The Atlantic's website has a kind of review essay by Robert Kaplan about the "forgotten" Vietnam literature that provides a kind of user's guide to the revisionist accounts of the war that the president has decided to endorse. To me, the noteworthy thing about this case is how hollow it is even on its own terms. For contemporary political purposes, here's the key point:
While historians cite 1968 as a turning point because of the home front's reaction to the Tet offensive, the My Lai massacre, and the protests at the Democratic party convention in Chicago, on the ground in Vietnam, 1968 marked a different trend: William Westmoreland was replaced by Creighton Abrams, population security rather than enemy body counts became the measure of merit, "clear and hold" territory replaced the dictum of "search and destroy," and building up the South Vietnamese Army became the top priority. "There came a time when the war was won," even if the "fighting wasn't over," writes Lewis Sorley, a West Point graduate and career Army officer, in A Better War: The Unexamined Victories and Final Tragedy of America's Last Years in Vietnam (1999). By the end of 1972, Sorley goes on, one could travel almost anywhere in South Vietnam in relative security, even as American ground forces were almost gone. [...] Sorley told me he isn't sure what would have happened had Congress not cut off aid to South Vietnam at about the time the ground situation was at its most hopeful. He felt that a respectable case might be made that it would have survived.
The question naturally arises that even if one accepts all of this, what would the point have been? Propping up the South Vietnamese government was an expensive and diplomatically costly proposition. The initial strategic rational for propping up the South Vietnamese government was that preventing South Vietnam from going Communist was necessary to prevent the triumph of Communism worldwide. In retrospect, however, while "a respectable case might be made" that South Vietnam could have been saved, we know conclusively that the strategic case in favor of saving it was mistaken.
Recently, an indefinite military commitment to South Vietnam has been repackaged as some kind of humanitarian gesture, but that boat won't float. The Saigon regime was a dictatorship like the northern one, and Abrams-era US military actions like the Christmas Bombings killed thousands of people. Insofar as the point of a military activity is to accomplish something worthwhile at some kind of reasonable cost, Abrams/Kissinger/Nixon never did anything of the sort. Now, it's not Creighton Abrams' fault that there was no good reason to expend vast resources propping up the shaky South Vietnamese government indefinitely, but it's still the case that whatever tactical accomplishments the forces under his command may or may not have achieved that nothing he did actually vindicates the political agenda of indefinitely continuing the war.