Having two Emperors, one in each half of the Empire did not halt the Roman Empire,s enthusiasm for Civil War.
In order to make up the drain on manpower each Roman leader was forced by lack of financial resources to recruit tribesmen into the army.
During the Republic and the early years of the Empire, the state always recruited auxiliary troops from the races they either conquered,or cowed into cooperating with them. These non-Roman troops were kept apart from the Regular Army.
Now however times had changed and these former auxiliaries were now fully integrated into the system. Wether they liked it or not Roman Officers had no choice!.
The former tribal leaders of these Foederatii or federated troops were made Prefects and their Warbands became Cohorts. They were then posted to areas within the Empire away from their original homeland.
For example, in 370AD a Saxon chieftain by the name of Fruomarius was made a Tribune and he, along with a "Numerus "( Cohort) of his men were posted to Britain.
Britannia had been suffering tribal raids for some time. As Imperial contenders tussled for Power, the Army had to operate despite troop shortages. The situation had not improved during 365/ 371 AD, in the Great Barbarian Conspiracy.
It seems the Roman Secret Service ( the Arcana) failed in collecting information on the preparations made by the various opposing Nations. The Western Frontier suddenly came under attack from the East, the North and South all at once.
The Germanic Allemani, Franks and Saxons, were plundering Gaul and Raetia.
The Sarmatians and Quadii were attacking Pannonia.
Picts, Frankish pirates, Frisians, Scotti and Attacotti ( also known as the Del Riatta? ) were raiding South of Hadrians Wall. These tribesmen were coming over or through the Wall where it was thinly held. When not attacking the Wall they would sail down the East or West Coast and outflank the Wall completely.
The Asturianii of Tripolis and Berbers were raiding colonies on the North African coast. At one stage the Romans could not retaliate because of the lack of pack camels.
The Goths were raiding Pannonia, and the Persians Armenia.
Roman troops in Britannia had not been paid, therefore they deserted and formed bands of looters sometimes even joining with the tribesmen.
In 368AD Theodosius came to Britannia to correct the situation.Marching from London he sent out companies of soldiers lightly armed to break up the mobs of mutineers and bandits along with marauding tribesmen.
After about a year of campaigning Theodosius managed to restore order. Mutineers were executed and tribal raiders were killed or driven off. Hadrians Wall was regarrisoned.
The 6th Legion upgraded their fort at Eboricum. ( modern day York ).
In 383AD the acting Commander of the British Army, Magnus Maximus was proclaimed Emperor by the troops. Maximus took a fair number of troops from the North of England and headed to Gaul for a showdown with the current Western Emperor Gratian.
In the subsequent battles Maximus was killed. Many of his soldiers did not want to return to Britain and so they settled on the West coast of Gaul. The area was called Brettania which was also known as Amorica (modern day Brittany ).
In 398AD the Western Roman Magister Militum ( Army Commander in Chief ) Stilicho, came with an army to Britain. He waged a campaign against the Picts and the Scotti setting out from the fortification of Hadrians Wall.
His force was said to be nine Units of Commitatenses ( these were regular field army troops maybe 18,000 men ). By about 350 AD, the old Legions had been split in half ,each part being known as a " Junior" or " Senior" formation.
In the Eastern part of the Empire some of the old Legions may have still retained their original formation. The new formations were about 2000 men strong, and were all one type of Infantry. Cavalry formations were also of 2000 men and again were all the same troop type.
This was ok for the bigger battles, but increasingly warfare was being fought by smaller formations within the Empire itself: A) because of the lack of resources, and B) Roman troops could not be everywhere to counter the tribal incursions. It was not unusual for regular troops to face " barbarian" troops dressed and armed in the same fashion!.
Most military formations were either Infantry Cohorts ( Numerus) or Cavalry Ala ( Banda ), led by a Tribune or a Prefect. These formations were about 300 to 500 men in total.It seems that as time went on , if you had 300 men in your formation you were doing well,.
Larger battle groups were made up of a number of cohorts or Ala or a mix of both. Usually it was a case of making do with what was available.
On the rivers , Naval units known as " Riparenses" patrolled the major waterways in an effort to break up raiding Warbands, either before they crossed the border or as they made their way back encumbered with loot and slaves. The Roman vessels were painted blue/grey and held about 50 men.
The Rhine and the Danube marked the border of the Western Empire. In 367 AD and for two years after, the Rhine flooded making it difficult to campaign in the area.
Events on the Continent continued to slowly disintegrate as Germanic tribes pushed Westward. Senior Germanic Chieftains obtained Praetorian status in the Army as Roman Emperors and Generals were forced to negotiate. Lack of troop numbers meant that sometimes matters could not be settled by main force.
These Tribal recruits were given training but stilled retained some of their own customs. The Roman Army was becoming less " Italian" and more " Germanic". Even the Eagle Standards were being replaced with the Draco, a metal dragons head on a staff with material attached shaped like a Windsock. Such was the situation as Britain headed into the 5th century and more problems on the horizon.
Addendum added 8th July 2020:
Having read more about the 3rd and 4th century I am more inclined to believe that the " Saxon" raiders mentioned in the histories are Frankish or Frisian pirates. The reason for this is that there were already Saxon Federated troops within the Roman army, some being posted to Britannia. The Franks and Saxons detested each other and, at this time the Saxons had not yet migrated to the West coast of Europe. The word "Saxon" may have been used by the Romans to describe all Germans.
The figures in the illustrations are Hat Industries with some Newline Designs. The ship's crew are Emhar Viking crew. The spears and javelins are from North Star. Some of the shields are from Magister Militum.
The boats are scratch built, along with the fort and the ballista. I think the buildings are Hovels and Peter Pig. The tree area bases and road sections are S and A Scenics. The trees are various manufacturers.
The wagons, mules and civilians, are from Ceaser Miniatures Roman Supply Train boxes.
