The frontline runs through cotton fields and olive groves: on one side, a powerful Nato member; on the other - a country beset by Islamist militants, the new target of Western military intervention.
Turkey insists its 900km-long (560 mile) border with Syria is a bulwark against Islamic State (IS) and other jihadist groups that have grown during the Syrian war. But its track record tells another story.
Turkey was - for much of the past three-and-a-half-year conflict - the main entry point for weapons, resources and foreign fighters entering Syria.
As a staunch opponent of the Syrian regime, Ankara was seen as adopting a policy of "anyone but [Syrian President Bashar al-] Assad". It was widely criticised for turning a blind eye to the growth of militant groups - or worse, actively encouraging them.
But in the past few months, the situation has changed: 49 Turks - diplomats and their families - were kidnapped by IS in the Iraqi city of Mosul in June and are still being held.