After the defeat of the Parthian-backed Pompeians in the Liberators' civil war by Mark Antony and Octavian, Orodes II sent a Parthian force under Prince Pacorus I and the Pompeian general Quintus Labienus in 40 BC to invade the eastern Roman territories while Antony was in Egypt. Roman soldiers in Syria, many of whom were former Republicans fighting in the last civil war, joined the force, and the Levant and much of Asia Minor were swiftly overrun by Pacorus I and Labienus, respectively. In 39 BC, Antony sent Ventidius, who defeated and executed Labienus in a counter-attack, and then drove Pacorus I out of the Levant.