Septimius Severus' Parthian campaigns

Background

The Year of the Five Emperors began with the murder of Commodus on 31 December 192. Pertinax, acclaimed by the Praetorian Guard, was killed after 87 days when the guards mutinied and auctioned the throne to Didius Julianus. Julianus's purchase of power was met with contempt, and within weeks three provincial governors raised their standards: Pescennius Niger in Syria, Clodius Albinus in Britannia, and Septimius Severus in Pannonia Superior. Severus neutralised Albinus by offering him the rank of Caesar, then marched on Italy.

The Senate condemned Julianus to death and acclaimed Severus emperor before the end of May 193. Severus turned on Niger, whose eastern support base was outmanoeuvred. The decisive engagement came at Issus in 194, where Niger's Syrian legions were routed by a cavalry charge under Valerius Valerianus; Niger fled to Antioch, was captured, and executed. In late 195 Albinus was declared a public enemy, and on 19 February 197 the two armies met outside Lugdunum.

Albinus's legions initially drew Severus's forces into prepared fieldworks, but a cavalry charge by Julius Laetus turned the tide. Albinus took his own life. Several eastern rulers had backed Niger: Abgar VIII of Edessa sent troops, the king of Hatra dispatched archers, Narsai of Arbela supported him, and the Parthian king Vologases V ordered his satraps to assemble forces for Niger, though he stopped short of direct intervention.

First Parthian War

In 194, King Abgar VIII of Edessa besieged the Roman fort of Nisibis together with Hatrenene troops to support Pescennius Niger. After Niger was captured and killed, in spring or summer of 195 Severus invaded Mesopotamia to relieve the city. The Roman army crossed the Euphrates near Zeugma and defeated Abgar's forces. The besiegers offered to return prisoners and spoils but asked Severus to evacuate the region; he refused, relieved Nisibis, and marched on Edessa, taking it with little resistance.

Border stones at Kizilburq indicate that the territory surrounding Edessa was incorporated into a new Roman province, while Abgar retained control of the city after promising alliance with Rome, adopting Roman names, giving his sons as hostages, and offering archers. Nisibis was entrusted to the cavalry commander Valerius Valerianus. Severus divided his army into columns under Titus Sextius Lateranus, Tiberius Claudius Candidus, Publius Cornelius Anullinus, Julius Laetus, and a certain Probus.

These columns repelled Arab attacks and conquered an unidentified fortress of importance, possibly by the former governor of Thrace, Titus Statilius Barbarus. The invasion forced the Hatrenenes and Adiabeni of Arbela to seek peace and offer submission.

Second Parthian War

Prompted by the Roman withdrawal from Mesopotamia in 195, Vologases V prepared an invasion. In late summer 197, the Parthians recaptured Armenia, swept through northern Mesopotamia, and besieged Nisibis. The city was saved by the efforts of Julius Laetus, who commanded the garrison. Severus marched through Mesopotamia, reoccupying Armenia after the submission of its ruler Khosrov I, then through Edessa receiving tribute and archers from Abgar VIII, and finally relieved Nisibis.

The Parthians had retreated before Severus arrived, earning him his tenth imperial acclamation. An Iranian revolt inside the Parthian Empire followed. Vologases advanced with 120,000 men to confront the rebels in Khorasan, but after crossing a small river his army was surrounded. During the Parthian retreat, the rebels killed many Parthians, but some Parthian horsemen reorganized and pursued them to the Caspian Sea.

Vologases then met another rebel contingent and defeated it after two days. According to the Chronicle of Arbela, Narsai of Adiabene refused to help Vologases and showed signs of alliance with Rome. Vologases invaded Adiabene, pillaged its capital, and drowned Narsai in the Great Zab. Vologases then led his army into Mesopotamia and won victories against Roman outposts, but because the Parthian army was not a standing force, he left northern Mesopotamia in autumn 196 and returned to Persia.

Aftermath

The permanent extension of Roman rule east of the Euphrates was the most lasting result of Severus’s eastern wars, achieved through the creation of two new provinces. An inscription naming Caius Julius Pacatianus as the first procurator confirms the existence of Osroene, though historians disagree on whether it was founded in 195 or after the second campaign. The full extent of its territory is uncertain because King Abgar VIII kept his own realm in Edessa and continued supplying troops to Severus, indicating that client-royal authority persisted in part of the region.

Mesopotamia was governed by an equestrian prefect who reported directly to the emperor, a system borrowed from Egypt. Nisibis likely served as its capital, receiving colonial status and a new name, Septimia Nisibis, while Singara and Rhesaena were also upgraded to colonies, as were Carrhae and Palmyra. Two legions raised for the eastern wars, Legio I and Legio III Parthica, garrisoned the province. Its borders stretched from the Euphrates in the west to the Tigris in the east, and from the Khabur River in the south to the Djebel Sindjar range; Hatra stayed independent, and Adiabene became a client state across the Tigris.

Syria was split into two provinces, Syria Coele in the north and Syria Phoenice in the south, to reduce its military strength after it had twice supported imperial rivals. Aerial surveys show a sharp rise in small Roman forts throughout the region, and existing garrison towns like Dura-Europos and Anah were reinforced, with fortifications at Palmyra, Apamea, Tayibeh, and Balad Sinjar heavily upgraded.

Did You Know?

• The Historia Augusta reports the wars in a single terse sentence and is almost entirely derivative.
• Cassius Dio relied on Severus' autobiography, as he knew the Emperor personally.
• Aurelius Victor presents a brief description of the campaign with claims conflicting with those of Cassius Dio.