124 - The Tetrarchs at War

Hello, and welcome to the History of Rome, episode 124, The Tetrarchs at War. We left off last week with our two newly appointed junior emperors, Constantius and Galerius, ready to begin the wars they had been assigned by their senior colleagues. In the north, Constantius was making final preparations for his invasion of Britain, while in the east, Galerius outlined his strategy for punitive expedition against the Sassanids, who had recently broken their treaty with Rome by invading Armenia. For the moment, it looked like Constantius had drawn the short straw, forced to fight fellow Romans in an attempt to retake a nearly impregnable island that had thus far proved to be an impossible nut to crack. Galerius, on the other hand, got to fight Persians, and in addition to the riches and glory that usually came with campaigns in the east, Galerius also stood to be the man who finally avenged the long-unavenged capture of Valerian. Constantius' assignment was hard and unglamorous, Galerius' was, well, not easy, but certainly not as hard, and it was most likely going to prove ten times as glamorous.

But despite the relative difficulties of their respective wars, it would shortly be Constantius who was bathed in glory for reconquering the province of Britannia, and Galerius who was forced to walk a mile in front of Diocletian's litter as penance for the defeats he had suffered. To deal with the western front first, we must follow Constantius from Milan up to Trier, where he established capital for his coming campaigns. As I mentioned last week, Constantius was probably involved at the highest level in the previous attempt to retake Britain, and so was acutely aware of what had gone wrong. Two big mistakes appear to have stuck out to him. First, despite the understanding that they needed to pacify the Germans before proceeding, they had not taken this to its logical conclusion. That is, they knocked out all the periphery tribes and established a launching pad from the Rhine delta, but they had done nothing to directly attack Corotius' Frankish allies in northern Gaul. As long as Corotius controlled both sides of the English channel, not only would his supply and trade lines remain open, and those trade lines were a part of the key to his legitimacy, but he would also be able to concentrate his defense forces on the eastern approach to Britain, since that would be the only direction an invasion fleet would be able to come from.

So Constantius resolved to make his first objective, dislodging the Franks from the Gallic coast. Once they were out of the way, he would be able to deal with the second big mistake—namely, that a single invasion force approaching from a direction the enemy expected was no way to break through a naval blockade. You have to at least be a little sneaky about these things, and so Constantius resolved to be a little more sneaky when it came time to put his own ships in the water. Taken together, these two corrections wound up winning the war for Constantius. The first fatally undermined Corotius' regime. The second completely paralyzed his successor.

Right away, that is, in late 293 AD, just months after being made Caesar, Constantius launched the first of his attacks in pursuit of Objective 1—neutralize the Franks. The key port on the Gallic coast controlled by the Franks was Boulogne, and so, not beating around the bush, Constantius laid siege to the city in the autumn of 293. The Frankish leaders felt pretty good about their ability to hold out. Constantius was in no position to threaten their access to the sea, and the approach by land was thin and heavily fortified. But Constantius was not here to mess around, and, even though no one—probably not even his own men—expected it, the Caesar went right for the jugular and began to threaten the Franks' access to the sea. It is a little hard to describe, but in essence, Constantius had his men build a dam across the harbor, cutting off any possible sea traffic. Though he had no navy to speak of, Constantius was thus able to cut off the Frankish ships from their main port of call, and leave the defenders of Boulogne stranded without the possibility of relief. It did not take long for them to recognize that their situation was hopeless, and capitulate to Constantius' legions.

The capture of Boulogne, while in and of itself a good thing, actually turned out to be a bigger boon to Constantius' chances of winning back Britain than even he could have predicted at the outset. Because the loss of access to the mainland caused by the fall of Boulogne dealt a major blow to Corotius' legitimacy, and left him vulnerable to a murderous palace coup. I haven't been able to find a good answer to the question of what the conspirators thought they were going to accomplish by assassinating Corotius, but in the winter of 293, a cabal led by the British finance minister Electus killed the man who had been their Augustus these last seven years. With Corotius out of the way, Boulogne remained lost, and the little British empire was now deprived of its most able general. So yeah, I'm not sure what they were hoping to accomplish. Sometimes I guess power is its own reward. Electus declared himself Augustus, and the noose was pulled a bit tighter.

But the now practically inevitable execution of the British regime did not follow right away. The problem seems to have been that in the aftermath of Maximian's defeat, there was no concerted effort to rebuild the navy that had just been annihilated. So in the aftermath of his own victory at Boulogne some four years later, Constantius still had no navy. As with the reason for Corotius's assassination, I haven't been able to find a good explanation for why a fleet was not being rebuilt, especially since everyone knew there was going to be a second invasion attempt. But if I had to speculate, I would say that no one really knew when or under what circumstances the next invasion would take place, so why waste time and resources constructing a fleet that might sit idle for years, and in the interim be sitting ducks for Frankish attacks that might see the new ships destroyed before they even had a chance to launch. But I'm just guessing. All we really know is that following the capture of Boulogne and the assassination of Corotius, two years would pass before Constantius set sail to retake the island.

In the meantime, he seems to have followed the same basic policy as Maximian and Diocletian, and campaigned extensively against the Alamanni in order to ensure that the mainland would be pacified when he headed across the water. And of course, he continued to campaign against the Franks until they had been brought completely to heel, culminating with the placement of a new pro-Roman king at the head of their confederation. By 295, though, things were all set. Maximian moved up from Milan to watch the Rhine frontier, and Constantius readied his fleets to sail. What's that? Fleets, you say? That's right. Taking advantage of his control of the Gallic coast, Constantius divided up his forces in two, launching them from two different ports, with two different landing spots in mind, so as to divide the enemy and keep them guessing as to where the invasion was headed. Constantius himself launched from Boulogne on his way to Dover, while his Praetorian prefect Asclepius Dodus launched from the mouth of the Seine river on his way to the Isle of Wight.

Just as with Maximian's invasion, supposedly, the short trip to Britain was complicated by bad weather. But with two fleets on the water, instead of just one, the operation was able to keep moving forward, rather than coming to a complete standstill when Constantius's ships were stalled out in the storm. Asclepius Dodus' fleet was able to navigate the rough seas and make a landing somewhere near Southampton. Once ashore, the prefect burned his ships, not just to prevent their capture, but also to remind his men that there would be no retreat. Victory or death, that is what the gods had in store for them.

Now Electus, the self-proclaimed Augustus of Britain, who had been running the island for the last two years, was not a tenth of the soldier Corotius had been. Believing Constantius was coming from the southeast, since that is where the previous invasion had come from, Electus had massed his forces down in Kent to meet what he thought would be a single invading army. When reports suddenly began arriving detailing an invasion force marching north from Southampton, Electus panicked and pulled his forces up to block the road to London. But in his haste to get the army moving, they became disorganized and spread out, with the British legions proper divided from the Frankish mercenaries the British regime had been employing since Corotius first established his independence. So the defense force Electus planted on the road to meet the advancing Romans was not at full strength, nor well organized, nor well led. Asclepius Dotus did not have to work very hard to smash them to pieces, and Electus himself died in the fighting.

When the weather cleared up, Constantius landed his forces and began his own march on London. With the news of Electus' defeat already circulating throughout the island, the arrival of Constantius suddenly had a whole new vibe. The Frankish mercenaries who had not fought and died, were now viewed as a far greater threat than Constantius and his legions. The citizens of Britain were shutting up their homes and cities, not because they feared Constantius, but because they feared what the Franks would do now that they were off the leash. And their fear was well placed, as it appears that the Franks took Electus' defeat as their cue to sack as much of the countryside as they could. Constantius caught up with them before they reached London, though, and in a quick battle annihilated the marauding Franks.

When Constantius set sail, he had every reason to believe that the battle for London would be a hard-fought affair. But now, as he approached the capital, he found himself greeted not as an enemy, but as a beloved hero. This great and mighty Caesar had delivered Britain from the destructive wrath of the Franks. Just like that, the province of Britannia was reabsorbed, more than willingly at this point, into the Empire. To celebrate this victory, Constantius began issuing coins with his own face, bearing the legend Restorer of Eternal Light.

Just as Constantius was celebrating his victory in the West, Galerius was beginning his campaign. After spending most of the last two years in Egypt, the Caesar had been brought north to Antioch to confer with Diocletian and figure out what to do about the resurgent Sassanids. Diocletian had been watching with alarm as the new Persian king Narcissus adopted an increasingly hostile posture towards Rome. At first, this new posture manifested itself in relatively harmless displays of strength by the Persians along their western frontier. But lately, Narcissus had been making troubling alliances with the tribes and petty kingdoms of the borderland. Then, in either 295 or 296, the Persian king moved out of the theatrical and into the martial by invading Armenia, defeating and deposing the pro-Roman king Tiridates in the process. From Armenia, Narcissus moved his forces south through Osroeni, and stood poised now on the Syrian border.

Diocletian knew that Narcissus was self-consciously styling himself as the new Sharapur, and it was entirely likely that the Persian king was getting ready to invade Syria and sack Antioch, just as Sharapur had done. Diocletian was unwilling to wait for the other shoe to drop, and so, in mid-296, Galerius marched out at the head of an army to confront the Persians before they decided to cross into Roman territory. The two armies met near Cary, a site of Crassus's great defeat some three centuries before, and after wasting precious little time on diplomatic niceties, the Romans and Sassanids threw themselves at one another. The result was an unmitigated disaster for Rome. Galerius ran his heavy cavalry and archery detachments in perfect tandem, and this Persian one-two punch caught the Romans completely flat-footed. After suffering extensive losses, Galerius was able to extract what was left of his army and lead them on a limping march back to Antioch.

Legend has it that upon his arrival Galerius was met outside the city by a furious Diocletian, who made the defeated Caesar walk a mile on foot in front of Diocletian's imperial litter as punishment for his failure. It is likely that this episode is a colorful invention, but there is no doubt that in the aftermath of the defeat, Diocletian made Galerius take full responsibility for the episode. Such was the cost of maintaining the Tetrarchy's stability. Would be shared by all four men equally, but defeats would be the responsibility of the losing general alone. That being said, in all likelihood, Diocletian's public shaming of Galerius is a later invention. For one thing, no contemporary source mentions the incident, but perhaps more importantly, it would not at all have been in keeping with Diocletian's character.

The senior Augustus was careful to cultivate a public image of the imperial college as one of unwavering mutual support and unity of purpose, as was so demonstrated in the aftermath of Maximian's failed British invasion. To humiliate Galerius out in the open like that would not just have poked holes in that public image, but it likely would have done real damage to the actual unity Diocletian was trying to maintain behind the scenes. Eradicating the conditions that led to the rampant civil wars of the crisis years was one of Diocletian's biggest concerns, and I highly doubt that he would have so carelessly undermined all of his efforts by slapping his junior colleague around in public. Honor was a huge part of what made these men tick, and humiliating Galerius so brazenly might have ticked the Caesar off to the point that he would have viewed overthrowing Diocletian as a reasonable response. So while I have no trouble believing that Diocletian balled Galerius out in private, in public I can't imagine he would have done anything to risk imperial unity, especially for something as petty as making a guy walk in front of your horse for a little while.

But it was not all bad for the Romans. Despite the fact that he had been bested in the field, Galerius had obviously put up enough of a fight that the Persian king, whatever his intentions had been before, did not immediately follow up his victory with an invasion of Syria. And it's a good thing that he didn't, because just a few months after the defeat of Galerius, word came up from Egypt that yet another revolt had broken out. The origins of this latest unrest will be dealt with more fully a few episodes down the road when I dive into Diocletian's economic reforms. So just know for now that Diocletian's crackdown on tax evasion did not at all go over well with the perpetually tax evading Egyptians.

Leaving Galerius in Syria to oversee the rebuilding of the frontier defenses, Diocletian decided to personally see to the problem of Egypt. In 297, what had begun as a series of local uprisings had coalesced into a province-wide movement that even had its own self-proclaimed Augustus, a man named Lucius Domitius Domitianus, who was attempting to reassert all the special privileges Egypt, and in particular Alexandria, had always enjoyed and that Diocletian was now trying to take away. Diocletian, though, had a vision for the future of the empire, and special treatment for special people was not at all a part of that vision. Just ask the citizens of Italy, who, at that same time, were having all of their long-held privileges revoked one by one. Pay taxes? You've got to be joking. But like I say, we'll get into all that later.

So Diocletian came down to Egypt, and despite stiff resistance from the natives, he thoroughly smacked down the rebellion with an iron hand. The emperor had no intention of allowing Egypt to become the bleeding ulcer that Britain had been for so long, and mercy towards the rebels was in short supply. There is even a charming little story about how, when he finally took Alexandria after a surprisingly difficult nine-month siege, the enraged Diocletian announced that he was going to slaughter everyone in the city until the blood ran up to his horse's knee. Then, as if on cue, the tired horse decided at that very moment to kneel down, knees of course now touching the ground. Diocletian took the hint that God sent him in order to stop the massacre he was intending to unleash on the Alexandrians. This little story is even more charming because in gratitude the Alexandrians allegedly built a statue in honor of Diocletian's horse once the emperor had moved on.

By the end of 297, though, the revolt was nipped in the bud, Domitianus was dead, and the emperor could turn his attention back to the Persian problem. Back up in Antioch, Galerius had spent the year successfully rebuilding the Syrian legions, and when Diocletian arrived, the senior Augustus was pleased to discover that his junior colleague was ready to go back on the offensive. And it was the offensive they would have to go back on, because, despite his initially bold moves, King Narcissus had learned that the Romans were not the pushover he had perhaps led himself to believe they were. He didn't give up his position in Armenia or Mesopotamia, but he also didn't press on any further.

When it became obvious that the Persian king was not going to invade and press his luck inside Roman territory, the emperors decided to take the fight to him again. As we've seen over and over again, the Romans never took a defeat as the last word in anything, and it was in fact almost axiomatic that the last word had to be a Roman victory. If the Romans lost, it was only a setback on the road to final victory. It could not possibly mean an end to hostilities, because the only time the Romans allowed an end to hostilities was when the Romans won. They were simply a maddening opponent that way. So in 298 AD, Galerius marched out at the head of an army to track down Narcissus and bring an end to hostilities.

This time, the Caesar played it a bit smarter. Rather than heading straight for the Persian army, which was then encamped on the plains of Mesopotamia, he decided to take the road in through the mountains of Armenia, and force Narcissus to fight on ground that Galerius hoped would neutralize the Persian heavy cavalry advantage. Narcissus took the bait, and this time when the two armies met, the legions routed the Sassanids, though the battle was not at all decisive. Narcissus retreated and Galerius pursued, hoping to catch the Persians before they re-established themselves on better ground. Luckily, the Persian withdrawal was haphazard, and with the help of local guides, Galerius was able to close the distance between the two armies and launch an attack on the utterly surprised Sassanids when they were still in their camp one night. This time, the battle was decisive. Not only was the Sassanid army cut to pieces, but Narcissus was forced to flee for his life without being able to stop and collect his wives, his harem, or his royal treasury, all of which fell into the hands of the triumphant Galerius.

The Sassanid military was now broken, the king was now running for his life, and valuable hostages had now been seized. Now hostilities could end. Well, not quite yet. Galerius took a victory lap down through Mesopotamia in order to sack the Persian capital of Ctesiphon, which at this point was practically a rite of passage for Roman generals serving in the east. Unchecked, Galerius probably would have marched all the way to India, but he was stopped by Diocletian, who was able to see the bigger picture. Diocletian had no desire to rule over Persia. He just wanted peace with the Sassanids on the best possible terms, and with the king's wives and harem being treated with the utmost respect by their Roman captors, Diocletian was now in a position to leverage an even better deal than he had worked out with Bahram in 287, and leverage a better deal he did.

A summit was arranged between the Roman emperors and Persian ambassadors at Nisbis in 299, where Diocletian laid out his terms. After an amusing, but likely fictitious exchange that saw the Persian envoy's attempt to lecture the Romans on the importance of being magnanimous in defeat, and Galerius then practically blowing a blood vessel, demanding to know where the Persians got off lecturing the Romans about magnanimity when the stuffed corpse of Valerian was still being held as a Sassanid trophy. After this, the Persian envoys agreed to all the Roman terms. Not only was Armenia brought back into the Roman fold, but for the first time, the kingdoms of the Caucasus Mountains were made Roman clients, and cities on the east side of the Tigris were ceded to Roman control. In every way, Diocletian got the better of the Persians in the Peace of Nisbis, and the capture of the Persian royal family was understood to balance the scales for the capture of Valerian. All of which was nice, but what was even nicer was that the peace brokered in 299 would last for the next forty years, and that was a victory for everyone.

So it was that at the close of the third century, a century defined by the empire's near collapse, Rome was as strong as ever. Fifteen years of political stability overseen by one of the best leaders the empire had ever seen, internal revolts squelched, external threats neutralized, and a socio-economic order redesigned to match with the realities of this new age. Rome would never again be allowed the kind of freedom of movement it had enjoyed during its various golden ages, and it would indeed be a constant daily struggle just to maintain what Diocletian had established. But something had been established.

In the next few weeks, we are going to investigate what exactly had been established, starting next time with an analysis of Rome's new military posture. After that, we'll deal with Diocletian's economic reforms, including his famous Edict on Prices, and then cover his reorganization of the governmental apparatus. Taken together, Diocletian transformed just about every aspect of Roman life, but again, as I mentioned before, he was not trying to create a new world order. He was trying to save the old world order. And that's it. Thanks for watching. If you enjoyed this video, please subscribe. Also, check out our other videos and check out our other videos on our YouTube channel.