Sentius the Centurion and Trajan’s Conquest of Adiabene

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The otherwise unknown Sentius wrote his name into the annals of Roman history, specifically Cassius Dio LXVIII.22.3, on the backdrop of the Roman emperor Trajan’s invasion and conquest of much of the Parthian Kingdom in 115. The catalyst of this Trajanic eastern invasion was the decision of the Parthian king, Osroes I, to forcibly establish two of his nephews, first Axidares and then Parthamasiris as king of Armenia without Roman consultation. In the eyes of Trajan, who may have been looking for any excuse to follow the in the footsteps of Alexander the Great, this overturning of over fifty years of Romano-Parthian cooperation over Armenia was a declaration of war. In 114, Trajan had invaded Armenia, rejecting Parthamasiris’ offer to serve as a Roman client and instead annexing Armenia as a Roman province.


The emperor did not stop there. This was not a war with Armenia; this was a war with Parthia. Therefore, in 115, he led a large-scale invasion of Parthian territory. There are some issues with the source material, but this was not just one grand strike through enemy territory in a mad dash for the Parthian capital at Ctesiphon. Perhaps demonstrating his want for more permanent conquest, Trajan had already called together at Antioch many of the client kings of the region, both Roman and Parthian. With his annexation of Armenia and his general demeanour, several of these kings who appeared before Trajan at Antioch recognised that the emperor meant business.

Trajan himself led part of his invasion force through Mesopotamia, incorporating Osrhoëne as a protectorate under Abargus VII by his sheer presence and subduing Batnae and Nisibis, the major cities of the subkingdom of Anthemusia. Having given full demonstration to his aims of conquest, Trajan found that some of those clients who had failed to appear at Antioch were more willing to come to see him. One of those was Mannus, ruler of Scenite Arabs of Mesopotamia. On the surface, this does not seem all that strange, particularly when it seems that Mannus was looking for peace with Trajan because the Parthian king “Osroes was making a campaign against him” (Dio LXVIII.22.1); however, things are not completely straightforward.


Dio also records that Mannus “was ready to withdraw from the parts of Armenia and Mesopotamia that he had captured,” (Dio LXVIII.22.1) suggesting that this Arab leader had taken up arms against not only the Parthian king but also some of the local subkingdoms and even potentially Roman territory in Armenia. This in itself demonstrates that a dichotomy of ‘pro-Parthian’ and ‘pro-Roman’ amongst the smaller kingdoms of the Middle East is too simplistic, with the likes of Mannus being willing and even able to go into business for themselves. Another reason for Trajan to not trust Mannus came in the Arab’s actions in the theatre where Sentius was to make his name – the Assyrian kingdom of Adiabene.


Situated on the right bank of the Tigris and dominated by the Upper and Lower Zab rivers, Adiabene was one of the strongest Parthian client kingdoms; indeed, throughout much of the first century BCE and first century CE, Adiabene appears to have been largely independent from Ctesiphon, making its king, Mebarsapes one of “the most prominent rulers of northern Mesopotamia” (Marciak (2017), 264). Much like Mannus, Mebarsapes may also have been able to expand the territory under his control by 114, including a foothold on the western side of the Tigris (Marciak (2017), 265). Such a loss of direct control by the Parthians in the region may explain not just the opportunistic acquisitiveness of Mannus and Mebarsapes but also of Trajan. These imperial ambitions and the ill-defined status of the region caused by any slackening of Parthian power meant that Adiabene was in the firing line of the legions.

Therefore, while Trajan was subduing Osrhoëne and Anthemusia, a second Roman contingent under the prominent Romano-Berber commander Lusius Quietus had crossed the Tigris and invaded Adiabene. Rather than submit to this invasion, Mebarsapes called for reinforcements from his neighbours: he received a band of auxiliaries from Mannus, a significant reason for Trajan’s suspicion of the Arab ruler (Dio LXVIII.22.2). By the time Mannus had arrived before the emperor seeking peace and forgiveness, his Arab auxiliaries along with the forces of Mebarsapes had already been defeated by Quietus. Such was the extent of his victory that the Romano-Berber general had been able to capture Singara and other cities unopposed. It may even be that seeing the opportunity for a swift conquest of Adiabene provided by Quietus’ defeat of Mebarsapes, Trajan decided to join his general in completing the job in 116 (Dio LXVIII.22.2).

While Quietus was surely capable of finishing the job in Adiabene, having a keen sense of history and perhaps even destiny, Trajan may have felt that a personal injection in the territory where Alexander the Great had defeated the Achaemenid Persian king Darius III at Gaugamela in 331BC would augur well for his own Parthian campaigns. However, Trajan’s crossing into Adiabene seems to have proven trickier than he would have liked. A local force, called ‘barbarians’ by Dio, challenged the emperor’s attempted “bridging the stream opposite the Gordyaean mountains,” (Dio LXVIII.26.2) which does not read like the Tigris or the Zab. It was only when Trajan deployed his specially made “prefabricated pontoons” (Bennett (1997), 201) on wagons and had them assembled, launched and laden with soldiers that the nerve of the ‘barbarians’ broke, allowing for an orderly crossing. Trajan’s building and then deploying of machines may highlight that Quietus had been having some issues with the lack of available timber to bridge rivers and take settlements and ultimately complete the conquest of Adiabene (Dio LXVIII.26.1-3).


With two significant Roman forces now in his territory, Mebarsapes seems to have retreated to another of his more formidable or perhaps more accurately his last fortresses at Adenystrae. The location of this fortress is problematic, with the normal identification with Dunaysir now being rejected on geographical grounds – it cannot have been further west than Nisibis. It may instead be the Ad Herculem listed on the Peutinger Map near Hatra (Dillemann (1962), 285; Marciak (2017), 368). At least one of the Roman forces in Adiabene swept south capturing Nineveh, Arbela and Gaugamela, and given the historical importance of these settlements, it may be that it was Trajan’s column that was forging after the Adiabene king.

Keen to see to the final subjugation of the region as peacefully as possible, Trajan (or Quietus) sent one of his centurions, Sentius, as an envoy to Adenystrae to treat with Mebarsapes. Being chosen for such a task would suggest that Sentius was a well-renowned army officer, and that he either had significant experience in the east or was personally trusted by Trajan, perhaps having served in Dacia. Angered by his defeat by Quietus, Trajan’s invasion and possibly the demands of surrender Sentius now made of him, Mebarsapes broke one of the cardinal rules of international diplomacy: he imprisoned the centurion envoy. The treatment of his envoy will have enraged Trajan and it is no surprise to find the Roman army now descending upon Adenystrae, intent on taking the fortress by force regardless of how difficult a task it may have been.

The emperor need not have worried. Rather than sit on his hands in prison, Sentius had been devising his own plan to undo the defences of Adenystrae. He found help in the form of his fellow prisoners, although the lack of depth record by Dio about this episode makes any attempt to identify these prisoners fraught with speculation. Were they Assyrian political opponents of Mebarsapes? Local thieves or raiders? Or even fellow Romans of Sentius, either part of his embassy or men taken captive from the armies of Trajan or Quietus in the fighting or as they foraged in Adiabene? Whoever they were, they agreed to help Sentius escape.


However, once out of his cell, the centurion stopped short of fleeing the fortress, either because this would draw attention to him or because he had other plans. Perhaps demonstrating the military background of many of the Adenystrae prisoners or the merely his own abilities, Sentius fought or sneaked his way through the fort, killing the garrison commander, who may even have been Mebarsapes himself. He then made his way to the gates and opened them to the approaching Roman army.

bloody_centurion 2copy

It would be easy to view this through Hollywood-tinted glasses: the gates of Adenystrae flung open to reveal a blood-soaked Sentius carrying the head of the Adiabene king and presenting it and the fortress to Trajan. Instead, the likelihood is that Sentius and the prisoners stole through Adenystrae, killed the garrison commander (possibly in his sleep), took over the gatehouse and sent some kind of message to the Romans, before opening the gates to the advance units of Trajan’s army, who secured the fort for the emperor.

It is perhaps also worth noting that in his short record of the episode Dio does not confirm that Sentius survived the ordeal in Adenystrae. Again, it might seem a little too ‘Hollywood’, but it is possible that the brave centurion was mortally wounded attempting to keep control of the gates long enough for Trajanic forces to enter the fortress in sufficient numbers.

If he did survive, one can only imagine the rewards that Trajan bestowed upon him for facilitating the completion of the conquest of Adiabene, now incorporated as the Roman province of Assyria, and opening the road to Hatra and ultimately Ctesiphon.


Bennent, J. Trajan Optimus Princeps: A Life and Times. London (1997)

Dillemann, L. Haute Mesopotamie orientale et pays adjacents. Paris (1962)

Lepper, F.A. Trajan’s Parthian War. Chicago (1948)

Marciak, M. Sophene, Gordyene, and Adiabene: Three Regna Minora of Northern Mesopotamia Between East and West. Leiden (2017)



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