Julius Caesar had planned an invasion of Parthia, but he was assassinated before implementing it. In 40 BC, the Parthians were joined by Pompeian forces and briefly captured much of the Roman East, but a force sent by Antony defeated them and reversed their gains.
Allying with several kingdoms, including Armenia, Antony began a campaign against Parthia with a massive force in 36 BC. The Euphrates front was found to be strong, so Antony chose the route via Armenia. Upon entering Atropatene, the Roman baggage train and siege engines, which had taken a different route, were destroyed by a Parthian cavalry force. Antony nevertheless besieged the Atropatenene capital, but failed. The arduous journey of retreat to Armenia and then Syria further inflicted heavy losses on his force. Roman sources blame the Armenian king for this heavy defeat, but modern sources note Antony's poor management and planning. Antony later invaded and pillaged Armenia and executed its king.
The war became a strategic draw when peace was later negotiated by Augustus.
Julius Caesar, after ensuring victory in his civil war, planned a campaign into the Parthian Empire in 44 BC. to avenge the earlier defeat of a Roman army led by Marcus Licinius Crassus at the Battle of Carrhae. Caesar's plan was, after a brief pacification of Dacia, to continue east into the Parthian territory. After his assassination, the Second Triumvirate, composed of Marcus Antonius (Antony), Marcus Lepidus and Gaius Octavianus (later known as Augustus), was formed. After the defeat of Caesar's assassins at the Battle of Philippi, Caesarian rule over the Republic was effectively ensured. Shortly after, however, with the triumvirs preoccupied with the revolt of Sextus Pompey in Sicily, Parthia attacked Roman-controlled Syria and the client kingdom of Judea. The Judean high priest and puppet Roman ruler, Hyrcanus II, was overthrown and sent as prisoner to Seleucia, and the pro-Parthian Hasmonean Antigonus was installed in his place. Antigonus was the only remaining son of the former king Aristobulus II who the Romans deposed when they installed the weaker Hyrcanus II as high priest (but not king) in 63 BC. Upon capturing Hyrcanus II, Antigonus bit off his uncle's ears to disqualify him from ever again serving as high priest.
In Anatolia, the Parthians allied with Quintus Labienus, son of Caesar's former general and later antagonist Titus Labienus, penetrating deep into the west and defeating a Roman army under Decidius Saxa. They were however defeated in turn by a veteran army led by Publius Ventidius Bassus, who drove the invaders from Roman territory.
In 36 BC, Antony went on to attack the Parthian Empire. Having 16 legions (~60,000 legionaries), he joined with forces from the client kingdoms of Galatia, Cappadocia, Pontus, and Armenia. The invasion force reached a total of 100,000 men. As the Parthians were concentrated on the Euphrates, Antony chose the route via Armenia towards Atropatene. From there, Antony and the bulk of the force took the convenient caravan route. The baggage train, which was under legatus Oppius Statianus and accompanied by King Artavasdes II of Armenia, took a different, longer route. After entering Atropatene, the latter convoy was attacked by a Parthian cavalry force under Monaeses. Statianus and 10,000 legionaries were killed and the Antony's supplies and siege engines were destroyed. King Polemon I of Pontus was captured, but King Artavasdes II and his cavalry had hastily retreated and thus did not engage. The retreat of the Armenian king was later interpreted as treason in Antony's camp. However, a pro-Antony bias is present in the narrations of the campaign by Strabo and Plutarch, whose primary source was a written report by Antony's friend, Quintus Dellius, who had masked Antony's poor management and put the blames on the Armenian king.
Antony nevertheless proceeded to besiege the fortified Atropatenian capital Phraata/Praaspa (identified as either Maragheh or less probably Ganzak/Takht-e Soleyman). Ceaselessly harassed by the Parthian and Atropatenian cavalry, Antony finally abandoned the siege and realized the defeat.
Antony then began an exhausting retreat along a mountainous road, while ceaselessly harassed by the Parthian cavalry, until they reached the border of Armenia Major after twenty-seven days. A survey of the troops suggested 24,000 men were lost. In Armenia, Antony hid his resentment of the Armenian king and his intentions to punish the king in the future, as he needed his support to continue his journey through Armenia back to the Roman soil in Syria. The arduous journey through the mountains of Armenia in winter greatly reduced the strength of Antony's army. Around 32,000 men of his army were lost in total.
Again with Egyptian money, Antony invaded Armenia, this time successfully. On his return to Egypt, the equivalent of a Roman Triumph was celebrated in the streets of Alexandria. At the end of the celebration, the whole city was summoned to hear a very important political statement to be known as the Donations of Alexandria. This political statement effectively ended Antony's alliance with Octavian.
The Parthian king Phraates IV was unable to follow up the victory due to a civil war lasting from 32/1 BC to 25 BC began by the rebellion of Tiridates, which was probably supported by aristocratic circles and the Romans.
- Bivar, H.D.H (1968). William Bayne Fisher; Ilya Gershevitch; Ehsan Yarshater; R. N. Frye; J. A. Boyle; Peter Jackson; Laurence Lockhart; Peter Avery; Gavin Hambly; Charles Melville (eds.). The Cambridge History of Iran. Cambridge University Press. p. 59. ISBN 0-521-20092-X.
- Chaumont, M. L. (5 August 2011). "ANTONY, MARK". Encyclopaedia Iranica.
- Freeman, Philip. Julius Caesar. Simon and Schuster (2008) ISBN 978-0743289542, p.347-349
- Jewish Wars I 13:9
- Schottky, Martin (Pretzfeld) (1 October 2006). "Monaeses". In Salazar, Christine F. (ed.). Brill's New Pauly. doi:10.1163/1574-9347_bnp_e808670. ISBN 9789004122598.
- Smith, Sir William (1849). Dictionary of Greek and Roman Biography and Mythology. C.C. Little and J. Brown. p. 39a.
- Ussher, James; Pierce, Larry; Pierce, Marion (2003). The Annals of the World. New Leaf Publishing Group. p. 717b. ISBN 978-0-89051-360-6.
- K. Schippmann, “ARSACIDS ii. The Arsacid dynasty,” Encyclopaedia Iranica, II/5, pp. 525-536, available online at http://www.iranicaonline.org/articles/arsacids-ii (accessed on 30 December 2012).