Don't forget that South Vietnam was holding its own until the DEMOCRATS cut off the $$$.
And that doesn't even mention the fact that we had to fight that war with our hands tied behind our back. If the pukes in Washington had gotten out of the way and let warfighters take care of business, WE would have won inside of six months!
Haiphong Harbor was off limits for bomb runs, but most everything that came down to Ho Chi Minh trail sat on the docks there, first.
Despite being hobbled by the Pentagon and politicians, our troops won every major engagement. The Media didn't help, presenting Tet as some sort of defeat, when every provincial capital was invaded during a cease fire, simultaneously, and all were retaken (with the exception of Hue, because of R.O.E.) in short order, effectively eliminating the Viet Cong as a fighting force. Subsequent engagements were fought against mostly NVA regulars.
Crap that went on there still angers me, and I wasn't in the service, though many of my friends were, some in country.