Stephen Walt provides by far the best summary I’ve read of events in Afghanistan since 2001:
[…] About eight years ago a small group of anti-American criminals hijacked four airplanes and flew three of them into buildings in the United States. The ringleaders of the plot were in Afghanistan, and the Afghan government (at that time under Taliban control) refused to give them up. So the United States invaded to overthrow the Taliban and capture the al Qaeda leadership. Unfortunately, we failed to get the latter, and we bungled the subsequent reconstruction effort by going into Iraq, thereby enabling the Taliban to make a comeback. So now we’re escalating there once more, in a potentially open-ended effort to build a functioning and legitimate Afghan state. And now that means fixing their prison system too. How does one say “mission creep” in Pashto?