Mithridates I (also spelled Mithradates I or Mihrdad I; Mihrdāt), also known as Mithridates I the Great, was king of the Parthian Empire from 165 BC to 132 BC. During his reign, Parthia was transformed from a small kingdom into a major political power in the Ancient East as a result of his conquests. He first conquered Aria, Margiana and western Bactria from the Greco-Bactrians sometime in 163–155 BC, and then waged war with the Seleucid Empire, conquering Media and Atropatene in 148/7 BC. In 141 BC, he conquered Babylonia and held an official investiture ceremony in Seleucia. The kingdoms of Elymais and Characene shortly afterwards became Parthian vassals. In BC, while Mithridates was fighting the nomadic Saka in the east, the Seleucid king Demetrius II Nicator attempted to regain the lost territories; initially successful, he was defeated and captured in 138 BC, and shortly afterwards sent to one of Mithridates I's palaces in Hyrcania. Mithridates I then punished Elymais for aiding Demetrius, and made Persis a Parthian vassal.
Mithridates I was the first Parthian king to assume the ancient Achaemenid title of King of Kings. Due to his accomplishments, he has been compared to Cyrus the Great (), the founder of the Achaemenid Empire. Mithridates I died in 132 BC, and was succeeded by his son Phraates II.
Name
"Mithridates" is the Greek attestation of the Iranian name Mihrdāt, meaning "given by Mithra", the name of the ancient Iranian sun god. The name itself is derived from Old Iranian Miθra-dāta-. Mithra is a prominent figure in Zoroastrian sources, where he plays the role of the patron of khvarenah, i.e. kingly glory. Mithra played an important role under the late Iranian Achaemenid Empire, and continued to grow throughout the Greek Seleucid period, where he was associated with the Greek gods Apollo or Helios, or the Babylonian god Nabu. The role of Mithra peaked under the Parthians, which according to the modern historian Marek Jan Olbrycht, "seems to have been due to Zoroastrian struggles against the spread of foreign faiths in the Hellenistic period."
Background
Mithridates was the son of Priapatius, the great-nephew of the first Arsacid king, Arsaces I (). Mithridates had several brothers, including Artabanus and his older brother Phraates I, the latter succeeding their father in 176 BC as the Parthian king. According to Parthian custom, the reigning ruler had to be succeeded by his own son. However, Phraates I broke tradition and appointed his own brother Mithridates as his successor. According to the 2nd-century Roman historian Justin, Phraates I had made his decision after noticing Mithridates' remarkable competence.
Reign
The kingdom that Mithridates inherited in 165 BC was one of the many medium-sized powers that had risen with the decline of Seleucid Empire or had appeared on its borders. Other kingdoms were Greco-Bactria, Cappadocia, Media Atropatene, and Armenia. Mithridates I's domains encompassed present-day Khorasan Province, Hyrcania, northern Iran, and the southern part of present-day Turkmenistan.
Wars in the east
He first turned his sights on the Greco-Bactrian Kingdom which had been considerably weakened as a result of its wars against the neighbouring Sogdians, Drangianans and Indians. The new Greco-Bactrian king Eucratides I () had usurped the throne and was as a result met with opposition, such as the rebellion by the Arians, which was possibly supported by Mithridates I, as it would serve to his advantage. Sometime between 163–155 BC, Mithridates I invaded the domains of Eucratides, whom he defeated and seized Aria, Margiana and western Bactria from. Eucratides was supposedly made a Parthian vassal, as is indicated by the classical historians Justin and Strabo. Merv became a stronghold of Parthian dominance in the northeast. Some of Mithridates I's bronze coins portray an elephant on the reverse with the legend "of the Great King, Arsaces." The Greco-Bactrians minted coins with images of elephants, which suggests that Mithridates I's coin mints of the very animal was possibly to celebrate his conquest of Bactria.