Interconnected Frontiers: Trans-Caspian Defensive Networks of the Sasanian Empire

Fieldwork, under the auspices of the ERC-funded ‘Persia and its Neighbours’ project (2012–2018), has shed fascinating new light on defensive strategies of the Sasanian Empire. Between the fourth and the sixth century AD, Persia built up the most massive military infrastructure of any Near Eastern empire–rivalling if not dwarfing that in the late Roman world. The largest Sasanian fortresses exceed the average late Roman legionary fortress by a factor of 30, the longest fort-lined Sasanian frontier wall is more than three times the length of its longest late Roman counterpart. Yet these monuments are remarkable not only for their sheer scale, but form part of a sophisticated system. Architecturally similar megafortresses are found to the west, east and south of the Caspian Sea, from northern Iran to modern Dagestan. The largest, near Tehran, may have played a central role, and there is archaeological and written evidence to suggest that these fortifications served as temporary bases for large mobile armies. Our project has succeeded in precisely dating three more of these vast purpose-built military compounds. At least two of them are earlier than the fifthcentury Great Wall of Gorgan, and they are contemporary to the pass defences of Dariali Gorge in modern Georgia (or up to a few decades younger or older). The skilful use of its natural mountain barriers, notably the Caucasus, Alborz and Hindu Kush, and a sophisticated network of artificial fortifications enabled the Sasanian empire, by and large, to hold its enemies at bay and create the right conditions for inner prosperity and urban growth.