rulers of the empire founded by Seleucus I, governing a vast realm, stretching from Anatolia, via Syria and Babylonia to Iran and thence to central Asia. The Seleucids from the start continued (and adapted) Achaemenid institutions in the army (use of local peoples), in administration (e.g. taxation and satrapal organization; see satrap), colonizing policies, the use of plural ‘royal capitals’ (Seleucia on Tigris, Antioch, Sardis), the use of local languages (and people) in local bureaucracy; also, from the beginning, Babylon, Babylonia, and the Babylonian kingship were central, in Seleucid planning, to an empire, the pivotal point of which, joining east and west, was the Fertile Crescent.
By the peace of Apamea (188), negotiated between Antiochus III and Rome, the Seleucids gave up possessions north of the Taurus mountains in Anatolia, retaining Pamphylia, Cilicia in southern Turkey, plus their large empire in the east. It was the complex interaction of dynastic strife, from the later 2nd cent., the advance of the Parthians, under Mithradates II of Parthia, who had conquered Babylonia by the 120s, and the interference of Rome, that gradually destroyed the Seleucid empire. Pompey annexed Syria in 64 bc, ending just over two and a half centuries of Seleucid rule.