Paul Pillar thinks an arbitrary deadline for withdrawal from Afghanistan is unavoidable:

President Obama’s announcement of a drawing down of remaining U.S. troops in Afghanistan over the next two years, to what will be an ordinary embassy presence by the end of 2016, sounds like it involves an arbitrary deadline that will enable him to say when he leaves office that he got the United States out of its foreign wars. Of course it does. And we should not fret about that. If we can’t find an obvious off-ramp, the end of a presidential term is as good a ramp to use as any other. Give Mr. Obama’s successor more of a clean foreign policy slate, all the better to concentrate on other matters.

The truth is that there is no deadline that would not be arbitrary in one way or another. There will always be excuses to keep U.S. forces in the country even longer, and there will be a dedicated group of politicians and pundits that will never accept that it is time for U.S. forces to leave. For these people, any deadline is too soon, because most of them don’t really think that the U.S. should withdraw in the first place. If there is anything to object to in the president’s decision, it is that he offered a pointless sop to his hawkish critics. He has chosen to keep a residual force in Afghanistan beyond the end of this year for no real purpose except to be able to say that there will briefly be a few thousand troops staying behind for a little while longer. Naturally, hawkish critics have not been placated, and have just found something else to complaint about. The only problem with these deadlines is that they can always be revised and pushed back, which always leaves open the possibility that the promised withdrawal never comes.