In the long history of the Roman Republic, many generals were hailed as Imperator, but only one bore the bizarre and paradoxical title of Imperator Parthicus: Quintus Labienus. A man without a country, Labienus led a foreign superpower against his own people, becoming one of the most dangerous renegades Rome ever produced.
The Son of a Legend
Quintus was the son of Titus Labienus, Julius Caesar‘s most brilliant lieutenant in Gaul who later became Caesar’s most bitter enemy during the Civil War. Inheriting his father’s tactical mind and deep-seated hatred for the Caesarean faction, Quintus aligned himself with the “Liberators,” Brutus and Cassius, after the Ides of March.
In 42 BC, just before the Battle of Philippi, Cassius sent Labienus on a desperate diplomatic mission: to seek military aid from Rome’s greatest rival, the Parthian Empire.
The Great Invasion of 40 BC
While Labienus was at the Parthian court of King Orodes II, news arrived of the defeat and suicides of Brutus and Cassius. Trapped in exile and marked for death by the Second Triumvirate, Labienus convinced the Parthians that the Roman East was ripe for the taking.
In 40 BC, Labienus and the Parthian prince Pacorus I crossed the Euphrates at the head of a massive army. The invasion was devastatingly successful:
• The Defection: Many Roman garrisons in Syria, formerly under the command of Brutus and Cassius, recognized Labienus and defected to him rather than fighting for Mark Antony.
• The Conquest: Pacorus moved south toward Judea and Jerusalem, while Labienus swept through Asia Minor (modern-day Turkey), conquering cities and driving out Antony’s governors.
The Title: Imperator Parthicus
It was during this campaign that Labienus took the unprecedented step of minting his own coinage. These coins are among the most striking artifacts of the era. They feature his portrait on the obverse and, most shockingly, a Parthian horse—the symbol of Rome’s greatest enemy—on the reverse.
The coins bear the legend Q. LABIENVS PARTHICVS IMP. While the title “Parthicus” was usually granted to Romans who conquered Parthia, Labienus used it to signify his command over Parthian troops. He was, quite literally, the “Parthian General” leading a foreign invasion of his own homeland.
The Fall at Mount Taurus
The success of Labienus was short-lived. In 39 BC, Mark Antony’s talented lieutenant, Publius Ventidius Bassus, arrived with a veteran relief force.
Ventidius was a master of terrain. He cornered Labienus’s forces near the Taurus Mountains in Cilicia. Labienus, relying on Parthian heavy cavalry, was unable to break the Roman heavy infantry positioned on the heights. When the Parthian reinforcements were routed, Labienus’s Roman defectors abandoned him.
Labienus fled in disguise but was eventually captured and executed.
Legacy of the Renegade
Quintus Labienus remains a unique and controversial figure. To the Romans, he was the ultimate traitor—a man who showed the “barbarians” the way into the heart of the Republic. Yet, his ability to command both Roman legions and Parthian cataphracts showed a tactical flexibility that nearly toppled Roman rule in the East.
His death marked the end of the last organized resistance from the faction of Brutus and Cassius, leaving the world to be fought over by Antony and Octavian.