James Traub is a contributing writer for the New York Times Magazine and author of, most recently, The Freedom Agenda. "Terms of Engagement," his column for ForeignPolicy.com, runs weekly.

The almost decade-long American war in Afghanistan has now reached the beginning of the end. All hopes of anything like "victory" have long since vanished, but so have most fears that falling short of victory will jeopardize American national security. The essential remaining questions, then, are what they once were in Vietnam: How fast do we leave? And what do we leave behind? My impression, after a short trip to Afghanistan, is that the United States should leave faster than President Barack Obama appears to want to, but slowly enough to give the Afghans at least a chance to stave off total collapse.

You can certainly meet officials here who believe, as Simon Gass, NATO's new senior civilian representative, does, that "we can leave behind a stable platform" by the current 2014 target date for withdrawal. But a U.S. official with considerable experience in Afghanistan offered a much more tentative metaphor: "Can we thread the needle here by 2014?" he asked. "Yes, but it will take some luck." Pakistan would have to apply pressure to the sanctuaries where insurgents now shelter, the Afghan army would have to make major strides in professionalism, and "we're going to need more political will expressed by President [Hamid] Karzai."

"Any sign of that?" I asked...

"No," he said, citing the Afghan president's continuing protection of highly placed criminals and warlords and unwillingness to permit independent political institutions, including the parliament, to flourish.

So why bother at all? Why not crate everything up and leave as fast as possible? There are several answers to this question, some quite persuasive...