Barack Obama is set to reject the advice of the Pentagon by announcing on Wednesday night the withdrawal of up to 30,000 troops from Afghanistan by November next year, in time for the US presidential election. The move comes despite warnings from his military commanders that recent security gains are fragile. They have been urging him to keep troop numbers high until 2013. The withdrawal has created deep divisions in Washington. The defence secretary, Robert Gates, argued for a modest reduction – at one point as low as 2,000 – citing the advice of US commanders in Afghanistan that they...