Trajan’s Dacian War

Trajan was one of Rome’s most successful emperors. Discover the story of his most famous conquest: the wars against Dacia.

Aug 9, 2022By Kieren Johns, PhD Classics & Ancient History

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Priscianus Caesariensis was a grammarian from the North African city of Caesarea. During the sixth century CE, he produced his most famous work, the Institutes of Grammar, which was the standard textbook for Latin grammar in medieval Europe. The life and work of a grammarian may seem an unusual place to begin this tale of Roman emperors and imperial conquest, but Priscianus’ Institututes offers a tantalizing glimpse into a text otherwise lost to time… To help his reader understand a particular grammatical rule, Priscian writes: inde Berzobim deinde Aizi, or, “We then advanced to Berzobim, next to Aizi”. Specifically, Priscian’s grammar lesson is citing a sentence from the emperor Trajan’s now lost Dacica. Sometimes also known as de bello Dacico, this was an autobiographical account of how Trajan staged the conquest of Dacia.


Written in a style similar to Julius Caesar’s de bello Gallico, the now-lost text is sure to have provided a whole range of fascinating insights, not only into the wars and the Dacian people, but also into the character of Trajan himself. Today, history remembers him as the optimus princeps, a reputation he forged after a successful reign spanning almost two decades (98 to 117 CE). Perhaps his most enduring success was the conquest of Dacia and the final great expansion of the Roman Empire. This is the story of Trajan’s Dacian Wars.


1. Prelude: The Dacians, Domitian’s death, and Trajan’s Rise

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Portrait bust of Domitian (left), c. 90 CE, via Toledo Museum of Art; and portrait bust of Nerva (right), c. 96-98 CE, via J. Paul Getty Museum


In 96 CE, the final Flavian emperor, Domitian, was murdered in his palatial residence atop Rome’s Palatine hill. The plot that killed him had clearly been brewing for some time, probably a result of his unpopularity with the senate in Rome. His successor, Marcus Cocceius Nerva, was quickly installed as the next emperor. However, there were problems. First and foremost, he was old and did not have an heir. Continuity was key in imperial politics, so this did not bode well for Nerva. Worse still, Domitian’s unpopularity did not extend to the Roman armies. The soldiers were furious that their emperor had been slain. The situation became critical in 97 CE when members of the praetorian guard took Nerva hostage. To allay the soldiers’ concerns, Nerva chose Marcus Ulpius Traianus as his successor. The governor of Germania at the time, he had a reputation as a formidable soldier.


It also did not help that Domitian’s reign had led to the emergence of a new military threat to the north. In 84-85 CE, the Dacians had crossed the Danube from their homeland (roughly equivalent with modern Romania) and ransacked the province of Moesia. Led by their king, Decebalus, they even had the temerity to kill the provincial governor. Although Domitian’s retaliation had been initially successful, it remained inconclusive. It would be left to Nerva’s successor to resolve the Dacian issue…

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2. Discovering the Dacians

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Portrait of a Dacian, of the type from Trajan’s Forum, 120-130 CE, via Museo del Prado


The kingdom of Dacia was relatively young by the time of Trajan’s accession in 98 CE. It had been founded in the first half of the first century BCE, after the king Burebistas had conquered and united a number of other regions in the area. In doing so, he also forged close relationships with the Greek colonies on the coast of the Black Sea. It was also Burebistas who established the city of Sarmizegetusa as the capital city of the Dacians. After Burebistas was murdered (coincidentally in the same year as Julius Caesar: 44 BCE), the Dacian kingdom fractured. Unity would not be restored until the rise of Decebalus late in the first century CE.


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Dacians assaulting Roman fortress (scene from Trajan’s Column), by Pietro Santi Bartoli, 1672, via Royal Academy Collection


Culturally, getting to grips with the Dacians is more challenging. This is mainly because so much of what historians know is filtered through Greco-Roman lenses. To many ancient authors, such as Pliny the Elder, Strabo, and Cassius Dio, the Dacians were considered broadly as Thracians and to speak the same language. The close connections between the Dacians and the Greco-Roman communities they interacted with can be seen in their culture, especially coinage which consciously imitated both Hellenistic-Macedonian coinage and later the denarii of the Roman Republic.


3. The First Dacian War, 101-102 CE

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Cuirass Statue of Emperor Trajan, after 103 CE, via Harvard Art Museum


After securing peace with Domitian in 89 CE, the Dacian King – Decebalus – was viewed as a rex amicus (a king friendly to Rome). However, the peace was seemingly weighed in favor of the Dacians, which irked the Romans. Worse still, the empire was suffering from shortages of metals – both gold (affecting the currency) and iron and copper (for arms and armor) – which needed to be addressed as a matter of priority. Fortunately for the Romans, Dacia was rich in these precious raw materials, and the belligerence of Decebalus and the lopsided Domitianic treaty meant that conflict could be justified. This is the casus belli given by Cassius Dio, writing some time after the war, but who nevertheless remains the most complete account of Trajan’s campaign.


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Emperor Trajan and the province of Dacia, personified, kneeling before him, from the Arch of Trajan, Benevento, via Carole Raddato/Flickr


Trajan’s Dacian War actually occurred in two stages. The first war lasted from 101-102 CE. The Romans advanced into Dacia from the city of Viminacium. The city had been the base for the Roman invasion of Dacian territory during Domitian’s war previously. After crossing the Danube River and marching into the heart of Dacia, Trajan and the Roman forces decisively defeated a Dacian army at the Second Battle of Tapae. With winter looming, Trajan hesitated in the advance on Sarmizegetusa, the Dacian capital. Decebalus took advantage of the pause and marched to assault the Roman province of Moesia.


A first battle, near the future city of Nicopolis ad Istrum, was a tentative Roman victory. The second engagement, the Battle of Adamclisi, was a hard-fought Roman victory. Decebalus, seeing that defeat was inevitable, requested a truce. Trajan agreed, under the provision that the Dacians yield territory held by the Romans, as well as the weapons and materials they had received after the treaty of 89 CE. Although Decebalus acquiesced to the terms, this would only be temporary…


4. The Second Dacian War, 105-106 CE

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Copper sestertius of Trajan, with a reverse depiction of the personified Tiber, standing left, pushing personified Dacia to the ground, with the legend S P Q R OPTIMO PRINCIPI S C, minted 103-111 CE, via British Museum


Decebalus’ acceptance of Trajan’s terms did not last long, and soon he was whipping up support among Dacian tribes to attack Roman settlements across the Danube. By 105 CE, Trajan had made the decision to march on Dacia again and bring the problematic kingdom to heel decisively. The start of the war was marked by one of the great Roman engineering feats. Trajan had his architect, Apollodorus of Damascus, construct a permanent bridge across the Danube at Drobeta. Apollodorus, who would later fall foul of Hadrian’s own architectural pretensions, was responsible for constructing what would be the largest arch bridge for more than a millennium!


Now lost, some piers that once supported the bridge still remain. More importantly for Trajan, the bridge allowed his legions to quickly cross into Dacian territory and begin to march northwards. By the summer of 106 CE, the Dacian capital, Sarmizegetusa, was under attack.


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The suicide of the Dacian King Decebalus to avoid capture by the victorious Romans, Detail from the relief on Trajan’s Column, via Wikipedia


The city initially resisted the Roman attack. However, it could not endure forever. The Romans cut Sarmizegetusa’s water supply, and the city began to starve. When it eventually fell to the Romans, the Dacian capital was razed to the ground. Decebalus and a number of other Dacian defenders attempted to flee, but they could not outrun the Roman cavalry in hot pursuit. The Dacian King, faced with the ignoble end of being paraded in Rome and executed as part of Trajan’s triumph, decided to commit suicide. The Column of Trajan would immortalize this scene for posterity; on the brink of capture, Decebalus continues to frustrate the Romans, falling on his sword just before he falls into the hands of the pursuing cavalry.


The war continued after, but this was largely a case of the Romans mopping up the last pockets of Dacian resistance, including at the final, decisive battle at Porolissum. Cassius Dio’s history records a final insult to Decebalus’ legacy: the Roman discovery of his treasure. Its final hiding place in the Sargesia River was revealed to them by a treacherous associate of the Dacian King, Bicilis.


5. The Spoils of War

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Cuirassed portrait of Trajan, bronze, ca. 107-108 CE, via Digital Museum


Despite being perhaps the defining events of Trajan’s reign, the conquest of Dacia was a remarkably rapid affair. Heavy Roman losses across the Danube in both instances could not mask the fact that the Dacians were roundly defeated in two year-long campaigns in short succession. Regardless, the final victory in 106 CE was marked with jubilant scenes in Rome. Trajan himself announced 123 days of celebrations throughout the empire, which included enormous gladiatorial shows and beast hunts: Cassius Dio described some eleven thousand animals being slain, as well as ten thousand gladiators. Dacia was added to the empire as a province and guarded by two legions – legio XIII Gemina and legio V Macedonia – who were posted there permanently to prevent future insurrections from the north.


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Gold Aureus of Trajan, with reverse view of Basilica Ulpia in the Forum of Trajan with trophies and quadriga statuary, 112-117 CE, via British Museum


More significantly for the Roman Empire, however, was the sudden influx of enormous wealth as a result of the conquest of Dacia. The region was rich in metals, especially gold. It has been estimated that some 700 million denarii per year were contributed to the Roman economy as a result of the Dacian mines. The effect on the empire was profound. New campaigns could be funded, defenses improved, while the cities in the empire would benefit from expansion and ornamentation. Nevertheless, it is a truth of war that every triumph hides tragedy. Alongside the material cost of the war, a huge number of Dacians were taken from their homeland and sold into slavery.


6. Commemorating Trajan’s Triumph: Monuments of Victory

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Speculum Romanae Mangificentiae: Trajan’s Column, by Giovanni Ambrogio Brambilla / Claudio Duchetti, 1581-1586, via Metropolitan Museum


Several of Trajan’s more notable architectural legacies can be directly connected to the Dacian Wars and the booty that the emperor was able to extract from the conquered region. Trajan’s power was stamped all over the urban center of Rome. The extensive list of structures he gave to the city includes the thermae (baths) on the Oppian Hill and the Mercatus Traiani (the Markets of Trajan). However, his greatest legacy was the Forum of Trajan. Inaugurated in 112 CE, it was sandwiched between the Forum Romanum and the Forum of Augustus (which it dwarfed). It was, and remained, a “construction unique under the heavens”, according to the historian Ammianus Marcellinus who visited in the 4th century CE.


The forum reveled in Trajan’s military successes, and statues of captured Dacians were incorporated as part of the decoration as a permanent reminder. To the north of the Forum, there was also Trajan’s Column. This incredible monument featured a helical frieze that wrapped around the extent of the column’s considerable height. The spiraling frieze narrated the Dacian campaign to the viewer.


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View of the Tropaeum Traiani, via Wikipedia


Trajan’s victory was also commemorated in Dacia itself. The Romans had established a colony of veterans at Civitas Tropaensium (modern Adamclisi). In 109 CE, Trajan erected a monument there, now known as the Tropaeum Traini. It commemorated the Dacian campaigns generally, but also the Battle of Adamclisi which had taken place during the first war specifically. The tropaeum replaced an altar that had been erected on the same site, on which the names of over 3,000 legionaries who died in the battle had been recorded. The monument was dedicated to the god Mars Ultor (‘Avenging Mars’), who was also honored in Rome with a temple in the Forum of Augustus.


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Metope XX from the Tropaeum Trainai: Roman legionary in combat with a Dacian falxman and an injured Germanic warrior, via Wikipedia


As a work of art, the Tropaeum Traiani lacks the aesthetic finesse that is displayed on the relief on Trajan’s Column in Rome. However, it was still elaborately decorated. It was surmounted by a tropaeum. These were T-shaped ‘trophies’ made of captured weapons and arms. They were common motifs in Roman art, used to communicate military superiority. The monument was also decorated with fifty-four metopes. A metope is a rectangular relief that features as part of a classical Doric frieze (the most famous examples being those from the Parthenon in Athens). The Adamclisi metopes show scenes of Trajan’s Dacian war. The Tropaeum Traini, as it appears today, is a modern restoration undertaken in 1977. Nevertheless, the scale of the structure provides an enduring indication as to the importance the Roman people attributed to Trajan’s Dacian campaigns.


7. Modern Legacies: Trajan and Decebalus in Modern Romania

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Statue of the Emperor Trajan and the She-Wolf, by Vasile Gorduz, 2012, via Wikipedia


The expansion of the Roman Empire across much of the European continent and beyond has resulted in numerous states using Roman antiquity in their nationalist myths. Figures from the ancient past loom large in the national consciousness, including both the Romans and their native rivals, creating complex historical narratives of national identity. In France, for example, Julius Caesar’s great Gallic adversary, Vercingetorix, is immortalized in statues, much as Boudicca, queen of the Iceni, is in Britain.


In modern Romania, which occupies much of the same territory as the ancient Dacians, the relationship with Roman antiquity is similarly complex. On the one hand, the Romanian state has celebrated its Roman heritage. Frescos created by Costin Petrescu in 1888 in the Romanian Athenaeum in Bucharest show the Romans bringing civilization to the Dacians, while the relationship between the two states was clear from the pairing of Trajan and Decebalus, ancient enemies, on modern Romanian money. As recently as 2012, the mayor of Bucharest unveiled a statue by Vasile Gorduz that showed this relationship continued unabated. Depicting a nude Trajan, the Roman emperor cradles a creature combining a Dacian Draco (Dragon) and the Roman She-wolf.


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Side view of Iosif Constantin Drăgan’s Decelabus Rex, the inscription below the Dacian King’s portrait reads Decebalus Rex Dragan Fecit (‘King Decebalus, Dragan did this’), via Wikipedia


However, the Romans are far from having things their own way. Although the Romanian diplomat, Raoul Bossy, may have declared that “the name itself is a pedigree: Romania comes from Rome” in the 1950s, Decebalus has been just as important in Romania’s nationalist mythmaking. The fallen Dacian king has been commemorated throughout Romania, including in an equestrian statue that was erected in Deva in 1978, which marked a shift towards more Romanian, rather than Roman, notions of national identity.


Most famously, there is Iosif Constantin Drăgan’s Decelabus Rex. Carved into the cliffs overlooking the Danube, this colossal portrait of Decebalus is a material manifestation of the belief that Dacia was the cradle of Romanian civilization. Viewers will note, however, that beneath the portrait, Decebalus is identified in an enormous Latin inscription.


Thanks in part to the continued vivacity of these nationalist debates, the argument over whether Romania is a product of the Dacians, the Romans, or a combination, it is clear that Trajan’s campaigns of conquest in Dacia will continue to be relevant, and fascinating, for many years to come.

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By Kieren JohnsPhD Classics & Ancient HistoryKieren is a UK-based independent researcher with a PhD in Classics and Ancient History. His thesis explore the representation of imperial status during the reigns of the Severan emperors. He is passionate about sharing his interest in the ancient world. He is currently writing his first book.