A friend posted this on Facebook today.
From the Atlantic:
The Doves Were Right. I Was Wrong.
Americans like me ignored—or scorned—protesters who warned of an endless quagmire in Afghanistan. Next time, we should listen to the critics.

First thought: "Finally, a prominent supporter of the war is admitting his mistake."
But actually, a close reading of the article reveals the author was just 21 years old at the beginning of the Afghanistan war.  Two years younger than myself.  Now he's a middle-aged columnist.

But then, that's how it goes.  The Afghanistan War is America's longest war ever.  We've all become old men while the Afghanistan War has been going on.  There are people who will be voting in the next election who weren't even born yet when the Afghanistan War started.

The Atlantic article, and The Washington Post article it references, are both must reads for finding out just how much this war has cost America, and what a complete disaster it has been from the beginning to now.

The obvious comparison is, of course, the Vietnam War.
People often say America lost the Vietnam War, but America never really lost.  We were the most powerful military in the world. There's no way we could ever have been defeated by a third-world nation of rice farmers.

But, we could never have won either.  There was no way we could invade a country we didn't understand, re-structure it so that it was just the way we liked it, and then leave and expect everything to stay like we had left it.  The moment we left Vietnam, the Vietnamese would just go back to structuring their society like they wanted.
We never really "lost" the war.  We could have stayed in Vietnam forever if we had wanted to.  But the one thing we couldn't do is leave and expect things to stay the way we had left them.

In the same way, we can stay in Afghanistan forever if we want to.  But there's no way we can ever win this war.