The commander of Canadian Forces in Kandahar in 2006, David Fraser, just said that it was a mistake to take down the Taliban. Wow. He argues that the alliance/coalition should have told the Taliban to step aside while US/UK/France/Canadian/etc forces hunted for Al Qaeda in Afghanistan.
How would that have worked? "Excuse me, I see a spot of AQ in Kandahar, don't mind us as we traipse through your heartland." Um, ok. Given that the Taliban's legitimacy was based on adherence to not just Islam of a particular kind but of Pashtunwali, which means taking care of those who one is hosting, it is hard to see the Taliban not minding the outsiders coming through the country.
Oh, and how would the US and others have planned ops in a Taliban-run Afghanistan while chasing AQ? Gambling that they would not be attacked by Taliban forces while chasing AQ? Sure.
I have been preaching humility here for some time--that intervention is hard precisely because it involves building on/trusting the locals to do some serious governance stuff. But the circumstances of 2001 were distinct from Iraq 2003 or Syria 2016. There are some original sins, but I am not sure that taking out the Taliban was one of them.
Original sin #1: Foisting on Afghanistan institutions that made little sense and did not build on years of study of building governance in ethnically divided society. Empowering a single president and making sure that all provincial and district leaders were more beholden to the dude in Kabul than to their own people? Not good.
Original sin #2: The US obsessing about Iraq, which created a security void in Afghanistan that ISAF only started filling in 2005 when it began to rotate out of Kabul and into the rest of the country. Once the Taliban was on the run, the US and its allies should have tried to do in 2002 what it did in 2009-2010--surge, provide some governance, start the training of the Afghan army and police as the clock had started on the patience of the democratic publics.
Original sin #3: Doing anything that caused the US/NATO/whoever effort to depend on Pakistan. Having no leverage on Pakistan and Pakistan having heaps of leverage was death to the mission.
Some of this is easy to say from the perspective of 2016, but sins 1 and 2 were pretty damned obvious way back when and there were people upset at them, as they foresaw the problems that these sins would create.
There is one other thing to consider before buying into Fraser's argument: the Taliban were awful, awful, awful--despite the violence of the past 15 years, Afghans are arguably better off. Infant mortality is down, there was little violence in the cities until recently, the economy grew, etc. Anyone buying into humanitarian norms such as responsibility to protect would find the idea of letting the Taliban stick around to be anathema.
But, Fraser is right about one thing--regime change is damned hard.
[and yes, there are sins that we and others committed before 9/11--ignoring Afghanistan after the Soviets left, the Soviets invading, etc, but this is focused on the post 9/11 sins]