Seleucids

Originally one of the Companions, Seleucus was one of the more successful of Alexander's generals, securing uncontested control of the eastern portions of the empire by the end of the Successor wars, though not able to hang on to India. His empire was to endure until the first century BC, gradually losing territory to the Parthians and to revolts until finally succumbing to the rising power of Rome.

Although Antiochus III led a partial resurgence in the early second century BC, the loss of Media and the Irania plateau to Parthia in 147 BC cost the Empire its main horse breeding areas and significantly weakened the cavalry arm. After the Maccabean revolt in 145, the last true monarch, Antiochus VII Sidetes, was killed trying to regain the eastern provinces in 129 and the remains were an empire in name only.