Turkey's Prime Minister Ahmet Davutoglu was in London last week, telling the Western media how helpful Ankara was being in the struggle against the terrorist "Islamic State" that has emerged in northern Syria and Iraq. Turkey is doing everything it can, he said — although, of course, "We cannot put troops everywhere on the border."

Turkey's open border has become a sore point with its Western allies, who suspect that President Recep Tayyip Erdogan is deliberately allowing a steady flow of recruits and supplies to "Islamic State" because he still wants the Sunni rebels, most of whom are jihadi extremists, to overthrow Bashar Assad, Syria's Shiite ruler. (Erdogan is no jihadi, but he is a devout and militant Sunni Islamist.)

But Erdogan's motives are irrelevant, because Turkey simply cannot put troops everywhere on its 820 km border with Syria. Or so says Ahmet Davutoglu, and only an enemy of Turkey (or somebody with a grasp of basic mathematics) would say otherwise.