The battle raging in al-Qusair, about 15km east of Lebanon’s northern border, looks ominously like a turning point in Syria’s civil war. If the Assad regime can recapture this strategic corridor from the rebels, it will, on the face of it, be a morale-boosting triumph.

It will also almost certainly flatten the few remaining barriers to this bloody conflict turning into an out-and-out sectarian fight between Sunni and Shia that will graft an uncontrollable regional dimension onto what began as an Arab Spring struggle for freedom from tyranny.

Militarily, the narrow corridor between Homs and the Lebanese border is a great prize for both sides. The Homs Gap, as it is sometimes called, has always been the natural gateway from the Syrian coast to the interior; not for nothing did the Crusaders build a line of castles there (including the magnificent Krak des Chevaliers, reportedly already damaged by regime shelling). Read more