing even remotely good about the Red Peril. We went into Vietnam dedicated to blunt the spreading evil of Communist domination.
Hindsight is excellent. Too bad we did not have it then. In the long term, Communism was unable to further spread it’s heinous body and then fell under it’s own weight…Thank God!