I'm excited to announce our channel’s
first official merch! So you can now have your favorite Empire and Legions on
your clothes, not just not your mind! We spent a lot of quality for the lowest prices,
so check them out from the description below! All future Patreons above this rank will be
getting a custom shirt with their name on it! For most of the Western Roman Empire, the largest
and most troublesome frontier was the one along the Rhine and Danube rivers. The legions stationed
along this over 2000 km long border were subject to continuous incursions by Germanic tribes,
who were responsible for some of the largest military defeats that would lead to the ultimate
demise of Rome. But despite these few failures, in large part due to continuous internal
civil wars, the Roman system of guarding and maintaining this border was so ingenious, that
it stood unshaken for centuries, always shifting, adapting, and crushing incoming armies,
while allowing its western provinces to thrive in safety and peace… The Rhine and Danube
rivers were highly effective natural defenses, but they had a small weakness. In the area know
as the Agri Decumates, both rivers are born and flow differently, creating a small chink in the
Roman defensive line, and a narrow gateway for any invading army to comfortably march through,
and be at the heart of Rome in a matter of days. In this video, we decided to focus on THIS
area, not only covering its evolution in becoming one of the most complex and
fascinating Roman frontier systems, but also explaining how the Romans thought
and approached the idea of frontier defense, and of course, recreating parts of it
in 3D… Without further ado, let's begin! The Agri Decumates would grow to become a
VERY formidable frontier, but surprisingly, it was not a project of a single Emperor or
military commander as one might assume. In fact, it took decades for the whole area to be conquered
through numerous short-term projects done by different emperors, all aimed at solving specific
smaller plans, rather than a single grand goal. The region first entered the Imperial agenda in
the aftermath of the Year of the Four Emperors and the Batavian Revolt. These events outlined
that although the Rhine frontier was strong, it had many weaknesses which called for a
new system to be put in place. The provinces of Germania Superior and Raetia were, until this
point, fairly isolated in guarding their sections of the frontier, and the first upgrade Emperor
Vespasian and his successors did was to construct a road which connected the legionary bases of
both provinces, together with the necessary forts and other installations to keep this route secure.
Each fort shown here had a garrison of two hundred men at best, and operated as the headquarters
for the several watchtowers and fortlets around each one. The entire project would only be
fully completed during the reign of Domitian in the mid 80s AD, and would ensure the rapid
mobilization and response time of troops between, not only the two provinces, but the entire Rhine
and Danube frontier systems… After the infamous war against the Chatti in the mid 80s AD, Roman
forces began securing large tracts of fertile land to the north. To shield them from Germanic
raids, a system of forts was built around them. During the reign of Trajan, the first attempt to
create a definitive frontier was made. With Rome’s forces tied up in the distant wars with Dacia
and Parthia and new lands being incorporated into the Empire, saving up precious manpower was the
challenge. Weak points were reinforced with new fortifications, and the gap between the Neckar
and Main rivers was finally closed off. After Trajan, Emperor Hadrian would add his own touch to
the defenses by building a three meter tall timber palisade that spanned hundreds of kilometers,
thus clearly marking the border and limit of the Roman Empire, at least only in Germania
Superior (in the late 110s and early 120s). It is only in 158, over 30 years later,
under Antoninus Pius, would Raetia also start constructing a palisade of its own.
In an attempt to secure the more fertile land east of the border, a new 80 kilometers
long defensive line was built from scratch following the same principles applied by
Trajan and Hadrian. Antoninus’ decision must have caught many local commanders completely
by surprise. At the fort of Elztal-Neckarburken, for example, the local garrison had just finished
constructing and renovating their bathhouse, a very expensive and complicated building to
construct, when they were ordered to demolish everything and move 30 kilometers to the
east, which historians have called the “outer limes”. Regardless, all constructions
were quickly finished by the year 165. Under the reign of Marcus Aurelius, a few more
forts were built, and the now decaying palisade was in some places replaced by a 6 meter wide
ditch and rampart or stone wall. Interestingly, in Germania Superior the towers remain
detached from the ditch or rampart, but in Raetia, the stone wall was
integrated into the towers. This change could be seen right at the border
between the two provinces, implying that their governors were likely each responsible for
the defensive constructions in their regions, while still keeping everything cohesive and
singular; once again, “organized chaos”… The way everything organically progressed
through the years once again onlines an underlying theme that repeats itself in
every video we make about the Romans, and that is that they relied on a system of
“organized chaos” in everything they did, and this section of the frontier was no different.
At first, parts of it may seem unnecessary, redundant, or not fortified enough, and as if
a straight consistent line of defenses would be a better option. But upon closer inspection,
one can slowly realize that is not the case, and everything was impressively optimized for its
purpose. The overextended forts in the north were skillfully tailored to maximize every advantage
of the terrain, and positioned along the highest peaks of hills, being thus able to detect
danger much further away than if they were positioned along a straight. And forts like
Saalburg protected vital passageways into the region. Their extreme position also protected a
sizable chunk of fertile land upon which several military colonies and civilian settlements were
created, to both act as a buffer zone and provide the frontier with supplies and manpower… The
lack of a palisade in some areas was only due to the presence of a river, which served as a
natural defense that disregarded the needs for a palisade, as it would only take up unnecessary
time and supplies to construct... The area in the east might seem underdeveloped and weak, but that
is only because the Romans paid careful attention to local population densities, and tribes ahead of
this area were less numerous and fairly unhostile, allowing less men to safely garrison this area…
Only when areas were flat or heavily forested did the Romans create a straight line of defenses
to use the least possible amount of materials and manpower. THIS section was actually so perfect
that it varied in straightness by only 1 meter from start until end; quite impressive
if you think about its length. Similarly, by not just closing the gap between the Rhine and
Danube, the Romans were able to cut the distance of the entire frontier. This policy allowed
the Romans to maximize their limited manpower reserves to maximum effectiveness, thus being able
to free up vital troops for unexpected campaigns… If you’re like me and enjoy browsing
the web with hundreds of tabs open until you’re either losing them or
closing them by accident, it may be time to switch to the Opera browser,
with whom we partnered for this video… As you can see, they have a lifesaving feature
called Tab Islands, that is a super easy way to group your articles into folders, for a more
organized browsing experience. They also have an integrated AI tool called Aria, which is really
helpful for quickly getting the answer to basic questions! Also located on the sidebar are icons
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then I'm sure like me, you won't wanna go back! This 550 kilometer long frontier encompassed
not only 60 forts, but also 90 fortlets, and about 900 watchtowers, which were too
small to be shown on this map. And all of them were at some point expanded, downgraded,
relocated, or simply abandoned to suit the needs of emperors and local commanders
alike. Maintenance was another reason that buildings had to constantly be worked
on. Wood was the primary material used, but because it had a lifespan of only a few
decades, soldiers would have been forced to constantly replace decaying materials for
new ones or move to new positions altogether… Shown here is a reconstruction of one of the
many watchtowers (Hesselbach-10/33) built by Trajan and Hadrian (along the Odenwald Ridge),
and our model belongs to the later stages of occupation in the mid 140s, when due to the
decaying of the wood, the tower was rebuilt in stone and plastered in white, with a roof of
oak shingles. It is a rather small construction, and such watchtowers were built at every 500-600
meters along the palisade. The tower’s entrance was on the second floor and was only accessible by
a ladder which could be pulled up and stored away in case of an attack. A watchtower like this would
only accommodate 4 to 8 men, who all served on the second floor, while the ground floor acted as a
storage facility. The protruding gallery granted the soldiers a 360º view of the surrounding
landscape, enough to spot any sizable force well in advance and transmit a signal to neighboring
outposts. As such, these structures had to be clearly visible by other nearby positions in order
to communicate effectively. We can assume that watchtower garrisons were not meant to engage the
enemy or intercept any incoming raids, but instead to passively survey the countryside and report
any suspicious activity. But this didn’t mean they were completely harmless. Remains of multiple
missile weapons have been found in many of these structures and suggest that at the very least
they could offer a token resistance when needed. Located about a kilometer behind the watchtowers
would be fortlets, positioned between the key forts. This here is the fortlet of Rötelsee
(Römisches Kleinkastell Rötelsee), built during the construction program of Antoninus
Pius, near the modern town of Welzheim in Germany. Situated on a small hill (east of the
Limes Road), this fortlet was abnormally close to the Limes palisade, being only 40 meters
away from it. Fortlets like these were built to defend strategic places and bridge the
gaps between the larger forts and make it harder for raiding parties to slip between them.
These structures were also fairly small in size, with this one measuring 18.5 meters on each
side, and housing only a couple dozen men. The fortlet itself had very limited defensive
capabilities, with only a ditch, 2.5 meter high walls, and no towers for protection. This fortlet
was accessed from the western side, the one facing the border; where the ditch was interrupted
by three improvised earth bridges which could be barricaded in case of an attack to create
an additional defensive line. Over the ditch, a small single gate granted access to the
fort. Inside the fort was built a single U shaped wooden structure that acted as the
garrison’s barracks, storage facilities and command center. The inner courtyard also hosted
a large fireplace where the garrison would cook and eat their daily meals. On the south side, a
small sewage canal was also present, that would allow the disposal of any waste into the ditch
outside. Even the smallest of Roman positions had to stay neat and clean… Given the reduced size
of the garrison, buildings like the praetorium or principia are absent here, as all the members
of the garrison would have been below the rank of centurion and therefore not allowed the extra
space enjoyed by their superior officers. In fact, many of these positions were assigned temporary
commanders from the immunes or principales, the higher ranks of Roman legionaries. These,
tasked as curatores would run the daily routines and tasks in these fortlets, thus distributing
orders from the main Legionary forts further back, and creating a network from the largest forts
to the smallest of watchtowers. After all, the primary duty of these fortlets was the manning
of local watchtowers, to which they rotated men on the daily. They were also charged with traffic
control of authorized crossings through the frontier gates, the monitoring of activity
beyond the frontier palisade and finally, the interception and destruction of small raiding
parties that managed to slip through. As you can probably tell by now, Romans never thought of
border defense as an impenetrable barrier. Even the palisades were never really intended
to prevent attacks, but rather to funnel in public traffic through specific outposts in
order to better control movement. After all, a lot of trade and cultural influence occurred
between the Germanic and Roman people, and through the centuries, many along the border grew fairly
reliant on each other. The same thought process was applied to some degree in Rome’s other
borders too. In North Africa, some parts of the border were particularly weak and overcrowded
by trade, while Hadrian’s wall in Britannia was perhaps the closest to a solid border, though even
it worked more like a funnel than an impenetrable fortification, as any mid-sized attack could
fairly easily breach it. Roman borders were actually far more effective at slowing down
attackers on their way BACK after raiding, because even a thin wooden palisade or shallow trench is
a tough obstacle when over encumbered with loot. But the vast majority of enemy incursions
were fairly small, aimed at minor sabotage, reconnaissance, or even stealing and smuggling
for personal gain. Against these troublemakers, the small watchtowers and fortlets, armed by only
a few dozen men and supplemented by occasional mounted patrols, were highly effective. And
they were expected to track and catch them if possible. A surviving letter from Roman patrols
in Africa gives us a great example of this: “Fifty (?)camels [having been stolen] by 18 barbarians
(...) I have pursued [with?] three horsemen and infantry (...) through impassable areas and
we fought them (...) But, surprised during the night (...), we retreated to the fortlet (...).”
Regarding larger incursions, their role was largely unknown. After raising the alarm and
signaling nearby positions, they would probably be expected to either fall back to regroup
or barricade themselves in the forts to delay the enemy, though we can’t be sure. Another
surviving letter speaks about this constant uncertainty and fear that the watchmen would feel:
“Bassus to Galates, his brother, many greetings. I beg you, brother, give me news of yourself often,
because you know that if there is trouble, I will not just be worried about you. Indeed, I fear
for myself, because we are not very many here.” Surprise attacks, skirmishes and raids could
turn a peaceful day at work into a fight for survival and the risk of an inglorious death
at the edge of the world. So most of the border was garrisoned by non-Roman auxiliaries, with
the large legionary fortresses being way in the back. But containing their fear was not the
only thing that watchmen would occupy themselves with. Many in the fortlets and watchtowers would
engage in activities to self sustain themselves, and sometimes even earn a side income. The
frontier had a well coordinated logistical system, but it was prone to interferences, delays,
or outright disruptions that would put strain on the soldiers along the border.
A surviving letter gives a great example of this: “. . .the ‘acisculus’ of the mill is
broken – the iron part – and there is nothing we can do . . . in the fortlet. I’ve dispatched
Krinolaios, cavalryman of the turma of Satrius, with the iron part in order for it to be
repaired. That is why we ask you, Lord, to return it at once. Indeed, we do not have
the means to live if the mill is not restored.” Despite the ever increasing germanic activity
and eventual breaches during the IIIrd century, the frontier in the Agri Decumates continued
to mark the edge of the Roman Empire through the IIIrd century until its final abandonment
in the late 250s and 260s AD. By this time, the numerous crises engulfing the Empire, including
the breakaway of a new Gallic Empire, meant that the frontier simply had to be given up. The land
would be instantly captured by the Alammani, who would launch incursions through it for the next
couple centuries. Today, thanks to the titanic efforts of German archaeologists, historians and
technicians, several places of the frontier have been reconstructed and are accessible to
the public as UNESCO World Heritage sites… We hope you enjoyed visiting the upper Rhine
Roman frontier! To see how it compares to other Roman frontiers, in the north and
east, check out our other videos here. And consider supporting our team on Patreon!
I hope to see you all in the next one!
