The language used by Cameron in his TV interview in the US was no doubt designed for the local audience but it makes little sense. It is not possible to destroy IS any more than it is possible to destroy Christianity. What can be done is to contain it so that gradually it withers into a more amenable structure, concerned with its own survival and less focussed on threatening the world beyond its borders. It has redrawn the Sykes Picot map and and much of that may be beyond recall, but the regional mayhem needs to reduce. Armed force can help containment to give space for a political solution, but it cannot produce a solution on its own. We have learned that lesson and have had to do so several times. Now that we are working more closely with Shia Iran the prospects look more favourable.
There is absolutely no point in extending some random bombing campaign without it being backed by a full strategic overview, a clear set of objectives and an exemplary tactical plan, finished off with a clear exit mission. None of this exists in the minds of any of the politicians and in very few of the military. The assertion by the former head of the Army on TV that we should go onto a ‘war footing’ is just silly. We have had enough of these wars that go nowhere. Before the military gives advice to the government it will have to get real.