Some time in the next two weeks, Mr Obama is likely to bring months of agonised deliberation to a close when he decides how many more troops to send to Afghanistan. The number, which could be as high as the 40,000 recommended by Stanley McChrystal, the general in charge, will be analysed minutely for what it can achieve on the ground in Afghanistan.

The decision, much like the one by Lyndon Johnson to step up involvement in Indochina, could prove to be the most important Mr Obama takes in office. It presents America’s most liberal president in a generation with a classic dilemma between guns and butter that is only likely to deepen, whatever choice he makes.