During the reign of Mithridates I of Parthia, Arsacid control expanded to include Herat (in 167 BC), Babylonia (in 144 BC), Media (in 141 BC), Persia (in 139 BC), and large parts of Syria (in the 110s BC). The Seleucid–Parthian wars continued as the Seleucids invaded Mesopotamia under Antiochus VII Sidetes (r. 138–129 BC), but he was eventually killed by a Parthian counterattack. After the fall of the Seleucid dynasty, the Parthians fought frequently against neighbouring Rome in the Roman–Parthian Wars (66 BC – 217 AD). Abundant traces of Hellenism continued under the Parthian empire. The Parthians used Greek as well as their own Parthian language (though lesser than Greek) as languages of administration and also used Greek drachmas as coinage. They enjoyed Greek theater and Greek art influenced Parthian art. The Parthians continued worhipping Greek gods syncretized together with Iranian deities. Their rulers established ruler cults in the manner of Hellenistic kings and often used Hellenistic royal epithets.

The Seleucids invaded Mesopotamia under whose guidance?