Until the recent elections there under the aegis of the UN, I believed the Afghan war to be necessary, and one the US could not afford to leave. The dangers are clear. Letting Afghanistan revert to what it was before the 2001 invasion -- it is obvious that the Taliban will come back to power should UN forces leave -- allows it to become again a festering would, a rebuke to all decent and good countries. It would once again a haven for training terrorists.
The greater danger is nuclear-armed Pakistan, which is struggling mightily as it is against a resurgent Taliban within its borders. Pakistan is also losing the influence it once held with its Talib clients in Afghanistan. Should Afghanistan revert to Taliban control, I fear that Pakistan would not be able to resist for long; the government would fall, and suddenly the nukes would be much looser than they are now. It's not far-fetched to fear that certain ISI agents with lingering ties to the Taliban could decide to cast their lot in with the terrorist group, bringing nuclear weapons with them. The prospects then are clear.
But I fear the Afghan situation may no longer be tenable. So long as America was fighting in support of democracy, there was a clear moral good. That is no longer the case, as it has become obvious that the past elections witnessed major fraud condoned by the same organization that was meant to monitor and verify the situation. America's top diplomat on the mission was fired for not going along with the corruption:
Given our mandate to support “free, fair, and transparent” elections, I felt UNAMA could not overlook the fraud without compromising our neutrality and becoming complicit in a cover-up. For a long time after the elections, Kai denied that significant fraud had taken place, even going to the extreme of ordering UN staff not to discuss the matter. And, at critical stages in the process, he blocked me and other UNAMA professional staff from taking effective action that might have limited the fraud or enabled the Afghan electoral institutions to address it more effectively.Given our current difficulties in winning the populace to our side, the hurdle has just been set much higher; we should also expect a certain amount of disaffection to spill over into outright support for our enemies. There is no way, now, of reversing the situation in Afghanistan. To be clear: if we stay, we will be fighting in support of a corrupt, illegitimate regime.
I don't have the answer; I don't know where the scale tips. But the tipping point is very, very much closer now.