Understandably, and commendably, US president Mr Trump wants his troops out of Afghanistan and back home before he runs for a second term next year. His Mexican Wall has not been built; North Korea is still a potential nuclear power; he has not succeeded in repatriating jobs; his promise to cut the US trade deficit has been broken — it’s at a record high; federal debt has soared; and the Washington swamp, far from being drained, has been replenished. Ending an 18-year-long war that has been so costly in blood and treasure, 220,000 lives and €875bn, would be a notable tick in the credit column.