Every year the situation in Afghanistan is reassessed, and every year the conclusion is the same—mixed military progress, but otherwise, zilch. Romans would not have gone there, at least not on the terms that we are there.
The Roman empire was a success, for the Romans at any rate, because it was under their total control. When they moved into places like the Greek East, they were dealing with cultures that were largely urbanised. Administrative structures were in place to handle governance and taxation, and an élite ran the show. Romans could convince the élites it was to their advantage to be under light Roman control. But tribal northern Europe was a different kettle of dormice.
When the Romans moved into Britannia in AD 43, southern England had enough of a hierarchical structure to be controllable. But the further north they went, the more difficult it became. The problem was that territories requiring a constant military presence could never, by definition, be handed over to the locals to run. That meant they were ungovernable in the long term. In the 1st C AD the British governor Agricola did his best to make headway into Scotland from Rome’s furthest northern base in York, but could never get a grip on the tribes there. Shortage of manpower did not help either.
So the Romans gave up and built Hadrian’s Wall instead (AD 122), a Roman military zone, under army control, where civilian and other access was strictly forbidden, except at the controlled crossing-points. Romans were now able to supervise movements north and south of the Wall, prevent petty raiding and hinder large-scale attacks, and so encourage peaceful development of Britain right up to that frontier.
The central difference with the situation in Afghanistan is obvious. Far from taking the place over—not even building a Waziristan wall—we are working there only with Afghan consent. We are not, therefore, in control. So the question is: what is in it for Afghanistan? Do they really want what we want from our presence there? We shall find out only when we have left. It could be very cold comfort.