Was Trajan a Serb

Trajan's Bridge over the Danube

also: "Apollodorus Bridge" or "Daker Bridge"

between Drobeta Turnu Severin / Romania and Kostol / Serbia

Reconstruction attempt by the French engineer Duperrex

© Edgar Duperrex (1907)

Surname: Trajan's Bridge
Place: Drobeta Turnu Severin / Kostol
Country: Romania / Serbia
Overbuilt obstacle: Danube
Construction type: Arch bridge
Material: Opus implectum / wood
Construction time: Late 103 - early 105
Involved: Apollodorus of Damascus
Emperor Trajan
Traffic type: Road for wagons and soldiers
Overall length: 1,158 m
Largest span: 35.40 m
Clear height: 44.40 m
Google Earth:

The bridge that Emperor Trajan built around 104 AD. across the Danube, is one of the still famous structures of Roman engineering today, although it has not existed for a long time. Ancient historians spoke of them with the greatest admiration, and yet Emperor Hadrian probably had them destroyed after only two decades.

Marcus Ulpius Traianus (53-117) was already considered a stroke of luck among his contemporaries. During his reign, the Roman Empire reached its greatest expansion. Domestically, he had great buildings erected, was considered to be 'close to the citizen' and sometimes even showed signs of a social political style. He came to power through the prudence of some senators who 'persuaded' the unpopular Emperor Nerva to adopt Trajan shortly before his death.

The Dacian Wars

In terms of foreign policy, Trajan used his reign (98-117) primarily to secure the borders in Germany and Britain and to expand the empire in northeastern Europe. His predecessor Nerva only had a short reign of just over a year, but the clashes with the Dacians had already started under Domitian. In the summer of 85 the Dacians were across the Danube to the south into the Roman province of Moesia in present-day Serbia. At that time the Danube formed the northern border of the Roman Empire. advanced, raided and plundered cities and military camps. Then Domitian marched with strong troops from Rome to the northeastern border and threw the Dacians back across the Danube with great effort.

Bust of the Emperor Trajan.
Vatican Museums / Rome.

© Bernd Nebel

Despite the quick success, it became clear to him that the Dacians were strong, serious opponents who would require his full attention in the future. But since he was militarily bound on several fronts, after a series of skirmishes and mutual assaults, he initially decided on a not entirely advantageous standstill agreement. Domitian's negotiating partner was the Dacian prince Decebal (Roman: 'Decebalus'), who from then on was rewarded his neutrality towards the Romans with a Roman title combined with the payment of regular subsidies.

After Domitian's death and Nerva's brief reign, Trajan was proclaimed emperor and changed Rome's eastern policy in the same year. As the new Princeps, he needed a military success to confirm and raise his reputation among the population. In the peace treaty with the Dacians, which Domitian bought dearly, he recognized a starting point for his own fame. However, he did not rush anything, but approached the whole company very carefully and systematically. First he secured the outer borders of the empire, from which he then withdrew 80,000 legionaries and relocated them to the lower Danube.

With the help of two ship bridges, Trajan penetrated the Danube into the Dacian empire in 101 and achieved a brilliant victory. However, he left Decebal alive, but forced him to humiliate himself in front of him and - now he turned the tables - to pay a war tax to the Romans. However, when Trajan first advanced across the Danube, he made the decision to go further and make the entire Dacian Empire a province of Rome. The enforced peace therefore only lasted four years until Trajan again marched on the Danube.

If Trajan had only wanted to wage another temporary war against the Dacians, he could of course have operated with ship bridges again. His thoughts went further into the future: he saw Dacia not only as a Roman province, but also as a starting point for further conquests in the north. He therefore probably made the decision to build a solid bridge over the Danube immediately after his first Dacian war. Even if the bridge was quite helpful to him in the second Dacian war, one cannot speak of a typical "war bridge" here.

Sources from antiquity and the Middle Ages

Decebal watches from hiding
the course of the struggle against the Romans

Detail of the Trajan Column in Rome

Unfortunately, ancient sources are scarce. The fact that the bridge actually existed is evident from the images on numerous Roman coins from the year 105 onwards. However, the Trajan's Column in Rome, which still exists today, is more realistic in its depiction. This set up Apollodorus of Damascus around 112 in honor of the emperor on the Trajan's forum. Due to the chronological system of the scenes depicted, you can be sure that the building depicted is Trajan's Danube Bridge.

The oldest and therefore most important historical source for the Trajan's Bridge is the Roman historian Cassius Dio (Book 68), who expresses his greatest admiration for this structure. Although it can be assumed that Dio has at least seen the pillars of the bridge with his own eyes, he not only withholds the exact location, but also does not give the name of the builder. And another important question remained unanswered by Dio: what material were the bows made of? Nevertheless, the (incompletely preserved) report by Cassius Dio is without question authentic.

Another historical source is the late Roman historian Prokopius von Caesarea In German publications mostly "Prokop", who was born around the year 500. He names Apollodorus of Damascus as the builder of the bridge and also says that he wrote a written report about the bridge. Based on Prokopius' precise information on the method of manufacture and the exact dimensions of the bridge, science assumes that he must have still had the writing of Apollodurus before him. Today is Apollodor's report from the Danube Bridge. It is also known that Trajan wrote a report on the Dacian Wars, just as Caesar had already done during the Gallic Wars. Unfortunately, this report has not survived either. unfortunately no longer available.

Then there is Johannes Tzetzes, who lived in Constantinople in the middle of the 12th century and also mentions the Trajan's Bridge in a document. Tzetzes refers to Theophilus Patrizius, who is said to have had the work of Apollodorus. In this respect, Tzetzes confirms Apollodorus as the builder of the bridge. It is even more interesting, however, that he contributed further details, as yet unknown, about the type of pillar foundations in the river bed of the Danube.

The site

The exact location at which this historically and technically significant bridge was built was the cause of a vigorous scholarly dispute in the 18th and 19th centuries, because the ancient sources do not provide any clear information about it. Today, however, this dispute can be regarded as decided.

At the beginning of the 18th century, the Italian Count Luigi Ferdinando Marsigli toured Serbia and the lower section of the Danube. He also examined the remains of a bridge near the town of Turnu Severin Today Drobeta Turnu Severin in Romania and was the first to suggest that it must be the famous bridge of Trajan. Joseph Aschbach published an initial confirmation of this theory after the water level in the Danube had reached a historic low in January 1858. An Austrian expedition led by Major Imbrisevic used this opportunity to examine the remains of the bridge in the river bed together with an architect and a local priest. Since their reports showed striking similarities with the historical sources, most of the experts came to the conclusion that the ruins between Turnu Severin and Kladovo (Serbia) must be Trajan's bridge.

Trajan seems to have chosen a place as the location for the bridge, where he had already built one of the two ship bridges during his first Dacian campaign in 101. When Decebal noticed the activities of the Romans, he immediately realized that building a standing bridge could not do any good for him or the Dacer people. He tried, with little success, to persuade the neighboring tribes to attack the Romans together before the bridge was completed.

The first phase of construction

Trajan is said to have been a very talented architect himself and sketched some of his buildings himself. He seems to have been particularly fond of bridge construction, because during his reign there were outstanding examples of the Roman history, which was not exactly poor in bridge construction. He is referred to as the greatest bridge builder of the ancient Jurecka, although he probably preferred to rely on his first-class experts for questions about the foundation or statics. On the Danube, he had a man at his side, Apollodorus of Damascus, who is considered to be one of the most capable builders of ancient times. Nevertheless, Trajan, who stayed in the war zone for a long time, certainly accompanied all steps of the bridge construction intensively.

At normal water level, the Danube is around 1,000 m wide at this point, and this seems to have been the case almost 2,000 years ago. Relatively long ramps were added to the pure width of the water surface because the bridge was supposed to be very high for safety reasons. At that time there was no such bridge anywhere in the world, and certainly not over a deep and water-rich river like the Danube.

The Roman box dam. A double row of logs is inserted vertically into the
Rammed river bed. When the ring is closed, waterproof clay will be in the
Pounded space between the two post spaces. After that, the interior can
be exhausted and you get a dry excavation.

© Stephen J. Ressler

The enormous effort required to build this bridge kept several legions busy for months, presumably primarily auxiliary troops. Auxiliary troops, which mostly consisted of defeated peoples without Roman citizenship. Since they fought with their own weapons and equipment, they are easy to distinguish from Roman legionnaires on historical depictions. Against the background of the techniques available at the time, it is an almost unbelievable achievement that this structure was completed within a year, despite the enormous amount of personnel involved.

Cassius Dio writes about the foundation: "Isn't it the art of marveling at how the work was performed in the swirling water and in the loamy soil, since there was nowhere to drain the river?" Despite this clear statement by Dios, many historians interpreted Procopius' description of the foundation work as if Apollodorus had erected the first six or seven pillars on land and then diverted the river so that the water flowed between the completed arches. The question of whether the river or part of it was diverted during the construction work has not yet been answered with absolute certainty.

But if it had been so, Apollodor would still not have been able to work in a completely dry excavation pit because the groundwater level near the bank corresponds to the water level of the Danube. In addition, he should still have founded 2/3 of the bridge in the open water. Apollodor certainly tried to organize the construction process in such a way that the foundation work took place in the driest season as far as possible. The key to making the pillars in open water was the Roman box dam, which every Roman military engineer had been familiar with since the publication of Vitruvius's textbook (around 25 BC). With a box dam (also coffer dam or coffer dam) you create a dry excavation pit in the middle of a water surface or in the groundwater, in which you can create the foundation and the first layers of the bridge pier.

The Roman box dam

Emperor Trajan makes a sacrifice for the completion of the bridge.
The bridge with its wooden arches can be seen in the background.
Scene of the Trajan Column in Rome. Here a copy in Italica, Spain.

© Bernd Nebel

An interesting detail that is mentioned both in the historical sources and in the reports about the first investigations of the bridge remains in modern times are long oak trunks, which were apparently rammed a little vertically into the river bed in the middle of each foundation. The foundation and the masonry of the pillars were then built around this trunk. Apollodorus probably used these oak trunks as a kind of ranging stick and used these markings as a guide for the further construction of the pillars. The oak trunks were the prerequisite for an absolutely straight course of the bridge. They secured a measurement point in every foundation at which height markings could also be attached and at which all further work steps could be validated horizontally and vertically at any time.

Around the spring of 103 Apollodorus began building the 20 box dams in the river bed. According to Tzetzes, the dimensions of a box dam were about 35.5 m in length and 24 m in width. The construction of the foundations and pillars in a box dam also required waterproof concrete, which was also only available to the Romans. On the foundation floor, which had been freed of mud and sand, not only heavy, hewn stones were used, but other Roman achievements such as opus implectum and opus caementicium were used. The pillars consisted of an outer shell made of bricks.As each Roman legion provided its bricks with its own stamp, we know that at least seven different cohorts were involved in the manufacture of the pillars, which were made with a mixture of crushed stones, sand, water and hydraulic volcanic ash Pozzolan earth was replenished (opus caementicium). Finally, the pillar was clad with precisely hewn stone blocks, which gave the pillars a massive and solid appearance. The piers had pointed breakwaters, which were apparently not only arranged upstream, but (unnecessarily) also on the downstream side.

The 20 river piers had center distances of 170 Roman feet (pes) 1 Roman foot = 29.6 cm This dimension, which Cassius Dio already gives us, has now been confirmed with modern methods such as sonar and underwater archeology. Since the piers were 14.80 m (50 pes) wide, the clear width between the piers was 35.52 m (120 pes). At the time, it was an enormous span for a single bridge span, which you have to imagine 19 times in a row. Smaller stone arches with slimmer pillars were attached to the large arches on both banks behind the portals and reached as far as the start of the ramps. According to the latest research, there were three of these small arches on the south side and only one on the north side.

Another puzzle: the question of materials

Roman coin with the portrait of Emperor Trajan on the obverse and the Danube bridge on the reverse.
The Roman citizens may not have known exactly what the bridge looked like, but they were well aware
that it had to be an extraordinary building.
The text glorifies Trajan as 'the best', a title the Senate had bestowed on him during his lifetime.

Another question that historians of earlier centuries disputed was what material the 19 great arches were made of: stone or wood. Cassius Dio is silent about this, perhaps because the arches were no longer there in his time and he only saw the buttress stumps with his own eyes. The representation on the Trajan Column actually indicates quite clearly wooden arches. But here, too, there were some historians who saw things differently. The already mentioned Aschbach assumed that the arches must have been made of stone for reasons of stability.

This question, too, could only be answered with absolute certainty by the aforementioned Austrian expedition in January 1858. The construction assistant F. Deuster from the shipyard construction management of the Donau-Dampfschifffahrts-Gesellschaft stated in his report: "In the front view of the bridgeheads, holes with a cross-section of 5" to 6 "and a depth of 18" to 2 'are visible in which remains of wood have been found ". These recesses in the abutment were obviously the transition area to the wooden structure. A comparison with the bridge in Alcántara (Spain), which was completed in the same year, shows that the Romans were quite able to build stone arches that were 30 m wide. But why didn't they do it on the Danube?

One must not forget that although there was a long-term strategy behind the construction of the bridge, one was still in a war zone, in the immediate vicinity of a strong enemy. A bridge with a wooden girder made it possible to retreat across the Danube if necessary and burn down the arches behind you. In addition, the production of stone arches takes much longer, because in addition to the exact processing of the stones, a falsework is also required, which is almost as complex as the actually executed wooden arches. The solid construction of the pillars, however, suggests that the stone arches might have been retrofitted later, when the enemy had been defeated and times had calmed down.

How high was the bridge?

After the defeat, Decebal is surrounded by Roman legionaries
and cuts his own throat.

Trajan's Column Rome

Although Cassius Dio gave an unequivocal answer to this, the question of how high the actual roadway was above the water level of the Danube was also long controversial. Dio says the piers of the bridge were 150 pes high, which is 44.40 m. That would be an extraordinary height for a bridge at this time. Some historians therefore do not consider Dio reliable on this point, because the statement appears to them to be exaggerated. But if you ever walk on the Puente de Alcantara, which was built at exactly the same time, the roadway of the Puente de Alcantara is 48 m above the water level of the Tejo. stood in the Spanish Extremadura and looked from there into the Rio Tajo, believes without further ado that this height is realistic. However, the steep banks of the Tagus in Spain determine this height, while the banks on the Danube are very flat. But why should the pillars on the Danube have been so high?

Precisely because the entire superstructure of the bridge was made of wood, i.e. the arches and the deck girders, it was important that the enemies could not easily get to the underside of the bridge from the river in order to start a fire, for example. At this bridge height, such an act of sabotage could not have taken place without greater preparation and certainly not unnoticed by the Romans. Nevertheless, doubts were repeatedly expressed about this enormous bridge height, because the reconstruction of the bridgeheads with the portals and the land pillars did not seem to fit this height either. If the bridge railway had reached the bank at this height, the access ramps would have had to be extremely long.

The Serbian architect Sima Gusic published a new theory in 1996, according to which the height of 44.40 m was only reached in the middle of the bridge and the bridge track sloped from there on both sides of the river. This roof profile can of course neither be substantiated by historical sources, nor does it seem to correspond to the illustration on the Trajan column. However, only one portal and the first five river pillars are depicted on the Trajan Column. The roof profile would only be visible if the center of the bridge could also be seen. However, one should not lightly dismiss this idea, because it could explain the contradictions between the various height indications. Incidentally, old engravings from the bridge in Alcantara show that this too had a roof profile in its original condition. And also the bridge of Alconétar It is sometime between 98 and 138 AD. originated in Spain, which is also attributed to Apollodorus, had a roof profile. The ascent or descent of the Trajan's Bridge would be around 4.5% at the specified heights and would therefore be quite realistic.

Reconstruction by the Serbian architect Sima Gusic with roof profile girders.
The middle arch is more than 44 m high, while the roadway on both banks is only about 19 m above the water level.

© Sima Gusic

The end of the Dacian Empire

A high, stone portal, which was crowned by a kind of triumphal arch, formed the end of the bridge railway on both sides of the river. According to coin finds, it was adorned with sculptures and symbols of victory in antiquity. In 1850, fishermen found a bronze head close to the Serbian bank in the Danube, which allegedly represented Trajan's father and probably belonged to a group of figures that adorned the southern portal.

To secure the bridgeheads, forts were built on both banks of the Danube, in the immediate vicinity of which civilians also settled in the course of time. The town of Turnu Severin developed from the fort on the north side (the Romans called it Drobeta), which today has almost 100,000 inhabitants. The foundation walls of the fort are still preserved. The city's coat of arms contains a symbolic representation of the Trajan's Bridge and the local museum deals with Drobeta's Roman past. The fort on the right side of the Danube was called Pontes. The Serbian community of Kladova (probably derived from Claudia) is located here today.

The Trajan's Bridge with the two forts on a map of Marsigli

Luigi Ferdinando Marsigli (1726)

In the summer of 105 the bridge was so far completed that Trajan and his legions could pull over the new structure to open the second Dacian War. The first Roman coins depicting the Danube bridge were struck in the same year. Trajan's bridge is said to have provided valuable services for supplies or for rapid troop transfers during the war. In the year 106 the enemy was finally defeated, the capital Sarmizegetusa was taken and Dacia was soon a Roman province. Decebal had been persecuted to the last corner of his empire, where he evaded capture by suicide. Decebal's head was sent to the Senate in Rome, which had it publicly displayed in the forum

As Trajan intended, the bridge became an important hub in the settlement and administration of the new province, especially since it was the only bridge over the Danube connecting Dacia and the Empire. Most Romans were familiar with this building because of the illustration on Trajan's Column, but even more because of the numerous coins. The construction of this bridge undoubtedly increased Trajan's fame, but perhaps because of this it was destroyed again after a relatively short time.

The further fate of the bridge

On his way back from the battlefields of the less glorious war against the Parthians, Trajan died in August 117 in Selinus, in what is now Turkey. He was succeeded by Publius Aelius Hadrianus (Hadrian), who was his nephew. With it, there was a shift in the political focus, which was now less geared towards conquering new territories than towards internal consolidation and improving the living conditions of the citizens. With Hadrian the expansion of the Roman Empire ended, stagnation and finally disintegration began.

According to some historians, Hadrian suffered greatly from his predecessor's popularity, especially because at the beginning of his reign Hadrian had four senators executed at the beginning of his reign, all of whom were important military commanders of Trajan. That made him very unpopular with the people. was denied. With regard to Trajan's territorial gains, he was noticeably disinterested and made little effort to integrate the new provinces. He seems to have neglected precisely the areas conquered in the last phase of Trajan's life, to which Dacia belonged.

Above is an arch of the Trajan's Bridge with ten segments to Duperrex. Below four segments, like that
as shown on the Trajan Column. Current research assumes that the variant
with four segments is more likely. However, the three superimposed arches ran
presumably through to the pillars, as with the replica in Drobeta Turnu Severin (above).
In addition, the beams were probably not curved.

According to Cassius Dio, he saw the much-vaunted Danube bridge, known throughout the ancient world, primarily as a possible gateway for barbaric peoples from the north. With this justification, he had the wooden superstructure, i.e. the girder and the arches, burned down so that only the massive pillars protruded from the river bed. According to Cassius Dio, this happened less than two decades after the bridge was built. At Prokop, however, it says: "The bridge was completely destroyed in the course of time by the floods of the Ister Ister is an ancient name for the lower course of the Danube". Some historians see a contradiction in this, but perhaps both apply and Prokop means by complete destruction the razing of the pillars by floods and ice.

The two forts to secure the bridgeheads remained in place for the time being. The province of Dacia with many Romans settled there was then only connected to Rome by ship bridges. In the short reign of Emperor Aurelian (270-275) Dacia was finally abandoned and the border of the empire was moved back to the Danube. Now the ship bridges were also dismantled and the military camp on the northern bank was dismantled. For the remains of the Trajan's Bridge, this may have meant that the pillars in the river bed had lost their value with regard to the still possible repair of the bridge railway.

Scientific processing

Perhaps afterwards the Romans themselves began to regard the remaining pillars only as a quarry for new structures. At least the civilians living on the banks were probably no longer prevented from buying building materials there. After examining the remains of the pillars in 1858, the Austrian major Imbrisevic determined: "It is very regrettable that the residents of Turn Severin appropriated the largest of the solidly hewn stone blocks, supposedly for the lining of a well, and in this way devastated what time and elements still left in this gigantic work of Roman architecture."

For centuries, hardly anyone was interested in the once great building. Occasionally, historians such as Prokopius (around 550) or Tzetzes (around 1150) dealt with the bridge, although these apparently still had ancient sources that are no longer available today. From the 16th century onwards, the question of the exact location came into focus. After Major Imbrisevic examined the remains of the piers and foundations on January 15, 1858 when the water level was very low and Joseph Aschbach published the results, interest among experts increased significantly.

The construction of the wooden arches as they probably looked. Three
parallel rows of bars consisting of four straight individual bars,
form one of the 19 arches. The lengths of the individual bars are shown.

© Mehrotra / Glisic (see sources)

The French engineer Edgar Duperrex examined the remains of the remaining pillars in 1907. As a result of his research, he published the first attempt at reconstruction, which differed significantly from the representation on the Trajan column (see figure at the top). Instead of dividing the arch into four segments, he divided it into ten sections. In addition, he let the three wooden arches, one on top of the other, run through to the pier heads. On the Trajan Column, it is depicted as if the arches run against the struts that form a triangle above the pillar.

Many engineers and historians joined the reconstruction of Duperrex. Since it was considered the most likely structural construction for about 100 years, a number of drawings and models were made according to this system. Such a model exists e.g. in a museum in Drobeta Turnu Severin and there is a scaled-down replica based on this principle on a traffic island in the city. A popular computer animation (see link at the bottom) also builds on the work of Duperrex.

Attempts at reconstruction

In 2013, scientists at Princeton University carried out a comparative analysis of the reconstruction attempts presented to date, in which they subjected the various variants to a structural analysis. The static load-bearing capacity of the systems was considered, but also how effectively they could be established with the technical capabilities of the legionnaires in 104. Except for the detail with the continuous arches, they came to the conclusion that the variant with four arch sections and straight woods is the most likely form of construction. According to the scientists, curved beams were ruled out because they were difficult to manufacture, but also because such timbers are more sensitive to the load case "buckling". The timbers for the arches must of course be significantly longer with four segments than with ten sections. The lengths from 10.67 m to a maximum of 16.15 m. For structural reasons, the cross-section of these timbers should have been approx. 0.45 x 0.45 m. It is known that the Romans were able to make beams of this length and thickness. but can still be realistically produced. The four-part arch would also have had the advantage that it would have required significantly fewer nodes and thus could have been produced much more effectively.

The remains of a river pier on the Romanian side. In the meantime you have an edging
Concrete walls were drawn around the ruins to protect them from the flooding of the Danube.

© TravelBiz Blog

When discussing the actual appearance of the bridge, it should not be overlooked that some of the depictions on Trajan's Column are very detailed. The Danube bridge was especially familiar to the author of the column, because it had built it himself. Apollodorus of Damascus certainly did not miss this opportunity to depict his own building as precisely as possible and in all its splendor.

In 1909, the Romanian Ministry of Water Management ordered the removal of two buttress stumps close to the left bank because they were obstructing navigation. Apparently the two pillars were destroyed without further archaeological investigations. At least the divers deployed discovered the box dams mentioned by Prokopius on the bottom of the Danube.

From 1979 onwards, systematic excavations on the bank and localization of the existing building structure with the help of sonar took place for the first time. From 2003 to 2006 underwater archaeological investigations were carried out. It was found that the remaining building fabric is rapidly disappearing. Only 10 of the original 20 pillars could be detected, which were also already in a very poor condition.

The Danube bridge of Apollodorus of Damascus was an absolute masterpiece against the background of the techniques available at the time. It was by far the longest bridge in the world and the first bridge with a total length of more than a kilometer that was ever built. The span of their arches is also unlikely to have been reached anywhere in the world. The single span was probably exceeded exactly 500 years later by the Anji Bridge in China (year 605; 37 m). The total length - almost 1000 years (!) After the Danube Bridge - was also exceeded by a Chinese bridge, namely the Luoyang Bridge in Quanzhou (year 1059; 1200 m).