Jon,

History shows that a successful exit from Afghanistan depends on bribery, negotiation, skill and acceptance by those Afghans who can obstruct. Their obstruction can take many forms, not always violent.

A sketchy account of one exit, long ago is:http://en.wikipedia.org/wiki/Battle_...ahar#Aftermath

A more detailed history of exiting Afghanistan is being prepared by a British historian, almost "just in time".

To date I have very strong doubts politicians know what needs to be done to reduce our presence, if not exit. Phrases like "See it through" and we "Need a narrative to explain why we're leaving" do not help.