Parthia

Satrapy of the Achemenid empire, southeast of the Caspian Sea. After the fall of the Achemenids, Parthia was settled by the nomadic Parni from the east Caspian steppe region. Their ruling Arsacid dynasty became vassals of the Seleucid kingdom until Arsaces I established Parthian independence in 238 BC. Mithradates I (r.170-138 BC) turned Parthia into a major power by conquering Persia and Mesopotamia. In the 1st century BC, Parthia came under attack by the Roman empire. Despite a crushing victory over the Romans at Carrhae (53 BC), a long series of debilitating wars followed. The Arsacid dynasty fell and and the Parthian empire was taken over by the Persian Sasanian dynasty in AD 224-26. Under the Arsacids Parthia developed as a decentralized feudalistic state.