When future historians look back on President Joe Biden's legacy, one major part of it will be the end he has brought to American troops fighting in Afghanistan. Exactly how these future historians will deem it is still uncertain, at this point. It could go down as an absolute fiasco -- a textbook example of "how not to end a war." But if the rest of the airlift goes as smoothly as it seems to be running now, perhaps history's judges will be a little kinder to Biden. Again, this is still very much up in the air.

The White House is now claiming at least a limited amount of success for the airlift operation. What they have accomplished in a very short time is impressive indeed -- we are now airlifting out something like 20,000 people per day, which in and of itself is a logistical nightmare. These figures are updated constantly, and they now stand at over 80,000 people evacuated since August 14. That is indeed impressive, especially when you consider how slow the start of this process was. But will even 20,000 a day be enough?

One metric Biden will be judged on is whether every American who wants to leave will be able to get out by the time the airlift operation ends. That emphasis is there for a reason, because not every media outlet reports this correctly -- some merely say "every American." But there are American citizens in Afghanistan who do not actually want to leave right now, for various reasons. We can't very well force them to pack up and go. Today, estimates are that around 1,500 Americans who want to leave still remain in the country. That's down from over 10,000 (the first vague figure the administration gave, a few days back), so that's also a measure of the airlift's success so far.

To date, no American has died trying to get out. That's also an important milestone that could be upended by just one person getting shot at a Taliban checkpoint. So it will remain a tenuous thing until everyone with a U.S. passport who wants to leave has safely done so.

As for the Afghans who have helped us and our allies over the 20-year period of the war, most estimates put this number at around 300,000 people. And that's assumably not counting their families, so the successful evacuation of this group would wind up with much higher totals than that. Obviously, not every one of them is going to make it out of the country on the airlift. There are those who don't live anywhere near Kabul, for instance, who cannot physically get to the airfield in time. There are many who may not even qualify for a "Special Immigrant Visa" (those who only very peripherally helped the American war effort, or cannot actually prove on paper what they did, years and years later). Nobody really knows the scope of what it would take to airlift out everyone who helped our side -- and that's if they could make it to the airport in the first place. The Taliban are reportedly getting stricter and stricter about who gets let through their checkpoints, as they've already seen both a massive "brain drain" of talent as well as an exodus of money from their country. They're not happy about either one of these things, to put it mildly. And that's before even getting into the retribution/revenge factor.

Amazingly, the Taliban and the United States have been working together fairly well on this entire operation. This is galling to many Americans, but the fact of the matter is the Taliban won. They now control the country, and all the levers of power. The choice is to deal with them or somehow attempt to go it alone (which would be insane, since we are already reliant on them to pass Americans through their checkpoints).

This is a completely ad hoc collaborative effort, and a very temporary one as well. The Taliban have one major goal: getting all American troops out of their country for good. We have many goals, obviously, including the same one as the Taliban -- to get all our soldiers out, period. Currently, the Taliban have drawn a red-line date for when all the American soldiers must be gone by: August 31. President Biden is publicly supporting this deadline, even though it seems to many to be an impossible one if Biden also makes good on his promise to get everyone out who wants to (and is entitled to) leave. We are less than a week away from that goal. If we kept up the same pace as we have hit now, perhaps a grand total of 200,000 people might be airlifted out. But that's probably too optimistic, since the last few days will consist mainly of transporting all the soldiers out safely.

Biden has been giving all of this the best spin he can, touting the airlift itself (calling it akin to the Berlin Airlift) and trying to focus people on a much longer view than just what has happened over the last several weeks. Biden has also tried to gloss over the gross error in planning that led to the idea that the military should be evacuated first and then all the civilians afterwards, over the course of a few leisurely months (or perhaps even a year or two). This was some major-league hubris, obviously. But Biden hasn't really acknowledged the magnitude of this planning error yet. Incredibly, he asserts that the chaos was inevitable and would have happened even if the evacuation had started "a month ago." That is simply not believable, and Biden should soften his language considerably. If the airlift had begun a month ago, the hard cold fact is that the people fleeing would not have had to run the gauntlet of Taliban checkpoints, since back then the Taliban were nowhere near Kabul. Granted, Biden could be right that any exodus was going to be chaotic to some degree or another -- but there is chaos without the Taliban controlling the streets... and then there is the chaos we are seeing nightly on television. These are two wildly different scenarios, obviously. But Biden still speaks as if the two were somehow equivalent. This is a political error, since just about anyone can see the clear difference between the two.

The next two weeks are going to be crucial. Biden may be able to convince the Taliban to give us a very limited extension on that August 31 date, but probably not much longer than a few days to a week or two, at the absolute outside. As far as the Taliban are concerned, American military members were supposed to have all gone home this spring, on the original deadline Donald Trump negotiated. They've been pretty adamant so far about the end of the month being the ultimate deadline, so it's hard to see them giving in much at all. Biden has been publicly aiming for the same deadline, although he will admit there are contingency plans just in case.

My guess is the American public isn't going to measure this by the calendar, they're going to measure it by the actual results. If we get all Americans who wish to leave out safely, then nobody's really going to care what date we achieved it, to put this another way. If we get most of the interpreters and translators and other key Afghan personnel and their families out as well, then that will likely be judged a relative success (again, no matter when it happens).

If Biden falls short in any way, however, he's going to have to own it. He keeps echoing Harry Truman's "the buck stops here," and he will have to live up to those lofty words if anything goes wrong in a big way.

Biden's entire presidential legacy doesn't hang in the balance -- he will be judged on other accomplishments and failings as president. But the end of the Afghan war effort is sure to at least be a large part of his foreign policy legacy, and at this point it is impossible to tell how this legacy will be seen in the future. He's still got a chance to not have this chalked up as a monumental fiasco, but everything really has to go right for that to happen. We'll find out over the next two weeks whether he can pull it off or not.

-- Chris Weigant

Follow Chris on Twitter: @ChrisWeigant