We invaded Afghanistan to capture or kill Osama Bin Laden and to end the Taliban government which sheltered him. At long last, both of those missions are accomplished.
That means we have achieved what we set out to do. Another word for that is victory.
Once you win, you go home. It really is that simple.
Our presence in Afghanistan is not free in any sense of the word. It imposes costs on the United States which are not only financial but political (in terms of our freedom of action in Central Asia, our relations with our NATO allies and, perhaps most importantly, our relations with Pakistan) and military (in terms of casualties and tying up a portion of our forces).
One key question to ask about a military commitment is: What are our victory conditions and when do we think we are going to achieve them? In evaluating arguments for remaining in Afghanistan, we should think about what those arguments mean for the answer to this question.
Arguments for staying in Afghanistan boil down to the following:
1. If we depart Afghanistan the Taliban will return to power. This is likely to be true. And it is not likely to be good for the people of Afghanistan. It is not clear, however, that it matters to America. While the Taliban sheltered Bin Laden after 9/11, they did not attack the United States, and, it is unlikely that they would choose to do so after an American withdrawal from Afghanistan. Other than preventing an attack on America, it is not clear that America has a strategic interest in Afghanistan sufficient to warrant a continued significant military presence.
The other half of the equation is that after ten years we have not managed to build a government popular and capable enough to keep control of the country nor have we eliminated the Taliban as an operational military force. Also, unfortunately, it does not seem that we are making significant progress toward doing so, nor do we appear to have a plan for doing so that seems likely to work.
Thus, this argument for remaining in Afghanistan would seem not to be a strong one, as it implies a long term commitment for very little reward.
2. Better to fight the terrorists over there than over here. The argument is that by killing terrorists in Afghanistan and Pakistan and disrupting their training and recruitment we prevent them from attacking America. This is probably the strongest argument for remaining in Afghanistan.
It is possible and even likely that our actions in Afghanistan and Pakistan have foiled or prevented terrorist plots. It is also possible and even likely that enhanced security coupled with Saudi Arabia's crackdown on Al-Qaeda for its own reasons has reduced Al-Qaeda's ability to carry such plots out. Certainly, since we have been in Afghanistan there have not been any bombings of ships such as the Cole or embassies such as the American embassy in Kenya. On the other hand, there have still been major Al-Qaeda terrorist attacks including the Madrid bombings in 2004.
Ultimately, this comes down to a cost benefit equation which is insoluble. I think it is likely that other changes in the world since 2001, including lower Saudi tolerance for Islamic fundamentalism, elimination of a large American military presence in Saudi Arabia, revolutions against dictatorial Arab regimes which have been at least partially supported by America and increased security and intelligence efforts mean that on balance it is not worth the expenditure of blood and treasure to remain in Afghanistan to provide an extra, unquantifiable, measure of safety.
3. We have a strategic interest in being able to intervene in Iran and/or Pakistan. We do have such an interest. However, our interest in intervening in Iran is limited, not really in the area bordering Afghanistan and sufficiently remote as not to provide a basis for our continued presence in Afghanistan. (As evidence, note that this would have provided a stronger basis for remaining in Iraq.)
Pakistan is more complicated. In particular, it is unclear whether our presence in Afghanistan is destabilizing Pakistan and it is unclear whether we could intervene effectively in Pakistan in any case. This, too, seems like too weak a reason to justify our continued military presence in Afghanistan.
I strongly supported our actions against Afghanistan in 2001. I continue to think those actions were correct. However, the reasons which justified those actions no longer exist.
The bottom line is that if it is not time to leave Afghanistan now, it is not clear when that time will come. And it is likely not in America's interest to be in Afghanistan, at war, indefinitely.