Parthian invasion of 40 BC

Pompeian–Parthian invasion of 40 BC
Part of the Roman–Parthian Wars
Date40–38 BC
Location
Result Roman Republic victory
Territorial
changes
Status quo ante bellum
Belligerents
Parthian Empire
Roman Pompeians
Pro-Parthian Judeans
Commagene
Roman Republic
Pro-Roman Judeans
Commanders and leaders
Orodes II
Pacorus I of Parthia 
Quintus Labienus 
Pharnapates 
Antigonus II Mattathias 
Antiochus I of Commagene
Mark Antony
Lucius Decidius Saxa 
Lucius Munatius Plancus (withdrawn)
Publius Ventidius
Pompaedius Silo
Hyrcanus II 
Phasael 
Herod
Strength
Estimated ~14,000 Parthian cavalry
Unknown number of Republican Roman soldiers
Estimated ~54,000 men (in total) (~11 legions, cavalry, slingers)

The Parthian invasion of 40 BC was an attempt by the Parthian Empire to take control of the Eastern Mediterranean area from the Roman Republic, while its leaders were struggling for power in Italy. Initially successful, the invasion was defeated by the Roman general Publius Ventidius.

The Roman Republic had been at war with the Parthian Empire since the disastrous invasion of Crassus in 53 BC. Nevertheless, during the Liberator's civil war (43–42 BC), Brutus and Cassius dispatched Quintus Labienus to the court of king Orodes II to request his help against the Second Triumvirate, but they had already been defeated before he could join. Labienus therefore stayed at the Parthian court.

In 41 BC, the alliance between the triumvirs Octavian and Mark Antony faltered with the Perusine War in Italy, which prompted the Parthians to attack the following year. The Parthian heir Pacorus conquered Palestine, while Labienus campaigned in Syria, recruiting the former soldiers of Brutus and Cassius. Without much opposition, he conquered almost all of Anatolia.

In 39 BC, Antony sent his most able general, Publius Ventidius, to repel the invasion. Ventidius' counterattack was swift and he managed to reconquer all the lost territories in one year, killing Labienus and Pacorus in the process. Antony may have ordered Ventidius to stop advancing at this point, as his successes could overshadow Antony's own invasion of the Parthian Empire that he was planning.