Trajan's Parthian War
Background to the Invasion
In 114 AD the Roman Emperor Trajan embarked on a campaign of conquest aimed at the Parthian Empire, Rome's eastern nemesis. In this campaign the emperor marched further than any of his predecessors against the Parthians, but his success was short-lived.
Rumblings of war began to be heard from early in Trajan's reign. Previously the peace was kept by the so-called “Neronian Settlement” of 63 where the Parthian Great King Valaksh (Vologases) I and Emperor Nero struck a compromise over control of the strategically important Kingdom of Armenia and the Caucasus region. By the terms of the compromise, Parthia could name a candidate for the Armenian throne, but Rome had to approve and formally crown him. By the early 100s the agreement was breaking down as relations between Rome and Parthia cooled. It is unclear but between 100 and 109 the Parthians invaded Armenia and placed a Prince Axidares (alternatively Exedares) on the throne. The Romans chose to accept Axidares, but still considered the invasion an insult. Trajan was seemingly planning to invade as early as 111-12. He began minting military-themed coins, deified his father, one of the few Roman generals to be honored for an eastern campaign, and appointed Hadrian (Trajan's cousin and future emperor) to Syria. Coinciding with Hadrian’s journey was the restoriation of the Via Egnatia, a 250 mile road from Dyrrachium to Acontismaa and the primary land route from Italy to the Roman east over the course of 112.
In 113 the new great king, Osrow (Osroes) I, tried to depose Axidares in favor of the latter's older brother, Parthamasiris. The official reason, as told to Trajan by an embassy later, was that Axidares had failed to keep the peace in Armenia. Unofficially it seems likely that Osrow was trying peacefully to displace a rival to the throne. Parthia now was gripped by dynastic civil wars, and Parthamasiris had a good claim as the oldest son of Osrow's predecessor (and older brother). By autumn 113 the Roman emperor had already left Rome and was headed for Antioch. The Parthians met him at Athens with an embassy and suggested Parthamasiris be officially recognized as king of Armenia. To appease Roman dignity Osrow offered to have Parthamasiris return the crown and have the emperor formally confirm him, according to the terms of the Neronian Settlement. Trajan refused to listen, returned the Great King's gifts, and remarked that friendship and diplomacy were determined by deeds, not words. He continued east and arrived at Seleucia-in-Pieria in late December where he met Hadrian and entered Antioch in the first days of January, 114.
The Question of Armenia
Trajan's reasons for deciding on war are unknown but are likely a combination of the following three factors: First, to solve the “Armenian question” decisively. Second, to follow up on the success of his policy of annexation as pursued in Dacia and Nabatea. Last, it could have been simply to win renown in war and surpass his previous military achievements. All are all valid guesses about Trajan’s reasons for pursuing war against Parthia.
Anyway the emperor was greeted in Antioch by a large army already prepared by Hadrian. He would pass the time until the beginning of the campaign season in spring by conducting the business of empire and diplomacy with the border kingdoms caught between the superpowers. These were Osrhoene (which tried to remain neutral), the Scenite Arabs, and Anthemusia. In early April a second embassy arrived from Osrow asking for Trajan's decision on his offer at Athens. The emperor responded he had no wish for war, but the terms were unacceptable and therefore rejected. He then set off for Satala, the chosen headquarters for the year.
From Antioch Trajan traveled to Beroea and from there to the fortress of Zeugma, picking up Legion IV Scythia there. From Zeugma the Romans crossed Euphrates to march over the modern Kanliavsar watershed to Samosata and picked up Legion VI Ferrata. They then crossed back over the left bank of the Euphrates, over the modern Malatya Daglari to Melitene to be joined by Legion XII Fulminata. While at Melitene the emperor received a letter from Parthamasiris asking him for recognition as king and formal investiture. The tone of the letter, combined with Parthamasiris signing it “King of Armenia” rankled Roman sensibilities and Trajan refused to reply until the arrival of a second, much more humble, letter. This time the Parthian prince simply asked for the opening of negotiations through the governor of Cappadocia. The emperor refused but sent the governor's son to verify the terms under offer. From Melitene they crossed the Euphrates a third time, marching through the Elazig Pass to the hostile city of Arsamosata, which was invested without difficulty. From Arsamosata the army marched through the Pulumur Pass, crossed the Euphrates for the final time, and arrived at Eriza, one day from Satala and picked up Legion XVI Flavia Firma.
The imperial army arrived in Satala in late May. Here Trajan had assembled seven Legions at full or slightly below full strength. Supplies had been flowing into Satala from Tomis in modern Romania along the Black Sea route to Trapezus and then over the Zigana Pass to headquarters. The Danubian Legions had been sending contingents over the winter by way of Ancyra to reinforce the army. In all Trajan had some 80,000 men, the equivalent of eight full Legions, to command as he left Satala for Elegeia to meet Parthamasiris in early June. But the prince was late to the meeting, naming partisans of his brother Axidares (still holding out in the northwest) as being responsible. In any case Parthamasiris appeared before the emperor to lay down his crown, believing he would now be named the legitimate King of Armenia. But Trajan left the crown where it lay. Instead his soldiers began to hail him as imperator, just like after a military victory. The emperor proclaimed Armenia was now a Roman province. Also, he had no intention of surrendering the territory or Rome’s sovereignty over it. A governor was appointed and the Armenian nobility accompanying Parthamasiris informed that as Roman subjects they would remain with the camp. The deposed prince was then given an escort and sent on his way. His death shortly after that under mysterious circumstances is typically attributed to Trajan's doing.
The First Strokes
The emperor's generals now set about bringing Armenia into line. Four divisions marched out from headquarters under Lusius Quietus, C. Bruttius Praesens, and two unknown commanders. Quietus' division advanced down the Araxes River valley and subdued the Mardi before pushing onwards to take control of the vital Bitlis Pass south of Lake Van. Praesens had gone into the highlands and was still fighting late into the winter. The third division advanced as far east as the Caspian Gates and seemingly remained in Armenia for several years. The fourth marched beyond Armenia proper and occupied the Caucasian Gates and Dariel Pass. By year's end Trajan's first stroke had succeeded brilliantly. The Romans had occupied all key points and isolated the resistance by a network of forts while consolidating their new province and extending Roman power over the tribes east of the Black Sea. The Roman senate now voted Trajan the title of Optimus for his accomplishment, which he adopted into his official nomenclature from now on.
Trajan left either Elegeia or Artaxata in late spring, 115. From there the Romans marched through the central Taurus Mountains, consolidating the land between the Euphrates and the upper Tigris and fortifying the region with permanent garrisons along the way. They practiced drills as they marched since there was no resistance and arrived in the target zone by midsummer. Meanwhile Lusius Quietus had swung down from Lake Van into the Parthian client kingdom of Adiabene, defeating its king, Mebarsapes and advancing into the eastern part of Mesopotamia. Trajan was skirting Osrhoene now and attacked the western part of the territory. Batnae was taken quickly as punishment for its king not offering fealty to the emperor, followed by Nisibis, which became the new headquarters for the year. Mebarsapes retreated beyond the Tigris while Abgar VII of Osrhoene did homage to Trajan, who made his kingdom an autonomous protectorate. The kings of the Scenite Arabs and Gordyene then tried to negotiate with the emperor, but he refused to hear any offers unless they did homage to him in person. He then marched into Adiabene again to meet with Lusius Quietus, who peacefully occupied a swatch of territory from Singara possibly to Dura Europos. With this done Trajan created a new province from his year's conquests, called Mesopotamia, and announced it and the formation of the province of Armenia in a formal letter (called a laureled letter) to the senate. He now received the title Parthicus and wintered in Antioch after leaving instructions with Edessa for the construction of pontoon bridges to cross the Tigris next campaign season.
Crossing the Tigris, Sacking Ctesiphon
Over the winter a devastating earthquake hit Antioch, in which the emperor nearly lost his life. As the new campaign season began Trajan made his way to the Tigris for another campaign. At this point the Romans could have conceivably declared victory on the basis of their existing gains and gone home. But a combination of a lack of serious Parthian resistance and perhaps a desire to advance the border to the edges of the Iranian plateau egged him on. Firstly Adiabene had to be dealt with, which meant crossing the Tigris. The crossing was contested fiercely by the native Adiabenians, but the Romans eventually crossed thanks to the covering fire of mixed teams of Legionaries and archers backed up by missile engines on the pontoons. Possibly the crossing occurred near modern Cizre and from there Lusius Quietus swept into Adiabene. Three divisions were dispatched. One marching south through Adiabene captured Ninus (Nineveh), the capital of Arbela, Guagamela, and Adenystrae. This completed the formal occupation of the kingdom, and Mebarsapes fled to the Parthian summer capital of Ecbatana with his family for refuge. The second division meanwhile was advancing down the western bank of the Tigris and took Babylon. Trajan personally led a third division to Dura Europos and marched south along the Euphrates with a fleet of ships on the river. Surviving itineraries imply the emperor was following the route of Xenophon's Ten Thousand from the 4th Century BC on his journey while also visiting the asphalt wells at Diacira, used in building the walls of Babylon. Trajan pressed onwards and built a tribunal at Ozogardana, bringing him within striking range of Ctesiphon, the Parthian capital.
Meanwhile the river fleet had sailed onwards to the Naharmalcha (Royal River), the Parthian canal south of Ctesiphon that linked the Tigris and Euphrates. The emperor had no intent of using it for his assault on the capital. Instead he proposed to cut his own canal at a site called Sippar where the two rivers flowed close to each other and use this to cross the Tigris. But since the Euphrates flowed at a slightly higher elevation the risk of flooding believed too great. Instead Trajan dragged his river fleet overland with capstans and rollers and attacked Seleucia, the city opposite Ctesiphon. That done he put his fleet to water and crossed over to take the capital. The Parthians gave no resistance and the Romans captured his great golden throne and his daughter whom left behind. The fall of Ctesiphon marked the end of the third year's campaign and the war. Trajan now asserted his conquests justified the title Parthicus. After a review of the conquered territories he embarked on his flagship and sailed down the Tigris to modern Basra (then called Spasinu Charax) in the client kingdom of Mesene and looked out on the Indian Ocean. There Trajan watched a merchant ship sailing for India and publicly lamented being too old to follow Alexander the Great's path to India. A second laureled letter was sent to the senate and a statue erected to mark the limits of his advance.
The Parthians Respond
Despite Roman successes, the Parthian army remained intact. No set piece battles had been fought yet and the great king had retreated behind the Zagros Mountains at the beginning of the war, instructing his troops to carry out a scorched-earth policy as they followed him. But the civil war had continued regardless until the fall of Ctesiphon. The different factions, now shocked by Rome's achievements, agreed to unite under Osrow for the immediate emergency. A Prince Sanatruk (Sanatruces), another of Osrow's nephews, was nominated for the Armenian throne and charged with starting an insurgency against the Romans. Trajan, meanwhile, was in Babylon for personal reasons when news reached him that Parthian armies had arrived on scene and his garrisons evicted and killed all across the new provinces. Sanatruk had timed his revolt to coincide with the moment the Romans were most overextended, before they could consolidate their gains. Before long Osrhoene had switched sides and Seleucia rose in revolt as well, putting Trajan himself under threat.
The emperor reacted swiftly with three divisions. The first, under Appius Maximus Santra, was defeated in Mesopotamia and its commander slain by Sanatruk's forces. The second, under the reliable Lusius Quietus, was active in the north retaking Nisibis, Edessa, and a number of other cities in the region. Sacking and burning them all as punishment for the revolt. The third, under the joint command of Erucius Clarus and Julius Alexander retook Seleucia and burned it before Trajan joined them to confront and defeat Sanatruk's main force on the field near Ctesiphon. The Parthian prince perished soon after in suspicious circumstances. The revolt was seemingly crushed, but a second Parthian army was still active in Armenia under Sanatruk's son Valaksh. The danger posed by this army is well attested by the speed with which Trajan accepted Valakh's offer of an armistice in return for a portion of Armenia. The emperor then returned to the Parthian capital and crowned Osrow's son Parthamaspates as the new ruler of Parthia on Rome's behalf, for which the new king paid him homage. Trajan then rushed north to retake the vital fortress of Hatra, which controlled the Nisibis-Ctesiphon road and was key to Roman control over the Tigris. But the environment was inhospitable to the besiegers, lacking water, timber, and fresh fodder. Illness soon set in, but the emperor was determined to take the fortress. Finally, he managed to breach the walls with the imperial horse guards (the equites singulares Augusti) but was driven back and almost lost his life. Winter soon followed, and the onset of winter storms forced Trajan to admit defeat and retreat to Antioch, where he fell ill soon after.
The Jewish Revolt and the Limits of Ambition
At the same time a massive revolt in the Jewish communities of the Roman Empire in Cyrenaica, Egypt, and Cyprus called for the emperor's attention. The revolt had started in early 115, gaining intensity with the Mesopotamian Jews joining in over the past year. Trajan reacted with the appointment of Marcius Turbo in early 117. More disturbances followed in Mauretania and Britain and the Sarmatian Roxolani and Iazyges were threatening war again. Closer to home the Jewish homeland of Judaea was showing signs of joining the revolt and Parthamaspates was engaged in civil war. The emperor was forced to abandon his plans for a new campaign for 117 and return to Rome to celebrate his victories.
Hadrian was left in command of the eastern armies as Trajan departed that summer. He died soon after in August at Selinus and his cousin succeeded him in short order a few days later. The new emperor moved swiftly to renounce all of Rome's gains east of the Euphrates, with Dura Europos being the last by the beginning of October that year. Parthamaspates soon lost his throne, to be compensated with Osrhoene by Hadrian, leaving the Romans with little to show for such a militarily spectacular war.