The Sasanian World

The empire re-centered: its heart now at Ctesiphon/Madain on the Tigris in the west (not the old Iranian plateau), ringed by four frontiers — Rum across the Euphrates to the west, the Caucasus gate at Darband to the north, the Hephthalites and Turks (“Chin”) beyond the Jihun to the northeast, and the Arab lands to the south — with Hind to the east.