The Royal Heartland in 218 B.C.

The Royal Heartland — Seleucid Empire.

The directly-governed centre of the empire: Seleucis — the Syrian tetrapolis of Antioch, Seleucia Pieria, Apamea and Laodicea — together with Mesopotamia, Babylonia and Susiana. Here lay the twin capitals of Antioch on the Orontes and Seleucia on the Tigris, the royal mints, the satrapal administration and the Graeco-Macedonian settlers who were the spine of the army. From Apamea the king drew his phalanx, his cavalry remounts and the Indian elephants that were the signature arm of the dynasty. This was the productive, taxable, defensible core to which every distant satrapy and client king was ultimately bound.