Now will both London and Washington listen? For more than three decades there have been warnings — in books, articles, speeches, columns on this page — about over-dependence by the democracies on American military might as being the sure way to solve the world’s problems.

America as a continued partner and friend — yes. But as a boss-figure, policy-decider, direction-setter, unipolar superpower, to whose coat-tails nations must cling at all costs for their security, and much else — no. That era has passed. In a networked world, in a digitally revolutionized world, old relationships have long since changed.

The big battalions and the mightiest defense budgets no longer decide. The battlefield has largely shifted. The Afghan withdrawal is certainly a botched and tragic muddle, but the first strategic mistake was to believe that occupying armed forces, once they had completed their specific task — in this case, the hunting down of the mass-killer Osama bin Laden — could somehow stay on and change the national culture by their presence.