The Washington Post reports that there's already disagreement between American and Afghan officials about exactly what "withdrawal" means:
Top Afghan officials said Obama’s pledge last week to remove U.S. troops from Afghan villages should apply to Special Operations forces charged with training the Afghan Local Police. But U.S. officials said they assumed that the policy would apply only to traditional military operations and would include an exemption for the police trainers, whose mission they see as critical to security throughout Afghanistan.
The dispute underscored just how difficult negotiations over a long-term security partnership could be during the next year. The disagreement, like others before it, centers on the fundamental question of what will keep Afghans safe: U.S. officials say the local police program thwarts insurgents, but Karzai insists that it invites attacks.
I know it's easy to get too simplistic about this stuff, but in this case I think simplistic is best. This kind of mission just flatly can't work if the host nation isn't cooperative. So it really doesn't matter how critical Americans think the training program is. If Afghan leaders are opposed to it, then it's time to stop. It's not worth risking a single American life for a program that has no chance of producing long-term results.
The U.S. mission in Afghanistan has failed. Maybe that's because of poor planning, or maybe it never had a chance of working regardless. At this point it no longer matters except as grist for lessons learned. It's time to get out.