The strategic significance of the Dariali Gorge, the main pass across the central Caucasus, has long been recognised. It forms a border today as it has done for much of the past 2000 years. But how was an effective military force sustained in an isolated Alpine environment? Excavations, osteoarchaeology and landscape survey have revealed that the Early Middle Ages saw as much investment in controlling this key route as there was in Antiquity. Guarded by the same Muslim-led garrison for at least a quarter of a millennium, its survival in a harsh environment was made possible through military effort and long-distance food supplies.