Late Roman Republic, Gaius Octavius (=Octavian), Antony in the East: Parthian Invasion (40-38 BC)

In spring 40 BC, while Antony was in Greece, Pacorus-I of Parthia (r.41-38 BC) and Labienus (2) crossed the Euphrates and invaded Syria with a large force. After defeating Saxa in battle, the two generals separated. Labienus crossed the Taurus, defeated and killed Saxa in battle, and overran southern Asia Minor, while Pacorus advanced into Palestine. In Judea Pacorus defeated the pro-Roman forces of John Hyrcanus II (63-40 BC), Phasael (d.40 BC) and Herod the Great (c.70; r.37-4 BC), and put his Jewish ally Antigonus II (r.40-37 BC) on the throne while Herod fled to his fort in Masada.

In summer 39 BC Antony sent his general Ventidius into Asia Minor to deal with Labienus, while he (Antony) went to Athens with his wife Octavia in order to spend the winter in the city. In late summer Ventidius landed in Asia Minor and catching Labienus by surprise forced him to retreat to Cilicia, where both sides then waited for reinforcements.

When the Parthian heavy knights arrived they, acting independently, charged up the hill where Ventidius had deployed his troops. The slope reduced the knights’ momentum and also therefore their striking power. When they reached the Roman line they had to engage in hand-to-hand combat and were defeated by the legionaries.

Pacorus retreated to northern Syria, leaving a force under Labienus to defend the Cilician Gates (=Gulek Pass), a pass through the Taurus Mountains connecting the Cilician plains to the Anatolian plateau. Ventidius formed his men on a hill and the Parthians, confident of success, surged up the slope to attack them. The Parthian horse-archers unleashed a volley of arrows and the Romans, protecting themselves with their shields, launched their javelins at the Parthians. Eventually Ventidius ordered his infantry into close order and charged down the hill. The lightly-armoured horse-archers could not hold their own against the heavily armoured legionaries and Parthian forces broke and fled. After the battle Labienus was captured and executed.

After this defeat the general Pharnapates, in charge of the Parthian forces in northern Syria, sent a strong detachment to defend the Syrian Gates (=Belen Pass), a narrow pass through the Amanus (=Nur) Mountains connecting coastal Cilicia to inland Syria. Ventidius sent an officer Pompaedius Silo with some cavalry to capture this position. He was drawn into an engagement with the enemy and was losing the fight until Ventidius arrived with the rest of his forces. The Parthians were overpowered and defeated; Pharnapates himself was among those slain.

Pacorus temporarily withdrew from Syria and then returned in the spring of the following year. He crossed the Euphrates unopposed and proceeded to the town of Gindarus in the northwest corner of Syria, where he found the Romans formed up on the slopes of a hill. The Parthians, apparently not having learned from their earlier defeats, rushed up the slope. Ventidius ordered his troops to attack the horse-archers, which broke and once more panic spread among the ranks. Pacorus and the Parthian heavy cavalry at the bottom of a hill were attacked first by slingers throwing projectiles and when the barrage ended the legionaries moved in. Pacorus was identified and killed along with his bodyguards, and the survivors of his force retreated across the Euphrates.

After Gindarus the final pocket of resistance was in the city of Samosata (Samsat), on the west bank of the upper Euphrates in southeast Asia Minor, which was defended by the vassal king Antiochus-I (c.48; r.70-38 BC). Ventidius put the city under siege and a few months later (midsummer) Antony arrived and took command. Ventidius returned to Rome and was allowed to celebrate his victories with a triumph.

As the siege of Samosata was nearing its end Herod arrived seeking Roman aid to defeat Antigonus II, who was in possession of Jerusalem, and become king himself. He was well received by Antony, who ordered Sosius (cos.32 BC), who had succeeded Ventidius in the Roman command, to give Herod all assistance possible. In spring 37 BC all Judaea, except for the capital, fell to Herod and he resumed a siege of Jerusalem. Sosius’ new force then arrived, and in July the city fell. After the surrender of Samosata, Antony put Sosius in charge of Syria and he himself left the province.