Our objective was to prevent the North Vietnamese from taking over the South. We had it won by making them militarily incapable of doing so. The Viet Cong was useless, the NVA was defeated every time they came out, and Giap would later say that if it weren't for the rebirth of the antiwar movement in Kerry's era, they would have stopped trying to take the South.
Vietnamization was proceeding well, and we were on track to have a relationship with the South like the one we already had with the ROK--You guys are your own show, but we're ready to provide massive combat power to defend you if your criminal neighbor invades. But then something happened...and that something is the answer to the question in my last post to you. So answer that and get back to me.
Just think about that for a moment, and imagine what it would be like for the U.S. to be involved in major combat operations from 1965 through 2000 -- which would have included the administrations of seven U.S. presidents.