250 Foundation of an independent monarchy by Arsaces I. Antiochus, on account of civil and foreign wars, is unable to proceed against Arsaces.
248 Death of Arsaces. His brother, Tiridates, succeeds, taking the name of Arsaces, which is also borne by all his successors as a throne name. They take the title of “king of kings.”
242 After defeat of Seleucus Callinicus at Ancyra, Tiridates invades Parthia, slays the eparch Andragores, and takes possession of the province. He next seizes Hyrcania, and causes a large army to oppose Seleucus.
238 Decisive victory of Tiridates over Seleucus. The latter is obliged to return to Antioch on account of civil war, and Tiridates is enabled to consolidate his kingdom.
211 Death of Tiridates. His son, Arsaces II, sometimes, but incorrectly, called Artabanus, succeeds.
209 Antiochus the Great wins a victory over Arsaces on the summit of Mount Labus. The Parthians retire to Sirynca and are besieged by Antiochus. Surrender of Sirynca, and treaty of peace. Arsaces retains Parthia, but is reduced to a vassal of Antiochus. Parthia remains undisturbed for some years.
191 Phriapatius or Arsaces (III) Philadelphus succeeds his father. Owing to the decay of Seleucid power, he acts as protector of the Greeks in his kingdom.
176 Phraates I or Arsaces (IV) Theopator succeeds his father. He conquers the Mardians.
171 Phraates dies, leaving the throne to his brother, Mithridates I or Arsaces (V) Epiphanes, who at once annexes several satrapies of Bactria to his kingdom. He holds court in Hyrcania.
155 At death of King Eucratides of Bactria, Mithridates continues the conquest of that country. The Hindu Kush becomes the eastern boundary of Parthia. Mithridates turns to the west.