you go to war with the allies you have, not the ones you wish for, to paraphrase Donald Rumsfeld. President Barack Obama’s war on the Islamic State of Iraq and the Levant (Isis) is a good example. His Middle East coalition comprises five autocracies, four of which are monarchies. To one degree or another, each represses dissent. Each, indirectly or inadvertently, has helped spawn groups such as Isis, Khorasan, Jabhat al-Nusra and, of course, al-Qaeda. Each will reap longer-term profit from assisting the US in its hour of emergency. Things have worked this way in the Middle East for decades. At a moment like this, it would be naive to expect Mr Obama to change that.

At the heart of this Faustian pact is Saudi Arabia. Americans have not forgotten that 19 of the 20 hijackers on September 11 2001 were Saudi citizens. Nor have they forgotten the mistaken 2003 US pivot to Iraq. Today, much like the day the Twin Towers fell, the most direct global threat to the US comes from Islamist terrorism – the Sunni variety, to be precise. None of the terrorist plots in the US and Europe since 9/11 have been devised by Shia groups. Yet the one ally that is off-limits to Mr Obama is Iran – Saudi Arabia’s Shia counterpart and its greatest foe.

Given his constraints, Mr Obama has cobbled together the best alliance of expediency he can find. But his mission targets a symptom rather than the causes of Salafi extremism. The trade-off has deep precedent. In the 1980s the US joined Pakistan, the Saudis and other Gulf states to back the mujahideen against the Soviet Union in Afghanistan. That war provided the crucible for the Taliban and al-Qaeda, both of which are resurgent today. The US also backed Saddam Hussein’s Iraq in its long and bloody war with Iran. That did not work out too well either. In the 2000s the US diverted itself into invading Iraq – no friend of al-Qaeda, but an enemy of the Gulf states. In most of these cases, a US-led war succeeded in the short term but sowed the seeds for greater problems later on. Why should the fight against Isis be any different?