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It has become a pub bore's cliché to argue that we will never prevail in Afghanistan because no foreign power ever has: not even the Russians, whose nine-year occupation cost the lives of 14,000 of their soldiers and 35,500 wounded, and which ended in humiliating retreat in 1989. Those Cassandras irritate Western leaders, whose response is to insist that it is different this time. "We are not an occupying army," Gordon Brown told the BBC on Friday. "It's not like previous interventions.... We are actually creating the conditions by which the Afghans themselves, and not an occupying army, can run their own affairs."

Ture, history does not repeat itself in every detail. Nato, for instance, would never adopt the scorched earth tactics of the Soviet Union, which led to the deaths...