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. The fight for al-Safira is no ordinary turf war, however, and the prize can be found behind the perimeter walls of the heavily-guarded military base on the edge of town. Inside what looks like a drab industrial estate is one of Syria's main facilities for producing chemical weapons - and among its...