June AD 123 – Hadrian returns to the East and inspects the frontiers of northern Syria and Cappadocia (#Hadrian1900)

After spending the winter of AD 122/3 in Tarraco (see here), Hadrian left Spain and set sail for Antioch and the Euphrates frontier, probably reaching his destination in June 123. According to a drastically abbreviated passage in the Historia Augusta, the Emperor aimed to meet the Parthian king (or receive Parthian envoys), indicating a renewal of hostilities between the Parthians and the Romans.

“The war with the Parthians had not at that time advanced beyond the preparatory stage, and Hadrian checked it by a personal conference.” SHA, Hadr. 12.8

Unfortunately, the journey from Spain to Syrian Antioch is very poorly documented. After inspecting the western provinces, the Historia Augusta abruptly telescopes Hadrian to Antioch. Nothing is said about how he got there. In all probability, he journeyed by sea along the North African coast, with possible stops in Carthage, Cyrenaica, on the island of Crete and Cyprus, before landing at the port of Antioch at Seleucia Pieria.

A stay in Carthage in Africa proconsularis is a real possibility as extensive road-building on the Carthage-Theveste road (via a Karthagine Thevestem) was undertaken around this time. Milestones found between Carthage (Tunis, Tunisia) and Theveste (Tébessa, Algeria) state that Hadrian had the Carthage-Theveste road paved by the Third Augustan Legion, under the supervision of Publius Metilius Secundus, who was the imperial legatus pro praetore and commander of Legio III Augusta during Hadrian’s 5th tribunicia potestas (AD 121).

Metilius probably started building the 258-kilometre-long road and related structures (including at least 37 bridges) one and a half years earlier, during Hadrian’s 5th tribunicia potestas in 121/2 (de Vos Raaijmakers, 2019). On July 1 of 123, Publius Metilius Secundus was replaced by Sextus Julius Major, as mentioned on a bridge inscription (AE 1995, 1652) over the Wadi Naguess near Ammaedara at the 164th mile (Grira, 2016), also built by the 3rd Legion. Sextus Julius Major would begin building the Via Nova Rusicadensis in 125/6 (CIL VIII, 10296) in the neighbouring province of Numidia.

Another plausible stay on the route eastwards is Cyrenaica, the province administered jointly with Crete (Birley, 1997), which had suffered widespread destruction during the great Jewish revolt in AD 115/7. Restoration of the territory of Cyrenaica began under Trajan, but Hadrian was primarily responsible for the rebirth of Cyrene. He later brought in new settlers and founded a new city named Hadrianopolis, probably hoping it would revive the province (read here). Hadrian and his entourage could sail across to Crete from the port of Cyrene and then continue north to Cyprus. The governor of the province of Cyprus at the time was Gaius Calpurnius Flaccus (IGR III, 991), a Spaniard from Tarraco and the son of Hadrian’s host at Tarraco (Birley, 1997-Alföldy, 1981).

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Hadrian probably arrived in the Syrian capital in June 123, as the chronicler John Malalas (11.278) reports that Hadrian founded a “festival of the strings” at Antioch’s suburb Daphne named Hadrianeion, to be held there every June 23. Antioch, where he had been hailed emperor six years previously, had not fully recovered from the devastating earthquake that struck the Orontes Valley on 13 December AD 115 (see here) and still bore the scars of the disaster. Antioch received imperial largesse on an unprecedented scale. Malalas adds that Hadrian had public baths and an aqueduct constructed to help the city, while the Suda, the Byzantine encyclopedia, speaks of a”small elegant temple for the deification and honour of his father Trajan” (Jo. Ant, fr. 206).

Hadrian had presumably come to Antioch to have a peace summit with the ruler of Parthia, so he proceeded to the eastern frontier. Birley notes, “Traditionally, these diplomatic encounters took place on the Euphrates, with each side coming across in turn for dinner.” The Syrian army was indeed already there in force. It was composed of the legions II Traiana and III Cyrenaica and their auxiliaries under the command of Tiberius Claudius Quartinus, who was governor of Tarraconensis and dispatched from there by Hadrian to accompany the military expedition (CIL XVI, 4473).

The Eastern frontier was, under Trajan, the theatre of Rome’s last significant wave of territorial expansion, but with Hadrian’s accession in 117, the Parthian wars of his predecessor came to an end. Hadrian withdrew all Roman forces beyond the Euphrates, ordering the new territorial acquisitions to be returned to the Parthians and installing Parthamaspates as King of Edessa (SHA, Hadr. 21.10), who would then rule until 123, when Ma’nu VII of the Abgarid dynasty was installed. The use of the term conloquium in the Historia Augusta suggests a personal meeting, but no details about the dispute have survived, and we don’t even know which Parthian king Hadrian met. It could have been Vologases or Osroes, as more than one king was occupying the throne of Parthia at the time.

According to Birley, the Parthian king Hadrian met was Osroes, who pressed for the return of his captive daughter. Elsewhere, the HA (13.8) indicates that Hadrian returned the daughter of Osroes, whom Trajan had taken captive in Ctesiphon in 116, and promised to restore the golden throne of the Parthian kings, which had remained in Roman hands. Hadrian returned the daughter of Osroes in 128/9 but kept the royal throne as Antoninus Pius refused a later request from Osroes to return it (SHA Ant. Pius 9.7).

“To petty rulers and kings he made offers of friendship, and even to Osdroes (Osrhoes),​ king of the Parthians. To him he also restored his daughter, who had been captured by Trajan, and promised to return the throne captured at the same time.”​ SHA, Hadr. 13.8

The HA is the only source claiming a personal meeting with the Parthian ruler or his envoys. Dio and all the other sources do not mention any quarrel on the Parthian border during Hadrian’s reign, and no other emperor appeared in person at such a summit. In the 1st century, the emperor had always been represented by a deputy, as Augustus by Tiberius in 20 BC, Tiberius by Germanicus in AD 18, and Nero by Corbulo in AD 63. In 116, Trajan met envoys from Osroes at Athens, not the king himself. Hadrian may not have met the Parthian king in person either (Doležal, 2017).

However this may be, the Parthians maintained peace during Hadrian’s reign, and Armenia, too, remained peaceful under the Arsacid princes. It would be another thirty-eight years before Parthian troops marched into Roman Syria and threatened to take over Armenia and Upper Mesopotamia.

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Following the summit, Hadrian probably remained on the frontier, heading northwards into the valley of the Upper Euphrates to reorganise the defence of the borders in this region as he had just done in the West. Our sources don’t tell us about Hadrian’s whereabouts along the Eastern frontier. The HA says nothing further and passes at once to his return to Rome from Asia and Greece (13.1), making it “the most obscure portion in all the journeying” (Syme, 1988).

At the time of Hadrian’s visit, the defensive system of the Euphrates frontier was supported by four legions and by a large and permanent auxiliary army guarding crossings and vulnerable points. Two legions lay in Syria facing Parthia, Legio IIII Scythica at Seleucia/Zeugma (Belkis) and Legio XVI Flavia Firma at Samosata (Samsat), the capital of Commagene, and two in Cappadocia to the north opposite Armenia, Legio XII Fulminata at Melitene (Eski Malatya) and Legio XV Apollinaris at Satala (Sadak). The main military road, which ran along the eastern border of Cappadocia, connected Trapezus (modern-day Trabzon) with the legionary and auxiliary encampments. The limes road and proximity of the legions would have allowed the quick movement of troops down the river.

Vespasian’s eastern frontier line began at Zeugma in northern Syria, passed through Commagene, Cappadocia and Armenia Minor, crossed the Pontic Mountains, and ended on the Black Sea shore at Trapezus, the headquarters of the classis Pontica. The limes continued eastward along the Pontic shores of the Black Sea up to Apsarus (Gonio), just across the modern Georgian border.

During Trajan’s eastern campaigns (AD 114-117), Hadrian, headquartered in Antioch as governor of Syria, was entrusted with assembling a substantial army of 80,000 legionaries and auxiliaries for the upcoming campaigns; he was therefore familiar with the area. He may have also taken the field as a member of Trajan’s entourage and witnessed the Optimus Princeps receiving Anchialus, king of the Heniochi and Machelones (Dio, 68.19.2), at the legionary fortress of Satala in AD 114, before advancing eastwards to Elegeia and Artaxata, the Armenian capital. Hadrian later relinquished their country with the other conquests of Trajan east of the Euphrates, and Hadrian “permitted the Armenians to have their own king”, the HA reports (SHA Hadr. 21.11).

With an overall length of approximately 550 km, the Pontic-Cappadocian frontier, extending from northern Syria to the western Caucasus across a remote and desolate region, was among the longest in the Roman Empire, yet also the least archaeologically known in terms of physical remains and epigraphical evidence (Breeze, 2022). However, it was the subject of a unique account by Lucius Flavius Arrianus (c. AD 86/89 – c. after 146/160), better known as Arrian of Nicomedia, the famous biographer of Alexander the Great and governor of Cappadocia, between 131 and 137.

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Hadrian will likely have travelled up the Euphrates, then over the Pontic Alps to the port of Trapezus, along the frontier road that linked all the legionary and auxiliary camps. He will have visited the legionary fortresses established since the reign of Vespasian and surveyed the northern part of the eastern limes in the provinces of Syria and Cappadocia. He may, however, have left the difficult Euphrates route from Melitene and gone northwest to Sebastia (Sivas) and Neocaesarea/Hadrianopolis (Niksar) and then east to Nicopolis/Hadriane and the fortress of Satala (Biley, 1997).

Zeugma and Samosata in Syria would have been the first legionary bases on Hadrian’s route along the Euphrates River. Unfortunately, there is little evidence of the fortresses at those sites, and they have been irretrievably lost to archaeology as they now lie under reservoirs. However, Zeugma yielded roof tiles stamped by Legio IIII Scythica and a single inscription referring to the unit’s signifier (standard bearer) (AE 1908, 00025). In addition, inscriptions carved into the limestone quarry walls, located approximately 35 km upriver from Zeugma, record work by vexillations of the Fourth Legion (AE 2001, 1956). They also constructed three Roman miles of canal, with bridges, to improve water transportation near Antioch (AE 1983, 00927) while under the command of Marcus Ulpius Traianus, the father of the future emperor Trajan and legatus of Syria. At Samosata, at least three inscribed dedications naming the Sixteenth Legion (CIL III, 13609) shed light on the military presence there.

Zeugma owes its name to the important bridge of boats (“pontoon bridge”) that crossed the Euphrates at that location (Zeugma means the ‘link’ or ‘bridge’ in Greek). As early as its founding by Seleucus I Nicator around 300 BC, some form of crossing linked both banks of the Euphrates. Pliny (NH 34.43) mentions an iron chain, apparently still visible in his day, that was shown to visitors as the one used for this purpose by Alexander the Great.

Originally named Seleucia-on-the-Euphrates, the town was conquered by the Romans in 64 BC, who renamed it Zeugma and annexed it to the Kingdom of Commagene as a reward for Antiochus I Theos of Commagene’s support of General Pompey during the conquest. The annexation of Commagene by Germanicus in AD 17, the arrival of Legio IIII Scythica around AD 66, and the final collapse of Commagene in AD 72 formalised Roman control on the west bank of the Euphrates, opening a new era of military and commercial importance for Zeugma.

By the 2nd century AD, Zeugma had become the Empire’s most strategically and economically important eastern frontier city. Its vibrant commercial life made it one of the great cosmopolitan centres, reaching its peak population of about 70,000. As the inhabitants grew wealthier, they began decorating the floors and walls of their villas with frescoes and mosaics.

Zeugma’s splendour declined in the middle of the 3rd century when Sassanid Persia attacked the city. It would remain forgotten for more than 1,700 years. Sporadic excavations began in the 19th and 20th centuries, but the site gained greater attention in 1980, when the Turkish Government announced that it would be flooded by the construction of the Birecik Dam. Archaeologists excavated several residential complexes and unearthed many splendid mosaics in the city. They are now on display at the magnificent Zeugma Mosaic Museum in Gaziantep.

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The fortress at Samosata was also strategically and commercially important, guarding another major crossing point on the Euphrates. Samosata was already a substantial town when Legio XVI Flavia Firma arrived there. The city, founded circa 150 BC, was the royal residence and capital of Commagene, which was incorporated into the province of Syria in AD 72. Coins indicate that Samosata acquired the title of metropolis during the reign of Hadrian. 

Samosata lay in a broad, shallow valley and was divided into two parts: the acropolis, which was a large citadel mound 50 meters above the surrounding plains, and the lower city, spreading over 130 hectares and surrounded by a five-kilometre-long retaining wall constructed in opus reticulatum (a rare construction style in the East). A raised aqueduct, more than 40 km long (now submerged), brought clear water to supply the city’s baths and fountains.

In 1964, Theresa Goell, an American archaeologist best known for directing excavations at Mount Nemrut, was the first to explore the site. She carried out short-term excavations, and Nimet Özgüç conducted salvage excavations between 1978 and 1989, before the mound was completely flooded by the dam construction project. The excavations yielded abundant stamped tiles bearing the Sixteenth Legion’s stamps, an inscribed dedication to Jupiter naming the legion (CIL III 13609), and other documents concerning legionary soldiers (CIL III 06048). The location of the legionary fortress at Samosata remains unknown, but it may have been situated on low ground at the foot of the mound.

Immediately after the founding of Legio XVI Flavia Firma in AD 70, Vespasian moved it to the eastern frontier, initially at Satala and then at Samosata. It participated in Trajan’s campaigns against the Parthians (ILS 2660). After the war in Parthia, Hadrian deployed the legion to Samosata. A vexillation of the Sixteenth Legion constructed the Mithraeum at Dura-Europos in c. AD 210, and fought in Caracalla’s Parthian campaign (216-217). The Sixteenth also built the Severan Bridge over the Chabinas River. After the absorption of the kingdom of Edessa by Caracalla in AD 212/3, Samosata ceased to be a frontier city, and the legion was transferred to Sura, downstream from Samosata.

Several key routes departed from Samosata. One road ran west of the Euphrates to Doliche (near Gaziantep), with three bridges (still extant) crossing the Göksu, Karasu and Merziman rivers, probably all built by vexillationes of the Sixteenth Legion and Fourth Scythica. Roman tombs standing along the Samosata-Doliche road have also been preserved (see here).

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Hadrian would have proceeded northwards along the frontier road, up the Euphrates’ western bank, across the Taurus Mountains and into Cappadocia, the Empire’s north-easternmost province, to reach the legionary fortress of XII Fulminata at Melitene. The defensive system of the highly militarised province of Cappadocia extended to Pontus and the Black Sea, now governed by Gaius Bruttius Praesens, a close friend of Hadrian, endowed with diplomatic talents. Writing to Praesens, Pliny refers to him as a Lucanian (Letters, VII.3). He was twice consul, governed provinces, commanded armies and ended his career as praefectus urbi (urban prefect) of Rome (AE 1950, 66). He was also an Epicurean in his tastes and beliefs, something he shared with Hadrian.

The road from Samosata passed through the fortress at Melitene, entering through the southeast gate and leaving presumably through the north. Writing under Justinian, Procopius (Buildings 3.4.15-19) describes a square fortress with sufficient space for soldiers’ barracks and a depot for their standards. Procopius, referring to it as the metropolis of Lesser Armenia, attributes the development of the civilian town adjacent to the legionary camp to Trajan. The city had an agora with its shops, streets, and stoa, baths, and theatres, all the attributes of a large city. Melitene was also renowned for its fertility, particularly in cultivating fruit trees, producing oil, and making wine.

After service in Syria during the First Jewish–Roman War, culminating in the siege and capture of Jerusalem in AD 70, XII Fulminata (“the Thundering Legion”) was moved by Titus, apparently in some disgrace, from Raphaneae, about 160 km (100 mi) south of Antioch, to Melitene, to control access to southern Armenia and the upper Tigris. It was to remain permanently in Melitene until at least the early 5th century AD (Notitia Dignitatum or. 38.14), but its presence is attested epigraphically only on a single tile found at Arslantepe bearing the legionary stamp.

We have little evidence for the early fortress. The vast surviving walls of Eski Malatya, enclosing an area of c. 55 hectares, probably date to the 6th century AD, following Justinian’s reconstructions. The fortress may lie beneath the ruins, but no study of the site has yet proved conclusively. It may have also been located at a site called Karamildan, 8 km (5 mi) east of Malatya, where a defensive wall surrounds a rectangular area measuring 320 by 300 metres.

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From Melitene, the military road ran north to Dascusa, a cavalry fort, where the Ala II Ulpia Auriana, an auxiliary unit set up by Trajan and transferred to the province of Cappadocia during Trajan’s Parthian War, was stationed (CIL III 6743). Dascusa is listed in the Antonine Itinerary on the route from Satala to Samosata (§ 207) along the bank of the Euphrates, 50 Roman miles from Melitene. Pliny (HN 5.83) gives distances in navigation of the Euphrates, 74 Roman miles above Melitene by ship. The Dascusa military camp was among the earliest garrisons on the Euphrates frontier, established under the reign of Claudius (Mitford, 2021). The cavalry fort was the principal defensive point of this vulnerable and important frontier section. It guarded against any approach from the strategic route leading westwards (Mitford, 2021). The Ala II Ulpia Auriana took part in Arrian’s operations against the Alani in c. 135 (Ektax. 1) and remained in Cappadocia until the end of the 4th century AD.

The area around Dascusa has been submerged since the completion of the Keban Dam in 1975. The road from the south crossed the Karamağara Bridge near Ağın on the Kozluk Stream, an affluent of the Euphrates. The Karamağara Bridge is a notable example of an early pointed-arch bridge, spanning 17 m across the rocky gorge. On its eastern, downstream side, a nearly intact Greek Christian inscription ran along most of its length, citing a passage from the Bible (Psalm 121:8). The inscribed stones of the Karamağara Bridge were rescued and transported to the Elazığ Museum for preservation and further study.

The nearby forts of Ciaca, 32 Roman miles away to the south, and Sabus, 16 Roman miles away in the north, also held mounted cavalry units. These were equites sagittarii, mounted archers well-suited to the high plains, guarding minor crossing points (Mitford, 2021). Ciaca was garrisoned by the ala I Augusta Colonorum, probably raised and stationed in Galatia under Augustus, and appears to have remained on the northeastern frontier throughout its history, also taking part in Arrian’s expeditionary army of c. AD 135 (Arrian, Ekt. 1.).

The cavalry fort of Sabus appears in the Peutinger Table as Saba and in the Notitia Dignitatum as Sabbu (38.14). Timothy Mitford surveyed this fort in the 1960s and reported traces of walls made of small ashlar blocks, forming a square surmounted by a triangle about 275 m long by 195 m wide. The western end of the south wall is preserved to a height of 3.70 m, which may represent the surviving sections of a 1st or 2nd-century fort (Mitford, 2021). No inscriptions or coins are known from this site yet.

The military road continued northwards to Analiba, 44 Roman miles from Sabus, and Zimara, 16 Roman miles further away. Analiba was garrisoned, possibly as early as the mid-2nd century AD, by Cohors IIII Raetorum, which belonged to the army of Moesia Superior until the early 2nd century AD. It was included in the expeditionary forces for Trajan’s Parthian War, as shown by a new military diploma of AD 115 (Chiron 2005: 64). After the war, the unit remained in Cappadocia, as it was part of Arrian’s army and was still listed in the Notitia Dignitatum (38.14). 

Pliny knew Zimara as a reference point in measuring the navigable length of the Euphrates (NH 5.20.1). Relying on information from Domitius Corbulo and Licinius Mucianus, Pliny reports that the upper course of the Euphrates was navigable in places: From Dascusa to Sartona for fifty miles, to Melitene for twenty-four miles and to Elegeia for ten miles. After passing through the Taurus range, the river became navigable again for forty miles to Samosata.

This place, too, will be the most appropriate one for making some mention of the Euphrates. This river rises in Caranitis, a præfecture of Greater Armenia, according to the statement of those who have approached the nearest to its source. Domitius Corbulo says that it rises in Mount Aba; Licinius Mucianus, at the foot of a mountain which he calls Capotes, twelve miles above Zimara, and that at its source, it has the name of Pyxurates.

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Continuing the road per ripam upstream from Zimara in the Antonine Itinerary and the Peutinger Table, the frontier road ran east past the Kemah (Ani-Kamakh) area, the cult centre of the Armenian goddess Anahita, to the plain of modern Erzincan, where it veered north and ran west towards Satata as far as Trapezus and the Black Sea.

Standing 1650 m above sea level, Satala commanded the Euphrates and the north-south road between the river and the Black Sea across the Zigana Pass. It also protected the nearby rich silver and gold mines. Although much ruined, the fortress’s walls can be traced on all sides, confirming its rectangular shape and encompassing an area of 15.7 ha.

Satala was the base of XV Apollinaris in AD 61–c. 73, when it was transferred from Carnuntum in Pannonia in response to the defeat of Caesennius Paetus, and then from 118, when Hadrian moved it from Egypt (Urloiu, 2010). The presence of the XV Apollinaris at Satala was confirmed by abundant tiles bearing the legionary stamp and funerary inscriptions, including one dedicated to Tiberius Julius Martialis, born at Savaria in Pannonia, died at Satala at age 30 after 13 years of military service (AE 1988, 01043 – dated to 118 or 119).

Trajan visited Satala in 114, received client kings from the Pontic coast, and, from there, advanced on Artaxata and descended into Mesopotamia. In 135, Arrian would lead XV Apollinaris and a vexillation of XII Fulminata against the Alani.

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From the Satala fortress, the Emperor would have continued northward along the final stretch of the military road over the high Pontic Mountains to the Euxine (Black Sea) at Trapezus (Trabzon). There were two main ways of crossing the tortured landscape of the Pontic ranges. The shorter but steeper summer route was along the Peutinger route, at 124 Roman miles from Satala, through eight road stations (high-altitude refuges), which the Greek general Xenophon and the Ten Thousand had already used more than five centuries before on their perilous march home. Following the Antonine Itinerary, Trapezus was 135 Roman miles away, passing through the Zigana Pass at 2,032 m (6,667 ft) above sea level and five road stations.

Xenophon recorded in the Anabasis his fighting retreat from Mesopotamia to the Euxeinos Pontos (the Black Sea) across these same mountains and the joyful moment when the Ten Thousand finally saw the sea and shouted, “Thalatta, Thalatta!”, “The Sea, the sea!” (Anabasis 4.7.24). Hadrian undoubtedly followed the high-level frontier road in Xenophon’s footsteps, looked down on the Black Sea and paid homage to the Greek military leader. 

That Hadrian followed the steps of Xenophon is implied by Arrian in a letter to the Emperor written a few years later (Perip. M. Eux., 1.2-3).

We came in the course of our voyage to Trapezus, a Greek city in a maritime situation, a colony from Sinope, as we are informed by Xenophon, the celebrated historian. We surveyed the Euxine sea with the greater pleasure, as we viewed it from the same spot, whence both Xenophon and yourself had formerly observed it.

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Emphasising the Roman military presence within the province of Cappadocia are coins of the exercitus and province types. The reverse of the exercitus type depicts an adlocutio scene with Hadrian, on horseback, addressing three soldiers. In contrast, the reverse of the province coin shows Cappadocia holding a vertical vexillum, highlighting the military importance of the province.

The Emperor’s next stop was Trapezus, and then along the littoral of the Black Sea towards Bithynia.

Sources & references:

• Birley, Anthony R. (1997). Hadrian. The restless emperor, Routledge London New York pp. 151-157.
• Fraser. Trudie E. (2006). Hadrian as Builder and Benefactor in the Western Provinces. BAR International Series 1484.
• Doležal, Stanislav (2017). Did Hadrian ever meet a Parthian king?, in Graecolatina Pragensia, Volume 27 pp. 111-125. https://www.academia.edu/33969517/Did_Hadrian_ever_meet_a_Parthian_king
• Raaijmakers, M. (2019). Twin Roads: the Road Carthage-Theveste and the via nova Rusicadensis; some Observations and Questions. In A. Kolb (Ed.), Roman Roads: New Evidence – New Perspectives (pp. 338-374). Berlin, Boston: De Gruyter. https://doi.org/10.1515/9783110638332-018
• Grira, M. (2016). Notes préliminaires sur les ponts de la voie Carthage-Theveste, in: A. Mrabet (ed.), Le réseau routier dans le Maghreb Antique et Médiéval, Actes du deuxième colloque international, 6- 8 avril 2015 Sousse, Sousse 2016, 103–128. https://www.academia.edu/44058660/La_voie_Carthage_Theveste_dans_la_pertica_de_la_colonia_Falvia_Augusta_Emerita_Ammaedara_Le_dossier_des_milliaires
• Chris Lightfoot, Survey Work at Satala: A Roman Legionary Fortress in North-East Turkey, 1990 – https://www.academia.edu/15031398
• Radu Urloiu, The Movements of Legio XV Apollinaris under Trajan and Hadrian, 2010. https://www.academia.edu/2483838/The_Movements_of_Legio_XV_Apollinaris_under_Trajan_and_Hadrian
• Michael Alexander Speidel, The Development of the Roman Forces in Northeastern Anatolia. New evidence for the history of the exercitus Cappadocicus. In M. A. Speidel, Heer und Herrschaft im Römischen Reich der Hohen Kaiserzeit, Stuttgart 2009, 595-631. https://www.academia.edu/1481105/The_Development_of_the_Roman_Forces_in_Northeastern_Anatolia._New_evidence_for_the_history_of_the_exercitus_Cappadocicus._In_M._A._Speidel_Heer_und_Herrschaft_im_Romischen_Reich_der_Hohen_Kaiserzeit_Stuttgart_2009_595-631
• Mitford, Timothy Bruce (2021). Discovering Rome’s Eastern Frontier – On Foot Through a Vanished World. Oxford University Press.
• T. B. Mitford (1980). Cappadocia and Armenia Minor. Historical Setting of the Limes, in ANRW II/7, 2, Berlin, pp. 1169-1228.
• Michael Alexander Speidel: The Development of the Roman Forces in Northeastern Anatolia. New evidence for the history of the exercitus Cappadocicus. Offprint from: MA Speidel, Army and rule in the Roman Empire of the High Imperial Age, Stuttgart 2009, pp. 595-631, here pp. 602, 604-605, 607 (online).