The earliest mentions of Parthia are found in Assyrian texts of the seventh century BC. A civilization developed between the Kopet Dag Mountains and the Dasht-e-Kavir desert in modern-day Iran.
The natives called their land Parthia, from the Persian Parthava. Later records of Herodotus and the Achaemenid’s court records show that Parthia was a governorate of the Achaemenid Empire. Parthia was an Achaemenid province until about 323 BC. It was then a Seleucid governorate, and then home to the rule of the Arsacids.
The Achaemenid Reign
The earliest known rulers of Parthia were the Achaemenid kings. Prior to that, Parthia was under the reign of the Medians, but historical records of the reign are unclear. Cyrus the Great won the allegiance of Parthia with his defeat of the Median ruler, Astyages. The Achaemenid kings administered to Parthia as a satrapy. But when Darius I, the Achaemenid king, ascended the throne, Parthians did not acknowledge him and revolted. This rebellion in 522 BC was further fueled by the support of Median King Phraortes, but was successfully repelled by Hystaspes, the Achaemenid governor of Parthia. The Parthians fought in the Battle of Gaugamela (331 BC) under the command of King Darius III. Alexander the Great of Macedonia defeated Darius III and annexed Parthia in 330 BC.
The Seleucid Reign
With Alexander’s death in 323 BC, his empire was partitioned and Parthia came to be governed by a Seleucid officer, Nicanor. By 320 BC, Philip of Sogdiana took over the administration of the satrapy. Until about 247 BC, a number of Seleucid governors ruled the province. With Ptolemy III’s accession to the throne in 247 BC, Andragoras, the governor of Parthia, declared his independence.
In the following years, Parthia saw a power struggle and much unrest. Arsaces, the Parni leader invaded Parthia in 238 BC. Parthia fell quickly to the invasion and Andragoras died fighting. Seleucid II made an unsuccessful attempt to recapture Parthia from the Parnis but Antiochus III recaptured the region for the Seleucids in 209 BC.
The Arsacid Reign
A descendent of Arsaces, Phraates I ascended the Parthian throne in 176 BC. Phraates I ruled the province independent of Seleucid interference. He is the earliest king of the Arsacid dynasty. His brother, Mithridates I took over in 171 BC, and expanded the Arsacid Empire to include Mesopotamia and Media. Mithridates ruled Parthia until 138 BC, and succeeded in taking the boundaries of the empire as far as the Euphrates River.
By 130 BC, Parthia was attacked repeatedly by various tribes such as the Sakas and the Massagetae. The noble families of Parthia were also dissatisfied with the ruling dynasty, causing much administrative confusion. In 32 BC, Parthia was ravaged by a civil war that caused the downfall of the empire. Repeated wars with Rome and the invading tribes had left Parthia greatly weakened. By 224 AD, Parthia was finally annexed by the Sassanids of Persia.