The original concept of the Limes derives from the Latin words limus "cross" and limen "threshold", which were marked by the early Romans for the demarcation of their fields and fields by boundary stones, wooden posts or natural obstacles such as rivers.
By Gaius Julius Caesar later fortified guards and Marschlager on army routes in enemy territory was called Limes. If no natural obstacles such as rivers or mountains could form a border between the Roman Empire and the enemy country, Limite Legionnaires (plural limes) were set up and supervised by troops. The limits were adapted to the local circumstances. Loose forts and watchtowers formed the border in North Africa and the east. On the Rhine, Danube, Euphrates and Tigris, the rivers were used as a border and patrolled by legionnaires occupied ships. Such boundaries were also called river-limes or wet limes. Some sections such as the Rätische Limes in its last stage of expansion or the well-known Hadrianswall, however, consisted of a continuous stone wall with watchtowers. However, this concept was abandoned in late antiquity and replaced by the concept of various sized castles.
The development of the attachment system:
Initially, the "Limes" consisted only of aisles that were cut in forest areas. This should make it possible to detect approaching troops and enemies at an early stage and to react accordingly with their own soldiers.
Later, the border was fastened by a braided fence and wooden towers. Due to the elevated position in the watchtowers, the soldiers could make enemies even earlier and give signals to the castles behind, so that their own soldiers could be sent to the defense. The construction of the watchtowers within sight of the next tower also allowed communication and information exchange between the towers.
The next step was the replacement of the plaited fence by wooden palisades and the creation of a ditch between the towers and the palisade.
The last stage was the replacement of the wooden palisade by a 3-4 meter high and 1 meter thick stone wall. The watchtowers were now partly built of stone or Replaced and were now located directly on the wall.
A uniform construction for the Limes there was not in the entire time. Several factors played a role in the design, e.g. the natural conditions, the enemy strength and the available resources. Thus, a long limes such as Hadrian's Wall consisted partly of a stone wall, on the other hand, only of earthen walls.
Function of the Limes:
The main tasks of the Limes were on the one hand the demarcation of the Roman Empire to the non-conquered barbarian areas, on the other hand the regulation of the goods and passenger traffic with the associated customs duties.
So the towers served to monitor the border. When needed and necessary a signal could be given to the fort several miles behind when the enemy was spied on. This could then send foot soldiers or cavalry to face the enemy can.
A complete, militarily controlled demarcation to the areas outside of the Roman Empire was not possible on its own because of the immense length of the imperial border. Moreover, in the course of time too many wars meant that there was a growing lack of soldiers to permanently occupy the Limes.
A not to be despised side effect of the Limes existed in the economic power, which brought this attachment with itself. Thus, in the vicinity of the Limes with the adjoining castles, the infrastructure was adapted by the legionnaires and the cultivation technique of food production and the hygienic standards of those of Rome. This benefited the population on the Roman side of the Limes, and the economy profited greatly from the purchasing power of the Legionnaires. On the other side of the Limes, the population, except for a few trades, could hardly absorb anything of the Roman way of life. It inevitably created a separation between a poor and sophisticated and a primitive society.
The fall of the Limes:
The social and economic differences between the Roman side of the Limes and the areas on the other side gave rise to a certain amount of envy over time. Thus, at the beginning of the third century, the Germanic tribes increasingly attacked the Roman side of the Limes, many of the Germanic leaders even being trained by the Roman legion, but then joining the Germanic tribes. So they knew the tactics and weaknesses of the Limes and the Legion. 233 large parts of the Roman legions were withdrawn from the Danube area and called in the war against the Persians, which led to a further significant weakening of the border fortification. The Germans used this circumstance and carried out extensive plunder campaigns. Although they were repeatedly beaten back by the Romans, the damage and the associated reconstruction of border fortifications, castles and villages stagnated.
By the middle of the 3rd century, the western Roman Empire was already in decline. One ruler followed the other, their own legions were wiped out in the Civil War, hired mercenaries paid themselves by looting and the Germans already invaded Gaul, Spain and Italy. The Limes thus neglected and became a no man's land, as the military resources were no longer available to secure.
In 274 Emperor Aurelian finally and completely cleared the Limes area and read the border back to the Rhine.
Under Diocletian's reign later fundamental reforms were introduced, with which he managed to stabilize the Roman Empire reasonably. From 290 onwards, they began to build new fortifications on the Rhine and Danube, and the number of troops could be increased again for a while.
In the middle of the 4th century Rome negotiated with the Teuton tribes by defeat, diplomacy or payments to negotiate various treaties that allocated settlement areas to the tribes and which also provided sections of the Limes for defense. Thus, by the end of the century, a certain peace and order could be restored throughout the Reich territory. However, this changed until the civil war in 394 between Eugenius and Theodosius I in which the Western Roman armies were wiped out against each other and the frontier defense was hardly possible.
In the 5th century, the frontier defense disintegrated. Due to the financial condition, neither buildings nor troops could be received and paid. For a long time the Limes had no obstacle for the Germanic tribes and they were able to roam almost unhindered.
You can find the right literature here:
The Frontiers of Imperial Rome
At its height, the Roman Empire was the greatest empire yet seen, its borders stretching from the rain-swept highlands of Scotland in the north to the sun-scorched Nubian desert in the south. But how were the vast and varied stretches of frontier defined and defended?
Many of Rome's frontier defenses have been the subject of detailed and ongoing study and scholarship. Three frontier zones are now UNESCO World Heritage sites (the Antonine Wall having recently been granted this status - the author led the bid), and there is growing interest in their study. This wide-ranging survey will describe the varying frontier systems, describing the extant remains, methods and materials of construction and highlighting the differences between various frontiers. Professor Breeze considers how the frontiers worked, discussing this in relation to the organization and structure of the Roman army, and also their impact on civilian life along the empire's borders. He then reconsiders the question of whether the frontiers were the product of an overarching Empire-wide grand strategy, questioning Luttwak's seminal hypothesis.
This is a detailed and wide-ranging study of the frontier systems of the Roman Empire by a leading expert. Intended for the general reader, it is sure also to be of great value for academics and students in this field. The appendixes will include a brief guide to visiting the sites today.
Life in the Limes: Studies of the people and objects of the Roman frontiers
Lindsay Allason-Jones has been at the forefront of small finds and Roman frontier research for 40 years in a career focussed on, but not exclusive to, the north of Britain, encompassing an enormous range of object types and subject areas. Divided into thematic sections the contributions presented here to celebrate her many achievements all represent at least one aspect of Lindsay’s research interests. These encompass social and industrial aspects of northern frontier forts; new insights into inscribed and sculptural stones specific to military communities; religious, cultural and economic connotations of Roman armour finds; the economic and ideological penetration of romanitas in the frontiers as reflected by individual objects and classes of finds; evidence of trans-frontier interactions and invisible people; the role of John Clayton in the exploration and preservation of Hadrian’s Wall and its material culture; the detailed consideration of individual objects of significant interest; and a discussion of the widespread occurrence of mice in Roman art.
Edge of Empire: Rome's Frontier on the Lower Rhine
"In this place, a poverty-stricken tribe lives on high terps and hand-built platforms, which raise their homes above the known high water mark. When the waves wash over the surrounding land, the inhabitants look like seafarers, but when the water subsides they have the appearance of shipwrecked people."
That’s how a Roman officer described the people living on the shores of the North Sea. To him and his comrades, this was the edge of the world. In the sea, he expected to find fabulous monsters, and on land, savage barbarians.
Every ancient author writing about the Low Countries, was preoccupied with the complete contrast between the civilized people of the Roman Empire and the tribes of noble savages or barbarians living outside it. Julius Caesar exploited this preconception to enhance his own reputation, boasting that he had overcome the "bravest of all Gauls"; Tacitus employed the same stereotypes when he described the Batavian Revolt; and, in Late Antiquity, the Franks were still described as resembling monsters.
The reality was different. The presence of the Roman army along the River Rhine radically changed the way of life in the small Roman province of Germania Inferior, and the need to maintain and feed this large army became a significant incentive for economic change. The tribes living along the lower reaches of the Rhine and close to the North Sea gradually began to resemble their occupiers.
Historian Jona Lendering and archaeologist Arjen Bosman have combined their considerable expertise to create a successful synthesis of historical and archaeological evidence, in this history of Rome’s Lower Rhine frontier. Their award-winning book is now available in English for the first time.
Protecting the Roman Empire: Fortlets, Frontiers, and the Quest for Post-Conquest Security
The Roman army enjoys an enviable reputation as an instrument of waging war, but as the modern world reminds us, an enduring victory requires far more than simply winning battles. When it came to suppressing counterinsurgencies, or deterring the depredations of bandits, the army frequently deployed small groups of infantry and cavalry based in fortlets. This remarkable installation type has never previously been studied in detail, and shows a new side to the Roman army. Rather than displaying the aggressive uniformity for which the Roman military is famous, individual fortlets were usually bespoke installations tailored to local needs. Examining fortlet use in north-west Europe helps explain the differing designs of the Empire's most famous artificial frontier systems: Hadrian's Wall, the Antonine Wall, and the Upper German and Raetian limites. The archaeological evidence is fully integrated with documentary sources, which disclose the gritty reality of life in a Roman fortlet.
Roman Military Architecture on the Frontiers: Armies and Their Architecture in Late Antiquity
The Roman army was one of the most astounding organizations in the ancient world, and much of the success of the Roman empire can be attributed to its soldiers. Archaeological remains and ancient texts provide detailed testimonies that have allowed scholars to understand and reconstruct the army’s organization and activities. This interest has traditionally worked in tandem with the study of Roman frontiers. Historically, the early imperial period, and in particular the emergence of the frontiers, has been the focus of research. During those investigations, however, the remains of the later Roman army were also frequently encountered, if not always understood. Recent decades have brought a burgeoning interest in not only the later Roman army, but also late antiquity more widely.
It is the aim of this volume to demonstrate that while scholars grappling with the late Roman army may want for a rich corpus of inscriptions and easily identifiable military installations, research is revealing a dynamic, less-predictable force that was adapting to a changing world, in terms of both external threats and its own internal structures. The dynamism and ingenuity of the late Roman army provides a breath of fresh air after the suffocating uniformity of its forbears. The late Roman army was a vital and influential element in the late antique empire. Having evolved through the 3rd century and been formally reorganized under Diocletian and Constantine, the limitanei guarded the frontiers, while the comitatenses provided mobile armies that were fielded against external enemies and internal threats. The transformation of the early imperial army to the late antique army is documented in the rich array of texts from the period, supplemented by a perhaps surprisingly rich archaeological record.