History

During the waning years of the Roman Empire, two extraordinary figures rose to rebuild her once great prominence in the world. While their efforts ultimately could not stop the Roman Empire from being lost to the sands of time, their collective work during their reigns would forever transform the empire. Emperors Constantine I and Diocletian would go down in history not only as two savvy political figures, but they also would galvanize and revolutionize the Roman base into pushing back into the Danubian Frontier, a move they thought could essentially restore the empire to its former glory.
    As a quick overview, the Danubian Frontier was the area considered at the time of the Late Roman Empire to be outside the control of the Roman government. Divided by roughly where the Danube itself runs through Europe, with the Late Roman Empire, or Byzantine Empire, occupying the eastern lands centered around the Middle-East while the barbarian-controlled lands being occupied to the west of the Danube. What is important to note is that the Danubian Frontier was once considered part of the Roman Empire, however due to its decline and decay, the Western Roman Empire was unable to survive and fell prey to the barbarian influences of the area (AHRG 1996). The Eastern, Byzantine Empire, though, would outlive its counterpart, and both Constantine and Diocletian viewed the restoration of the Danubian Frontier integral to the restoration of the Empire itself.
    Now, it is one thing to describe the forts and their functions, and quite another to record the massive grandeur they still convey as they still stand today. Pevensey and Portchester, to give examples, are just two of the superb military architectural achievements that defined the Diocletian age. They represented Roman civilization facing a new, threatening world on the frontier, far from the dignified cities where civic life and travel needed no walls. On the frontier, there was a need for castles, and illustrious castles were built. Some were so great in scale that the Saxon people even believed them to be the work of giants. Not only that, their utility is truly underscored by how theyve adapted and readapted into castles for various other figures throughout the ages. There is no more vivid sense of the age of Diocletian and Constantine than through the expression of the military architecture seen dotting the European landscape today (Williams 1997).
    Under Emperor Trajan, the Roman state had reached what is arguable its greatest extent. At this time, Dacia itself was conquered so as to distance the hostile tribes from the ever-dangerous Danube Frontier. Trajan also build numerous important bridges and roads throughout the empire in order to better facilitate trade and military movement from within the empire, greatly increasing the ability of the empire to react to forces on the frontier. It was said, at this height, that the entire Roman Legion could be anywhere within the Roman Empire within two-weeks, a huge accomplishment for the time period. Also, although, Emperor Hadrian, who would succeed Trajan, opposed territorial expansion, he kept the army at full strength, and built fortified boundaries, similar to those found in Britain known thereafter as Hadrians Wall, all between the Rhine and Danube Rivers, further insulated the reigns of Diocletian and Constantine I from assaults against the Danubian Frontiers (AHRG 1996). However, the Danube Frontier would eventually collapse, forever changing the Roman landscape.
    Emperor Diocletian would be the first emperor of the Byzantine Empire to truly push for the Danubian Frontier.  His ascension into power in 284 would prove to be a dynamic changing point for the structure of the Roman ruling organization and consequently their actual military legitimacy in terms of the Empire and its borders. When appointed to power, he single-handedly ended the Crisis of the Third Century, and then he appointed fellow-officer Maximian his Augustus, his senior co-emperor, just a year after he took power. Not only that, he delegated political power over the empire further in 293, appointing Galerius and Constantius as Caesars, and under this Tetrarchy each emperor would rule over a quarter-division of the empire (Roman Colloseum 2008). This division of power allowed the Roman ruling organization at the time, as well as the Roman Caesars at the time, to make quick and decisive decisions regarding military movements.  This type of dynamic and decisive decision-making was instrumental in the successes of the campaigns against Samatian and Danubian tribes during 285-90, the Alamanni in 288, and the usurpers in Egypt around 297-98. In fact, in 299, Diocletian would lead groundbreaking negotiations with Sassanid Persia, a traditional enemy of the Roman Empire, with the result of a lasting and favorable peace (2008).
    To give an example of Diocletians determination with the frontier, he spent the spring of 293, as well as that of 294, campaigning against the Sarmatians and learning how to ensure the security of the borderlands. Diocletian built numerous forts north of the Danube, at Aquincum, Bononia, Ulcisia Vetera, Castra Florentium, Intercisa, and Onagrinum. Again, when examining an ancient map, these forts built a line across the Danube that would later be referred to as the Ripa Sarmatica (Barnes 1976). This afforded himself and his armies a number of safe, defendable structures running the entire length of the Danube, proving it to be a formidable Roman boundary and perfect Roman launching area for an invasion, which is also evidenced with Diocletians victory over Carpi in the same region, and Galerius victory on the Danube. By the end of his reighn, Diocletian had provided the entire length of the Danube with forts, bridgeheads, highways, and walled towns, and sent fifteen or more legions to patrol the region. In fact, an inscription at Sexaginta Prista on the Lower Danube heralded a newfound peace and tranquility for the region, a significant achievement in an area difficult to defend (Petrikovicks 1971). 
    Essentially, Roman methods of fortification over the northwestern portions of the Empire changed significantly during the second and third centuries. What both Diocletian and Constantine recognized were that these changes were due to the increasing insecurity in Dacia, the Danube Frontier. Changes in these methods were more than just a response to the attacks from the frontier. Over both reigns, the Principate sought to standardize the defense of the frontier through the use of fortified cities and other buildings throughout open area of the Danube, so that it could also become a staging ground for further expansion by Roman forces (Thomspon 1956).
    Ultimately, what Diocletian accomplished was nothing short of securing a broken empires borders and purging it of threats to his own power. Diocletian methodically separated and enlarged the empires civil and military services, and through his reorganization of the empires provincial divisions as aforementioned, he basically established the largest and most bureaucratic government the world had ever seen, and at the very least the largest in the history of the empire. He set up new administrative centers for his empire in Nicomedia, Mediolanum, Antioch, and Trier (Petrikovicks 1971). Examined on a map, these locations are found far closer to the empires frontiers, including the Danubian Frontier, than the traditional capital at Rome had originally been. Diocletian not only wanted to shore up the defenses of the Empire on its borders, he was creating a force and a field that could recapture the lost lands of the Western Roman Empire (Johnson 2006).
    Diocletian would use mastery of bureaucratic and military growth, constant campaigning, and construction projects to increase the states expenditures, which, in turn, would lead to the necessity of more military growth to continue campaigning to continue to create more revenue. Building on third-century trends towards absolutism, Diocletian himself wasnt immune to egoistical urges, consistently elevating himself above the empires masses and imposing forms, regulations, and architecture (Baynes 1925). It would eventually be this autocratic nature that would be behind the standardization of imperial taxation in 297, levied to continue to push the empire towards expansion (Roman Colloseum 2008).
    With the essential policy-making behind the restoration in light, Diocletian also instituted a number of archeological developments for the frontier as well. First off, though, what exactly was the use of frontiers in the first place during Diocletian and Constantines time While both emperors held a firm grasp of the military function, perhaps their downfall was a lack of knowledge into the other functions of a frontier in regards to the empire. Pat Southern vividly explains this detail
The way in which the frontiers worked has been much debated. One of the connotations firmly embedded in the term frontier is that it will naturally have a military function, but a variety of other functions has been suggested for all the frontiers of the Empire as customs barriers, intelligence bases, aids to police work inside and outside the provinces, fortified communication routes, and not least, the delimitation of Roman territory. (Johnson 2008)    
Both Diocletian and Constantine I understood the military aspect behind managing the frontier. In addition to the aforementioned policy-changes to shore the frontier up, Diocletian also remodeled late Roman fort design, incorporating new defenses and layouts for the soldiers specific for frontier lands like the Danubian Frontier. For example, Diocletian was directly responsible for changing the styles of the forts by adding U-shaped towers at certain distances to enhance field vision, as well as allowing for a new system of attacking before being attacked (Johnson 2006). Contrast this design with the old design of reactionary actions in regards to Roman border disputes. In fact, Dicletian even attempted to rebuild and repopulate forts that were casualties of the Third Century Crisis, however, Constantine I would ultimately reverse this move, placing soldiers back in the cities and out of the forts (2006). 
    The prevailing character behind Constantines government, however, was one of conservatism. Contrary to what some might have expected, Constantines adoption of Christianity did not lead to any radical reordering or systematic revision of the Empire as a whole. This would go to include general military architecture as well. What Constantine focused on was completing most of the arrangements for the Empire already set up by Diocletian before him, primarily those involving provincial administration and army organization, the two most important aspects to the restoration of the empire (Pohlsander 2009). Constantine did not neglect the security of the frontiers either. He campaigned successfully in 306-308 and 314-15 on the German or Danubian Frontier, in 332 against the Goths, in 334 against the Sarmatians, and again in 336 on the familiar Danube Frontier (Barnes 1976).
    While Diocletian established a basis for power for the Late Roman Empire, Constantine could be said to be the one who fully utilizes that base against the barbarian hordes of the frontiers. Architecture in the area is clear that in 328, Constantine built a stone bridge across the Danube between Sucidava and Oescus. Not only that, a Roman mile marker, a marker that gave the distance of one Roman mile, was on the road north of that bridge, indicated Roman movement across the frontier during the time of Constantine. It would seem, then, that in or before 328 that Constantine effectively decided to re-occupy part of Transdanubian Dacia through the use of that stone bridge. Utilizing the stone bridge to cross the river Danube into the northern barbarian held territories would become the cornerstone in Constantines quiet offensive of conquest of the Danubian Frontier (Thompson 1956).
    Constantine would be considered one of the most important Roman emperors for more than just military conquest though. He also proclaimed the Edict of Milan, granting religious freedom to the empire, and was victorious against Emperor Maxentius at the Milvian Bridge, another event significant to the rise of Christianity in the empire. His main archeological impact, however, was the creation of a new central, Christian city for the Roman Empire at Byzantium, which would impact military and civil architecture for the duration of the empire. (Gill 2009)
    It was during the waning years of the Roman Empire that two extraordinary figures rose to attempt to rebuild her once great prominence in the world. While their efforts ultimately could not stop the Roman Empire from being lost to the sands of time, their collective work during their reigns would forever transform what it means to be an empire. Emperors Constantine I and Diocletian would go down in history as not only two savvy political figures, but also as those who would galvanize and revolutionize the Roman base into pushing back into the Danubian Frontier, a move they thought would lead to the restoration of the empire to its former glory.