It is hard to believe that only this time last year President Barack Obama addressed the American public about the need to punish Syria for crossing his “red line” on chemical weapons. Events have turned almost full circle, as happens in the Middle East. Today Mr Obama unveils plans for “systematically degrading” the Syrian regime’s deadliest opponent – the Islamic State in Iraq and Syria.

Everybody has been caught unawares by the frightening speed of events in the region. Last month Mr Obama admitted he had not yet devised a strategy to contain Isis, let alone defeat it. It was a costly slip of the tongue. Today he must convince America’s allies, particularly in the Middle East, that he has a strategy which is more than simply reactive.

His first goal must be to win round America’s regional allies. Much has been made of declining US power, not least in the Middle East where Washington can no longer exert a hegemonic role. Whether such fears are overstated, Mr Obama can only be effective as leader of a coalition, rather than a lone ranger. He made a good start this week by helping to broker a new Iraqi government under Haider Al-Abadi. It is critical he maintains pressure on Baghdad to bring Sunni moderates on board. Without their support, it will be impossible to halt Isis’s murderous offensive. That will mean defanging the Shia militias and going beyond the usual sectarian job-sharing formulas to stitch together a genuinely inclusive government. Isis has been fuelled by Sunni alienation. It must be redressed.