(In which Tim discusses the five most important battles within the wider history of the 4th Century Roman Empire)

The fourth century was bookended by two famous ‘Christian’ battles - The Milvian Bridge in 312 and The Frigidus in 394. They mark - apocryphally - both the entry point of Christianity into the Roman Empire and its ultimate victory. Each led to climatic events; The Milvian Bridge led directly to the Nicene Council of 325 which formalised the Christian creed. The Frigidus began the series of events that ended with Alaric’s sack of Rome just sixteen years later.

So we have our beginning and end. What in between? Adrianople, of course. The defeat of Valens and the Eastern Roman Empire’s army at the hands of the Goths in 378 is popularly associated with the eventual downfall of the empire itself. Can’t argue that it’s important.

For me, Julian is the most interesting fourth century Emperor. His metamorphosis from bookish princeling to ass-kickin’ Caesar began in Gaul. The most famous battle in his journey to pacify the province was his victory over the Alamanni in the Battle of Strasbourg 357.

Our fifth battle is The Battle of Mursa 351 where the forces of Constantius II defeated those of the usurper Magnentius in the biggest and bloodiest battle of the century. As an exercise in damaging futility this was the daddy of them all.

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The Empire at the beginning of the fourth century was a very different animal to that ruled over by Septimius Severus one hundred years earlier. The crisis of the third century had brought about chaos, short lived emperors, and the temporary division into three mini empires. The gradual restoration of control was brought about by the Illyrian emperors Claudius Gothicus, Aurelian, Probus and finally Diocletian.

Diocletian instituted the tetrarchy - a system where two senior Augustii and two junior Caesars ruled quadrants of the Empire. It was a neat idea. It didn’t last. Diocletian, who resigned along with his co-Augustus Maximian, lived long enough to see not only his fine cabbages grow in his retirement home in Split, but his system of government fall apart as his successors squabbled amongst themselves to gain and maintain power.

Constantine (The Great), son of one of Diocletian’s successors Constantius I, was chief amongst those squabbling. He was annoyed that he was left out of Diocletian’s succession plans and, on the death of his ailing father in York in 306, declared himself emperor. This led ultimately to the first battle of our series - The Milvian Bridge.

In this battle, Constantine marched into Italy in 312 - then under the rule of one of the many post-Diocletian claimants - Maxentius. With a smaller army, Constantine’s troops feared losing the climatic battle outside Rome the next day. That night Constantine dreamed of a cross in the sky. So the story goes, he had his army paint the Christian symbol on their shields and, with God on their side, they routed Maxentius and his army the next day at The Milvian Bridge.

The Arch of Constantine was completed to mark this famous victory. The fact that it was originally going to be the Arch of Maxentius and repurposed bas reliefs from earlier monuments, is now somewhat forgotten. He who wins writes the history and gets the arches. It still stands today under the shadow of the Colosseum.

The next twelve years were a history of Rome fighting itself as Constantine gradually consolidated his power to become sole emperor in 324 with his defeat of Licinius. Famously, Constantine left three legacies to the Empire when he died - after converting on his deathbed to Christianity - in 337:

• The Council of Nicene which produced a unified - though disputed for many years - Christian doctrine still in use today,

• The founding of Constantinople as the ‘new Rome’ on the site of the Greek city of Byzantium,

• An utterly chaotic carve up of the Empire between his three sons and two nephews which set the scene for nearly twenty years of civil wars.

The intrigues between the three sons of Constantine deserve a blog of all their own. The imaginatively named Constantine, Constans and Constantius battled it out for years until only the latter remained standing as Constantius II. The second of our landmark battles occurs in this period when Constantius - in the East - took on his brother Constans’ murderer, Magnentius at Mursa in 351.

Mursa was a triumph for Constantius but a tragedy for the empire. Crack units of the East and Western Roman armies fought each other in a bloodbath in Pannonia (modern day Croatia). The battle saw the flowering of the late Roman cataphracts - heavily armoured cavalry - as they mowed down Magnentius’ legions. It was a victory but a pyrrhic one.

One of the consequences of Rome turning in on itself was that units were inevitably withdrawn from the Empire’s borders. The tribes living beyond took advantage of this and increasingly began to run amok amongst the frontiers. Constantius proved Diocletian’s theory that the Empire was too big for just one ruler and so appointed first his cousin Gallus, and then his other cousin, Julian, as junior Caesar. Gallus proved himself unfit to rule and so was executed. Julian however, proved himself quite the opposite.

Bookish, sceptical and a lover of philosophy, Julian was an unlikely warrior Caesar. Sent to Gaul to restore order, Julian did just that. And more. Let down by his supporting army (who may have been acting on the orders of Constantius) Julian was left facing a much larger force of Alamanni near Strasbourg in 357. The battle was a complete rout with the Alamanni destroyed by Julian’s infantry and then chased all the way back to the Rhine where many survivors drowned. Over the following years, Julian followed up by a process of forward-defence - raids into enemy territory whilst repairing and reinforcing the border.

Inevitably the two last descendants of Constantine The Great squared off against each other in 361 (see previous blogpost). Luckily for the Empire, Constantius died on the way to confront Julian allowing the latter to become the undisputed ruler of the whole empire. Julian met his ‘spear of destiny’ just two years later fighting the Persians and bringing to an end Constantine’s line and any anti-Christian fight back. Rome was henceforth a Christian empire.

The Empire now fell into the hands of Valentinian who appointed his brother Valens Augustus of the East. This proved a fatal decision as Valens allowed a massive Gothic migration into his lands in 376. The Goths crossed the Danube to escape the growing power of the Huns expanding and terrorising from the east. Stupidity, betrayal and pride (Valens refused to wait for the army of his nephew Gratian - now Emperor of the West) led Valens and the Eastern Roman army to take on the Goths alone at Adrianople (now part of European Turkey) in 378.

Adrianople was a disaster for the Romans. Their army was destroyed by the Goths and the emperor himself allegedly died after been burnt alive in a peasant house while attempting to flee the battlefield. The defeat left the Eastern empire defenceless and leaderless and at the mercy of the Goths who now rampaged at will throughout Thrace and Greece.

Slowly, piece by piece, Roman general and later emperor Theodosius (The Great) put the East back together. He fought defensive actions and eventually made peace with the Goths in 382 allowing them to stay within the empire’s borders. Once inside the Goths became a combustable element, fighting for the Empire when it suited them but, equally likely to go marauding and looting.

Over in the Western half, Valentinian’s younger son Valentinian II - now Emperor - allegedly hanged himself. His all-powerful advisor and military commander Arbogast was more than implicated. Arbogast was a Frank by birth and so ineligible to take the throne himself and so he chose Eugenius, an obscure Roman official to be the new Emperor in the West. Over in the East, Theodosius bided his time. But when Arbogast and Eugenius started to favour the old Roman gods over Christianity, Theodosius reacted. The showdown took place at The Battle of The Frigidus (modern day Slovenia) in 394.

This two day battle was notable for several things.

• Theodosius won the battle becoming the last sole Emperor of East and West. Not for long though as he died in 395.

• The battle marked the final victory of Christianity over paganism. Much is made of the high winds that allegedly blew at Arbogast’s forces on day two of the battle rendering their missiles useless. A divine wind, it was claimed.

• Theodosius’ use of Gothic auxiliaries (foederati) was controversial. He put them in the front line and used them as cheap cannon fodder. It allowed him to win the battle but incensed his surviving allies. One of the Gothic leaders fighting for Theodosius that day was a young noble named Alaric. Sixteen years later, Alaric led the Goths into Italy and sacked Rome for the first time in eight hundred years. It wasn’t the end of the Roman Empire but it marked the beginning of the last stages of the Western half.

The fourth century ends with the young sons of Theodosius - Honorius and Arcadius - in charge of the West and East respectively. Both of them were weak, dominated by advisors and unfit for their times. It was a sad end to such a lively century.

So what have learnt in this brief canter through the years 300-399?

First, and most obvious, the rise and rise of Christianity. A persecuted sect at the start of the century - the worst repression occurred under Diocletian for example - it was the undisputed religion of the Empire by the end.

The Roman military was still powerful throughout much of the century. Although the legions were no longer the primary unit, it still packed a punch. Borrowing from Palmyra and Persia, the military incorporated heavy calvary units alongside smaller vexallations of infantry. When it worked, armies could criss-cross the empire and successfully see off threats. Under strong leaders - Constantine, Julian - the army could be formidable.

The increased use of foederati - allied non Roman troops. By the end of the century, the traditional auxiliary units - trained and led by Romans - had largely been replaced by unincorporated bands of barbarians who fought under their own banners and leaders.

Civil wars were as deadly to the empire as attacks by outside forces. Roman v Roman battles were as common and - pace Mursa - could be much more deadly.

The idea of a single emperor ruling the whole empire was the exception rather than the rule throughout the fourth century. It was a rare period that saw just one ruler.

Read other Rome: In Five Battles here.

(I attach David Bowie’s Velvet Goldmine. When I was younger, reading about the later Roman Empire, I always associated this song with the heavily armed Cataphracts riding East to West, West to East, protecting the Empire. I misheard a line so it read “I’ll be your faithful prince who will ride for you again and again.” Unfortunately I now know that’s not the lyrics!)