One immutable law of insurgency warfare is that, while conventional armies need to win, insurgents need only to avoid losing. The disagreeable truth is that, though we are not losing the war in Afghanistan, we are not winning. Neither, looking at the current situation, are we likely to.
This means a fairly stark choice. We can struggle on, as in Iraq, losing men and money for years until an Afghan version of the James Baker report tells us to change tack - or we change tack now.