Parthian invasion of 40 BC

The Parthians had defeated and killed Marcus Licinius Crassus, a member of the First Triumvirate along with Julius Caesar and Pompey, at the Battle of Carrhae. They had also maintained relations with Pompey but never supported him militarily during Caesar's civil war. After Pompey's death, Caesar planned an invasion of Parthia but was assassinated before he could implement it. In 42 BC, Parthian forces fought against the Caesarians under Mark Antony and Octavian in the Battle of Philippi during the Liberators' civil war. After the defeat of the Liberators, who had assassinated Caesar, Quintus Labienus, a general who attempted to resurrect the Pompeian cause and had been sent to Parthia to ask for assistance in the last civil war, joined the Parthians. King Orodes II sent him and his son Pacorus I to invade eastern Roman territories while Antony was in Egypt with Cleopatra. ==Invasion==

Orodes II sent his son Pacorus I as well as Labienus as the commanders of a large Parthian army to invade Roman territory in early 40 BC (or late 41 BC, according to some scholars). According to Vagi, the invasion comprised some 20,000 horsemen. Many Roman forces in Syria defected to Labienus. Antony's commander in Syria, Lucius Decidius Saxa, fled to Antioch and then to Cilicia, where he was captured by Labienus and executed. Several Roman aquilae were then captured by the Parthians. (The aquilae, together with ones captured after the Battle of Carrhae, were later returned after Augustus's negotiations with the Parthians.) Apamea and Antioch surrendered. The two commanders split. Pacorus invaded Palestine and Phoenicia that captured much of the region. He was hailed as imperator. Antony left Egypt for Greece and sent Publius Ventidius to Asia Minor. He scored two victories with minimal forces north of the Taurus Mountains in 39 BC (Battle of the Cilician Gates, Battle of Amanus Pass) and captured and executed Labienus. He then drove the Parthians out of Syria. Another Parthian invasion of Syria in 38 BC under Pacorus I resulted in a decisive defeat at the Battle of Mount Gindarus in Cyrrhestica, with Pacorus I being killed and the Parthian presence in Syria being brought to an end. ==Aftermath==

In 38 BC, Mark Antony finally began his campaign against Parthia with a large force, but it resulted in a defeat with heavy Roman losses. ==References==