The Battle of the Frigidus: When Rome's Gods Went to War
- Adam Lofthouse
- Jul 6
- 5 min read
Updated: 5 days ago
If you've been following the Shadow of Rome series, you'll know that Barbarian and the Throne is out on August 24th. The book builds towards one of the bloodiest days in the empire's long and bloody history: the Battle of the Frigidus. I promised a separate post about it, so here it is.
It's a battle that is fascinating, because it was so much more than two armies meeting in a narrow valley. On the surface it was a civil war, Roman against Roman. But by the time the dust settled, it had been remembered as something far grander: the last stand of the old gods against the rising tide of Christianity. Whether that's true or a story told after the fact is one of the most interesting questions in late Roman history — and we'll get to that. First, let me set the scene.
A civil war dressed as a holy war
The year is AD 394. In the West sits Eugenius, a respected teacher of rhetoric who had been raised to the purple by the Frankish general Arbogastes after the mysterious death of the young emperor Valentinian II (covered in Barbarian and the Throne). In the east sits Theodosius, a devout, uncompromising Christian who had already spent his reign stamping his faith onto the machinery of the state.
Eugenius himself wasn't said to be a pagan. But his regime became a magnet for Rome's old religious aristocracy. Under his rule the pagan temples were reopened, the ancient altars saw sacrifice again, and the senate of Rome — proud defenders of the old ways — flocked to his cause. To Theodosius, marching west with his legions and more than twenty thousand Gothic warriors under a young chieftain named Alaric, this was no longer just a fight for control of the empire. It was a fight for its soul.
Jupiter and Hercules take the field
Here's what gives the Frigidus its legend. Before the fighting began, Eugenius and Arbogastes are said to have planted a statue of Jupiter on the heights overlooking the battlefield, and marched their men beneath banners bearing the image of Hercules. The message was unmistakable. This was the old Rome — the Rome of the gods who had raised her from a village on the Tiber to master of the world — making its stand.
And on the first day, the old gods looked to be winning.
Theodosius attacked almost at once, throwing his Gothic allies forward into the teeth of the Western line. It was a slaughter. Thousands of them are said to have fallen. As night fell, Eugenius handed out rewards to his men and Arbogastes sent troops to seal the mountain passes behind Theodosius, trapping him in the valley. The Christian emperor's grand crusade was, by any honest reckoning, on the very edge of disaster.
The wind that "chose" Christianity
Theodosius, knowing himself to be beaten, spent the night in prayer.
At dawn on the second day the battle turned — and it turned on the weather. A ferocious wind came screaming down the valley from the east. The bora, a brutal, cold gale that still tears through the region today. It hurled dust and grit into the faces of the Western soldiers. Primary sources write that it caught their own arrows and javelins in mid-flight and flung them back at the men who'd loosed them (debatable, but good material for this writer!)
Arbogastes's line broke. Eugenius was captured and beheaded. Arbogastes fled into the mountains and, after a few desperate days, fell on his own sword. To the Christian writers who told the story afterwards, there could be no clearer proof: God himself had ridden the wind into battle. The church historian Rufinus set the Frigidus alongside Constantine's victory at the Milvian Bridge — the two great moments when heaven had reached down and handed the empire to the faithful.
What the Frigidus meant for the gods of Rome
Whatever really happened on that field, the consequences were real enough. The Frigidus is remembered as the last time a Roman army marched openly under the banners of the old gods. There would be no second attempt. The temples that Eugenius had reopened were closed again for good, the altars silenced, and the machinery of the Christian state rolled on without a serious rival.
The old religion didn't vanish overnight — it lingered in the countryside, in private homes, in half-remembered festivals for generations. But as a public, political force, as the religion of the Roman state, it died in that valley. After the Frigidus, the future of Rome belonged to the Church.
The last man to rule a united Rome
There's one more reason the Frigidus matters, and it's the thread that runs through everything I'm writing in these next books.
When Theodosius won that battle, he became sole master of the entire Roman world — East and West, from Britain to the deserts of Syria, under one man's command. He was the last emperor who could say that. He would not, however, rule it for long.
Just four months later, in January 395, Theodosius was dead. He left the empire to his two young sons — Arcadius in the East, Honorius in the West — and it would never again be ruled by a single pair of hands. The line drawn between those boys became permanent. The East would endure for another thousand years as Byzantium. The West would stagger on for barely eighty, propped up by the very man standing at Theodosius's side at the Frigidus: the great general Stilicho, whose rise and fall is the story I'm telling now.
So the Frigidus is a hinge. On one side, a united empire and the old gods. On the other, a divided world and a Christian future. Everything after it is the story of the West coming apart — and of the handful of men who fought to hold it together.
This is where Videricus, my young Greuthungi warrior, fits into the story. Born a pagan, fighting for a Christian faith he does not believe in, for an empire he does not belong to. Just his blind loyalty to Stilicho keeping him in the battle line.
Whilst researching the battle of Frigidus, I came across this video on YouTube. Obviously take any historical accuracy with a pinch of salt, but it's entertaining and it did give me a feel for the battle when it came to writing it at the end of the book!
Barbarian and the Throne, book four of the Shadow of Rome series, is out on 24 August. If you enjoy Roman historical fiction in the vein of Simon Scarrow, Ben Kane, Conn Iggulden or Harry Sidebottom, you can pre-order it now — and follow Videricus, Stilicho and others into the crucible of civil war.
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