Admittedly, our troop presence has declined substantially since the Obama-era surge of troops and the much smaller early-Trump-administration troop increase. So it’s possible that in a Trump second term or a Bernie Sanders presidency it will finally trace a slow descent to zero — with or without a deal of some sort with the Taliban — and after 20 years or so we’ll finally discover that even endless wars can end.

But it’s also possible that in cutting troop numbers the Pentagon is groping toward sustainability rather than an endpoint — toward some figure that’s deemed sufficient to manage stalemate, to preserve certain American objectives and prevent the embarrassment of real defeat.

In that case, despite the similar pattern of deception and denial, Afghanistan could represent something very different from the Vietnam experience. Vietnam proved that despite a certain amount of patriotic naïveté, Americans ultimately wouldn’t put up with a seemingly unwinnable war founded on lies and self-delusion. But Afghanistan may yet prove that given an all-volunteer military, the right amount of cynical detachment at home and a low enough casualty rate in the theater itself, Americans will accept a war where there is no prospect for victory, and no clear objective save the permanent postponement of defeat. More even than our Indochina debacle, it could bury George Patton’s dictum about our addiction to victory, our contempt for defeat, by proving that 21st-century Americans have learned to swallow stalemate.