In case you haven't noticed, the "debate" about Afghanistan going on inside the White House (thanks for the transparency) has already been decided, and the answer is: we're staying. The remaining question being considered is: how many troops? The question not being considered, if leaks are any indication, is why?
If there's any consistency to the foreign-policy mistakes of America in the post-World War Two era, it's the saga of brilliant men deciding upon wars in countries they barely understand, countries whose history they ignore--at our peril. That was the story of Vietnam, of Iraq, and it's now being repeated. It's also the story of a policy becoming hostage to notions of our "credibility" as a world power, as if being trapped in a debilitating struggle with enemies who aren't leaving (and who know we are) is good for the ol' image.
But, and I'm anticipating two-thirds of your comments, I'm "just" a funny person. You bet. That's why I pay attention to the people who know what they're talking about on this issue, and here's one of them--Matthew Hoh, who had the guts Colin Powell wishes he'd had, who resigned his State Department job rather than continue to promote a failing, misguided, doomed policy. Read Hoh's online chat. He's not kidding.