Know your enemy is the first rule of strategy, yet it is one that Americans have found difficult to follow over the past decade. Not knowing the enemy has unfortunate consequences: it can lead to being surprised by unanticipated strengths while failing to exploit neglected weaknesses.

Recent US experience bears this out. Overthrowing Saddam Hussein’s regime was said to be critical to the war on terror, yet Iraq’s links with al-Qaeda were minor. US forces were caught out by the intensity and multi-faceted character of the insurgency. When Iran was designated a member of the “axis of evil” in 2002 this was something of an afterthought, as Tehran and Washington had co-operated in Afghanistan and could have done so over Iraq. Since then the Bush administration has scrambled for a credible policy to deal with this “evil” and has appeared nonplussed as Iran emerged as the main beneficiary of its regional policies. There has also been uncertainty over the unity of the Taliban and whether it should be treated as indistinguishable from al-Qaeda. Until recently all Palestinian groups were treated as being as bad as each other, before the realisation that the Islamist Hamas was becoming more dangerous than the secular Fatah.