Phraates I ( Frahāt) was king of the Arsacid dynasty from 170/168 BC to 165/64 BC. He subdued the Mardians, conquered their territory in the Alborz mountains, and reclaimed Hyrcania from the Seleucid Empire. He died in 165/64 BC, and was succeeded by his brother Mithridates I (), whom he had appointed his heir. Name Phraátēs () is the Greek transliteration of the Parthian name Frahāt (𐭐𐭓𐭇𐭕), itself from Old Iranian *Frahāta- ("gained, earned"). The Modern Persian version is Farhād (). Background Phraates was the eldest son of the Parthian monarch Priapatius (), who was the nephew of Arsaces II. Phraates had three other brothers, Mithridates, Bagasis and Artabanus. New epigraphic evidence from Nisa suggests that Priapatius following his death in 170 BC may have been succeeded by an obscure figure named Arsaces IV, who briefly ruled for two years. However, this is rejected by the historian Marek Jan Olbrycht, who calls it "sheer speculation". Since the defeat of Arsaces II against the Greek Seleucid Empire in 208, the Parthians had been their subordinate ally. However, with the decline of the Seleucids in the 180s BC, the Parthians were able to reassert much of their former autonomy. Reign At the start of 165 BC, Phraates attacked the powerful Mardians (also known as Amardians), a people who lived in Alborz mountains, which bordered Hyrcania in the east and Media in the southwest. Owing to their geographical position, the Mardians were able to pose a threat to the trade routes stretching from Hyrcania and western Parthia to western Iran. The attack was probably part of the Parthian efforts to expand their domain in Iran proper and secure control over Hyrcania. The main aspiration of the Parthians was to conquer Media, starting with Media Rhagiane. Phraates' attack on the Mardians was successful, conquering the Caspian Gates, as well as the city of Charax, which was close to the Median metropolis of Rhaga. Furthermore, he also reclaimed Hyrcania from the Seleucids. He had a group of Mardians deported to Charax to protect the Caspian Gates, and the Tapurians in Parthia deported to the Caspian coast, which gave rise to the name of the historical region Tabaristan. Phraates' conquests paved the way for his successors to further expand the Parthian realm. Phraates' western expansion was a transgression of the traditional status quo between the Parthians and Seleucids. During this period, the Seleucids were occupied in