Set amid the rolling plains outside Aleppo, the town of al-Safira looks just like another vicious battleground in Syria's civil war. On one side are lightly-armed rebels, on the other are government troops, and in between is a hotly-contested no-man's land of bombed-out homes and burned-out military vehicles.
Last week, Washington said for the first time that it had evidence of Sarin being used in "small" amounts during combat operations in Syria, a move that President Barack Obama has long warned is a "red line" that President Bashar al-Assad must not cross.
But as the West now ponders its response, the fear is not just that President Assad might start using his chemical arsenal in much greater quantities. Of equal concern is the prospect of it falling into even less benign hands - a risk that the stand-off at al Safira illustrates clearly.