mi) back to Seleucia where his victory was celebrated. However, fearing his ambitions even for the Arsacid throne, Orodes had Surena executed shortly thereafter. Emboldened by the victory over Crassus, the Parthians attempted to capture Roman-held territories in Western Asia. Crown prince Pacorus I and his commander Osaces raided Syria as far as Antioch in 51 BC, but were repulsed by Gaius Cassius Longinus, who ambushed and killed Osaces. The Arsacids sided with Pompey in the civil war against Julius Caesar and even sent troops to support the anti-Caesarian forces at the Battle of Philippi in 42 BC. Quintus Labienus, a general loyal to Cassius and Brutus, sided with Parthia against the Second Triumvirate in 40 BC; the following year he invaded Syria alongside Pacorus I. The triumvir Mark Antony was unable to lead the Roman defense against Parthia due to his departure to Italy, where he amassed his forces to confront his rival Octavian and eventually conducted negotiations with him at Brundisium. After Syria was occupied by Pacorus' army, Labienus split from the main Parthian force to invade Anatolia while Pacorus and his commander Barzapharnes invaded the Roman Levant. They subdued all settlements along the Mediterranean coast as far south as Ptolemais (modern Acre, Israel), with the lone exception of Tyre. In Judea, the pro-Roman Jewish forces of high priest Hyrcanus II, Phasael, and Herod were defeated by the Parthians and their Jewish ally Antigonus II Mattathias (r. 40–37 BC); the latter was made king of Judea while Herod fled to his fort at Masada. Despite these successes, the Parthians were soon driven out of the Levant by a Roman counteroffensive. Publius Ventidius Bassus, an officer under Mark Antony, defeated and then executed Labienus at the Battle of the Cilician Gates (in modern Mersin Province, Turkey) in 39 BC. Shortly afterward, a Parthian force in Syria led by general Pharnapates was defeated by Ventidius at the Battle of Amanus Pass. As a result, Pacorus I temporarily withdrew from Syria. When he returned in the spring of 38 BC, he faced Ventidius at the Battle of Mount Gindarus, northeast of Antioch. Pacorus was killed during the battle, and his forces retreated across the Euphrates. His death spurred a succession crisis in which Orodes II chose Phraates IV (r. c. 38–2 BC) as his new heir. Upon assuming the throne, Phraates IV eliminated rival claimants by killing and exiling his own