|6th Century Roman infantry officer.
The Roman Re-Conquest of North Africa (533 - 534 AD)
The Germanic tribe called the Vandals had conquered Roman North Africa in 439 AD. They also controlled the islands of Corsica, Sardinia and the Balearics.
The Vandals were fearsome warriors having spread terror wherever they went. In 455 they sacked Rome itself sending shock waves through the ancient world.
In 468 AD the Eastern Roman Empire tried to take back Africa in the Battle of Carthage only to fail.
The Romans called them barbarians even though they had become somewhat Romanized. They had adopted Arian Christianity. Very little is known about the Vandalic language itself, which was of the East Germanic linguistic branch. The Goths have left behind the only text corpus of the East Germanic language type: a 4th-century translation of the Gospels. All Vandals that modern historians know about language is they were able to speak Latin, which also remained the official language of the Vandal administration.
But Romanized or not, the Emperor Justinian wanted their lands for himself.
|Roman Carthage in Tunisia.
Background to Invasion: The Emperor Justinian was determined to drive out the barbarian invaders holding the western provinces of the Roman Empire. The obstacles were enormous and after the disastrous fiasco of 468, and he needed someone to successfully lead the army in this new invasion. A young general from Thrace named Belisarius had just made a name for himself on the Eastern Front by defeating a Persian army nearly twice his size. Justinian felt he had found his man.
Finding a general was only the fist step. Justinian was responsible for defending an incredibly long border against many enemies. The main enemy at the moment was the Persian Empire. For the first five years of his reign Justinian reluctantly waged a costly and unprofitable war against the Persians. The victory by Belisarius at Dara (and a truck load of gold) helped in negotiating (or at least buying) the "Endless Peace" with the Persians. Now eastern regiments were freed up for the invasion of Africa.
Video: Roman - Byzantine North Africa
The Roman provinces of North Africa were very important to the Empire. Africa provided tax revenue, trade and food exports to support the rest of the Empire. Re-capturing these provinces was a high priority for Emperor Justinian.
|The Emperor Justinian and his court.
Justinian's advisors were solid in their opposition to the campaign. From a military point of view they felt it was folly to send an invasion fleet of heavy transport ships over 1,000 miles from its' home base into enemy controlled waters, and then to land an outnumbered army (with no reinforcements available) to attack entrenched land forces. In addition the fleet could only sail in the summer calm of May to November. The autumn and winter storms would leave the army cut totally cut off. The finance ministers warned of the huge drain on the treasury and pointed out how the failed attack in 468 nearly bankrupted the nation.
John of Cappadocia warned the Emperor that their land forces were already spread very thin: "Have you dragon's teeth to sow? Well, then, summon up twenty thousand swordsmen . . . Can they win their way past the Vandalic battle fleets? Let a miracle destroy the Vandals! What follows? Caesar, can your army master and hold a continent? . . . You undertake to besiege Carthage: by land, the distance is not less than one hundred and forty days journey; on the sea, a whole year must elapse before you can receive any intelligence from your fleet. If Africa should be reduced, it cannot be preserved without the additional conquest of Sicily and Italy. Success will impose the obligations of new labors; a single misfortune will attract the Barbarians into the heart of your exhausted empire." Justinian's answer was that God was on their side.
The Gathering of the Fleet: The Roman Empire was still the only world power. No other nation had the resources to assemble such a strike force. The logistics alone must have been a nightmare: 36,000 soldiers and sailors, some 6,000 horses, arms, engines, military stores, water and provisions to last for a three month voyage of over 1,000 miles.
|A wider view of the political divisions in Europe and Africa at the time of Justinian.
Procopius said of the invasion fleet: "And for the whole force five hundred ships were required, no one of which was able to carry more than fifty thousand medimni, nor any one less than three thousand. And in all the vessels together there were thirty thousand sailors, Egyptians and Ionians for the most part, and Cilicians, and one commander was appointed over all the ships, Calonymus of Alexandria. And they had also ships of war prepared as for sea-fighting, to the number of ninety-two, and they were single-banked ships covered by decks, in order that the men rowing them might if possible not be exposed to the bolts of the enemy. Such boats are called "dromones" by those of the present time; for they are able to attain a great speed. In these sailed two thousand men of Byzantium, who were all rowers as well as fighting men; for there was not a single superfluous man among them."
At the harbor of Constantinople the navy brought together from Egypt, Cilicia and Ionia some 20,000 sailors and 500 transports ranging from 30 up to 500 tons. The proud galleys of old that had made the Mediterranean a Roman lake were long gone. Protecting the fleet were only 92 light brigantines.
Army regiments were withdrawn from the Eastern Front courtesy of the "Endless Peace" with Persia. About 10,000 infantry from Thrace and Isauria marched to Constantinople. Another 5,000 excellent cavalry were assigned. There were two additional bodies of Allied Troops: 600 Huns and 400 Heruls, all mounted horse archers.
|A Byzantine dromone.
The strike force of the Eastern Romans was the cavalry. They had adopted the metal stirrups invented by the Huns. This made the cavalry an effective shock force that could charge pell-mell with no fear of falling off. They also adopted from the Persians the "Cataphract." This was a horse and rider in armor. The cataphracts were skilled archers. They made initial assaults from a distance with their armor making them almost invulnerable to enemy fire. When the enemy fell into disorder the horsemen could close in for the kill. The Vandals and Goths did not copy this method of warfare. The cataphract was much more than just a horse, a bow and some armor. It took long years of training for a man to be able to control his horse with his knees while aiming his bow in any direction at full gallop.
In supreme command of both the navy and the army was Belisarius. Justinian granted Belisarius the title of Autocrator with almost boundless power to act as if the Emperor himself were present. In June 533 the fleet was ready. The Emperor and the Patriarch went in procession down to the docks. Icons waved behind them while marching choirs sang "Rex gloriae, Domine virtutum . . . King of Glory, Lord of armed hosts . . . " The Patriarch offered prayers for the success of the expedition. Most of those who witnessed the sailing felt that they would never return.
Small as the forces looked on paper this was a major effort by the Empire. Failure could do serious damage to the defense of the nation. At the very best the Eastern Roman's army and navy numbered no more than 150,000. The hard core professional battlefield regiments was a much smaller number. The force of 36,000 committed to the invasion amounted to 24% of their armed strength. No more troops could be committed without leaving their huge borders defenseless.
Smoothing the Way: Facing the Romans would be a Vandal land force of perhaps 30,000 plus a large fleet. The Emperor recognized that diplomacy was a vital ingredient to a successful invasion. Perhaps a revolution or two would draw Vandal attention and troops from the main attack. He encourage a rising of Pro-Roman factions in Tripolitana with a small military force and successfully drove out the Vandals.
|Roman Amphitheatre of El Jem, Tunisia
The 3rd biggest amphitheater known to man, so impressive that they filmed Russel Crowe’s Gladiator here. It could hold up to 35,000 people. Built in 300AD.
Justinian urged the Vandal governor of Sardinia to rebel, which he did. There was also a dynastic quarrel among Vandals. Gelimer had deposed Hilderic as king three years before and was keeping him and a few supporters as prisoners. Justinian also used a dispute between the Goths of Italy and the Vandals to his advantage. The Goths granted the Romans permission to dock their invasion fleet in Sicily on the way to Africa.
Vandal King Gelimer reacted to the revolutions just as Justinian had hoped. The King dispatched his brother Zano with 5,000 soldiers and 120 galleys to re-capture Sardinia. Now there would be no Vandal fleet nearby to attack the Roman troop transports when they were at their most vulnerable and a large part of the army would be wasted on a distant island. What's more, by making no attempt to recover Tripolitana, Gelimer ensured that if a Roman army made it to Africa they would be landing on a somewhat more friendly soil.
The Invasion: It was vital to keep the large fleet together. Procopius said, "The sails of the three ships in which he (Belisarius) and his following were carried he painted red from the upper corner for about one third of their length, and he erected upright poles on the prow of each, and hung lights from them, so that both by day and by night the general's ships might be distinguishable; then he commanded all the pilots to follow these ships. Thus with the three ships leading the whole fleet not a single ship was left behind."
Belisarius was granted a Roman triumph
(the last ever given) when he returned to
Constantinople. He was also made consul of
the Roman Empire in 535, one of the last
individuals ever to hold this office.
The fleet suffered thirst having been becalmed for 16 days. An additional 500 men died from disease. Finally after many weeks they were able to dock at Caucana on the southern shore of Sicily where Gothic officers had been ordered to help provision the Roman troops.
Belisarius was at a loss how to proceed. He had no idea where the Vandal navy and army was deployed. His own soldiers were openly afraid of the military legend of Vandal power. Procopius reports that men in the Roman navy talked of turning their ships fleeing if Vandal ships approached. While soldiers in the army said if they made it to dry land they would "try" to be brave against the enemy.
Belisarius sent Procopius, his adviser, to Syracuse to gather intelligence on the Vandal's movements. In entering Syracuse, Procopius ran into a fellow Roman and childhood friend who was engaged in the shipping business. He discovered that the Vandal King Gelimer had reacted to the two revolutions just as Justinian had hoped.
Tripolitana was too far away for the Vandals and the Romans in Egypt could easily support that revolt. So the King had just dispatched his brother Zano with 5,000 soldiers and 120 galleys to re-capture Sardinia. Now there would be no Vandal fleet nearby to attack the Roman troop transports when they were at their most vulnerable and a large part of the army would be wasted on a distant island.
Video: Carthage, North Africa
Today we see only the ruins of a great civilization. At the time of the invasion by Belisarius, these Roman cities and buildings would have been alive with merchants, farmers, teachers, soldiers, churches and more.
Procopius rushed back to Belisarius with the news. The general urged everyone to speed the operation. The fleet set sail again, passed Malta, and finally dropped anchor 5 days south of Carthage.
Before landing Belisarius had a council or war with some of his generals. They urged that they sail straight for Carthage and surprise it. Belisarius overruled this view. No one knew the exact location of the Vandal fleet. With the disaster of 467 A.D. in mind he felt is was better to get on dry land without delay.
Making Camp in Africa: Some three months after their departure from Constantinople the army and its' supplies safely made it to shore. The fleet was formed into a semicircle with five bowmen stationed on each ship as a guard. The rest of the army built a camp on the sea shore "which they fortified, according to ancient discipline, with a ditch and rampart.," and a stockade was also completed and the pointed stakes were fixed in place all around.
|Outline of a traditional Roman fort. Being deep inside enemy territory, Belisarius made sure his men and their supplies were protected by building the standard Roman fortifications while on the march to Carthage.
On the next morning Belisarius awoke to find neighboring gardens pillaged by his troops. He inflicted strong corporal punishment on the men involved and then sharply rebuked the offenders saying: "This using of violence and the eating of that which belongs to others seems at other times a wicked thing only on this account, the Libyans, being Romans from of old, are unfaithful and hostile to the Vandals, and for this reason I thought that no necessaries would fail us and, besides, that the enemy would not do us any injury by a sudden attack. But now this your lack of self-control has changed it all and made the opposite true. For you have doubtless reconciled the Libyans to the Vandals, bringing their hostility round upon your own selves."
Belisarius imposed s rigid discipline which soon resulted in the natives selling all supplies possible to the Romans.
The capture of Syllectus: Procopius said, "The city of Syllectus was distant one day's journey from the camp, lying close to the sea on the road leading to Carthage, and that the wall of this city had been torn down for a long time, but the inhabitants of the place had made a barrier on all sides by means of the walls of their houses, on account of the attacks of the Moors, and guarded a kind of fortified enclosure; he, accordingly, sent one of his spearmen, Boriades, together with some of the guards, commanding them to make an attempt oh the city, and, if they captured it, to do no harm in it, but to promise a thousand good things and to say that they had come for the sake of the people's freedom, that so the army might be able to enter into it. And they came near the city about dusk and passed the night hidden in a ravine."
"But at early dawn, meeting country folk going into the city with waggons, they entered quietly with them and with no trouble took possession of the city. And when day came, no one having begun any disturbance, they called together the priest and all the other notables and announced the commands of the general, and receiving the keys of the entrances from willing hands, they sent them to the general."
|Roman Cavalry from the 6th Century.
The March to Carthage: Belisarius began the 10 to 12 day march to Carthage along a Roman road that followed the coast. He sent out 3 miles ahead of the main army 300 horse of his own guard under John the Armenian as advanced scouts. If John should see anything of the enemy he was to report it with all speed, so that the main force would be ready for battle.
The Allied contingent of 600 Huns were ordered to march the same distance to the left of the road to protect against a flank attack. The entire Roman fleet was instructed to sail within sight of the land forces to cover the right flank aganist the Vandal navy. The Roman infantry and remaining cavalry marched as a group shielded on three sides.
Belisarius had no worries about his rear. Tripolitana was controled by the Romans and the locals had been made friendly with kind treatment.
Procopius writes "when Belisarius reached Syllectus, the soldiers behaved with moderation, and they neither began any unjust brawls nor did anything out of the way, and he himself, by displaying great gentleness and kindness, won the Libyans to his side so completely that thereafter he made the journey as if in his own land; for neither did the inhabitants of the land withdraw nor did they wish to conceal anything, but they both furnished a market and served the soldiers in whatever else they wished. And accomplishing eighty stades each day, we completed the whole journey to Carthage, passing the night either in a city, should it so happen, or in a camp made as thoroughly secure as the circumstances permitted.
"Thus we passed through the city of Leptis and Hadrumetum and reached the place called Grasse, three hundred and fifty stades distant from Carthage. In that place was a palace of the ruler of the Vandals and a park the most beautiful of all we know. For it is excellently watered by springs and has a great wealth of woods. And all the trees are full of fruit; so that each one of the soldiers pitched his tent among fruit-trees, and though all of them ate their fill of the fruit, which was then ripe, there was practically no diminution to be seen in the fruit."
The Vandals React: News of the invasion reached King Gelimer and put the Vandals in a panic. A Roman army had suddenly appeared out of nowhere and was within a few miles of Carthage itself. It was the last thing he had expected. The King needed to prolong the war as long as possible until his brother could return from Sardinia with the army and fleet.
Gelimer sent word to kill the old king who was a prisoner and all the others connected with him either by birth or otherwise. The Vandals quickly mobilized what troops were at hand for battle.
The Battle of Ad Decimum (or Ten Mile Post)
Unfortunately the Vandals had destroyed, or allowed to decay, many of the old fortifications of the Romans leaving the King only two options: abandon Carthage or engage in battle on open ground.
King Gelimer chose to fight at the ten mile mark outside of the city called Decimum. At that point the coast road turns inland and the Romans would be separated from their fleet.
The Vandal Battle Plan: Even though seriously pressed for time, Gelimer came up with an excellent battle plan. The King knew that the Romans would have to leave their fleet behind them as Belisarius turned away from the coast at the Lake of Tunis.
So Gelimer divided his quickly thrown together army of perhaps 10,000 men into three forces. A smaller force under his brother Ammatas would march to the defile of Decimum some ten miles from Carthage just below Tunis. There they would try to hold the position against the Roman advanced guard. A second force under the King's nephew Gibamund with 2,000 men would march across a salt plain southwest of Tunis to strike the Roman left flank.
The main Vandal cavalry force under Gelimer with 7,000 men would make a wide sweep to the south around the entire Roman army and hit them in the rear. The Romans would be out of reach of their fleet and pinned with their backs against the Lake of Tunis by three Vandal armies.
It was a bold plan. But plans never survive first contact with the enemy.
|First phase, the Roman advance parties defeat
the Vandal flanking detachments.
|Vandal and Alan warriors.
The Vandal Holding Force: When the Romans bivouacked in Grasse, scouts coming from both armies met each other, and after an exchange of blows they each retired to their own camp. Both sides were now aware the enemy was not far away. As the Romans marched from there it became impossible to discern their ships at sea.
The Vandal holding force under Ammatas never came together properly. Ammatas made a serious error by showing up at the Decimum defile hours ahead of time with only a few men. The rest of his troops were strung out in small groups of 20 to 30 men each on the road from Carthage. While surveying the ground Ammatas ran into John the Armenian's troop.
Ammatas was a brave warrior and killed by his own hand 12 of John's best men before he himself was slain. After Ammatas fell the Vandals, fleeing at top speed, swept back all those who were coming from Carthage to Decimum.
John's men gave chase right up to the city gates leaving a 10 mile trail of large numbers of dead Vandals.
March on the Roman Left Flank: Gelimer had commanded his nephew Gibamund to take 2,000 Vandals and march through a salt plain south of Tunis and attack the Roman left flank.
If Belisarius had not arranged his forces with John to take the lead, and the 600 Huns to march on the left of the army, the Romans would never have been able to escape the Vandals.
Gibamund and his two thousand Vandals came to Pedion Halon, which is forty stades distant from Decimum on the left as one goes to Carthage. It is destitute of human habitation or trees or anything else, since the salt in the water permits nothing except salt to be produced there. In that place they encountered the Huns and were all destroyed.
The Vandals had no experience of battle with the Hun, but heard that the nation was very warlike. They were terrified at the danger. Though outnumbered 3 to 1, when the Hun cavalry charged the Vandals could not withstand them. They broke ranks and ran and never thinking of resistance. The Vandals were all disgracefully destroyed and Gibamund killed.
Video: Byzantine Cavalry
|Second phase, King Gelimer routs the Roman foederati.
King Gelimer's Attack from the South: Belisarius knew nothing at all of what had happened with John's advanced guard. But seeing a place well adapted for a camp some thirty-five stades distant from Decimum, he surrounded it with a stockade which was very well made, and placing all the infantry there.
Belisarius made a speech to his troops. He was fearful of going directly to the enemy stronghold of Carthage. But he pointed out the advantages the Romans had. The Romans had fought many wars with Persians and Scythians.
The general said, ". . . but the Vandals, since the time they conquered Libya, have seen not a single enemy except naked Moors. And who does not know that in every work practice leads to skill, while idleness leads to inefficiency? Now the stockade, from which we shall have to carry on the war, has been made by us in the best possible manner. And we are able to deposit here our weapons and everything else which we are not able to carry when we go forth; and when we return here again, no kind of provisions can fail us."
Belisarius did not want to risk the entire army at this point in the campaign. He left the infantry and supplies in the stockade and took the cavalry on the road.
Gelimer had followed Belisarius at a safe distance, but the hilly nature of the terrain did not allow him to see the movements of the Romans nor the disaster to the Vandals on his left.
There was a brief skirmish between the Roman Foederati and the vanguard of the Vandals. The Foederati fled for about a mile down the road where they met up with another 800 Romans. Seeing the Foederati galloping toward them in disorder they joined the panic and rode back to the main force.
|Third phase, the final clash between Belisarius and Gelimer.
Victory was now within reach of Gelimer. The historian Procopius personally witnessed the terror of the fleeing Roman cavalry. "Had Gelimer pursued immediately," said Procopius, "I do not think that even Belisarius would have withstood him, but our cause would have been utterly ruined, so large appeared the multitude of the Vandals and so great the fear they inspired; or if he had made straight for Carthage he would have slain easily all the men with John, and would have preserved the city and its treasurers, and would have taken our ships which had approached near, and deprived us not only of victory but of the means of escape."
Instead Gelimer descended from the hill at a walk, and when he reached the level ground and saw the corpse of his brother. He became completely unmanned and expressed loud lamentations. Rather than pursue the fleeing Romans, he could only think of burying the corpse of his family member.
Meantime Belisarius, meeting the fugitives stopped their flight, and arrayed them all in order and rebuked them at length; then. After hearing of the death of Ammatas and the pursuit of John, and learning what he wished concerning the place and the enemy, he proceeded at full speed against Gelimer and the Vandals.
The Vandals believing the fighting was at an end had dismounted and were inspecting the battlefield while Gelmer arranged funeral rites. Belisarius charged the barbarians bringing with him a large cloud of drifting dust that gave the impression of a much larger Roman force. The Vandals could not withstand the onset of the Romans, but fled with all their might, losing many men. The battle only ended at nightfall.
Procopius reported, "Now the Vandals were in flight, not to Carthage nor to Byzacium, whence they had come, but to the plain of Boulla and the road leading into Numidia. So the men with John (the Armenian) and the Massagetae (Huns) returned to us about dusk, and after learning all that had happened and reporting what they had done, they passed the night with us in Decimum.
|An older view of Carthage.
The Capture of Carthage: Procopius says, "But on the following day the infantry with the wife of Belisarius came up and we all proceeded together on the road toward Carthage, which we reached in the late evening; and we passed the night in the open, although no one hindered us from marching into the city at once. For the Carthaginians opened the gates and burned lights everywhere and the city was brilliant with the illumination that whole night, and those of the Vandals who had been left behind were sitting as suppliants in the sanctuaries."
"But Belisarius prevented the entrance in order to guard against any ambuscade being set for his men by the enemy, and also to prevent the soldiers from having freedom to turn to plundering, as they might under the concealment of night. On that day, since an east wind arose for them, the ships reached the headland, and the Carthaginians, for they already sighted them, removed the iron chains of the harbour which they call Mandracium, and made it possible for the fleet to enter. . . . . There they arrived about dusk and all anchored, except, indeed, that Calonymus with some of the sailors, disregarding the general and all the others, went off secretly to Mandracium, no one daring to hinder him, and plundered the property of the merchants dwelling on the sea, both foreigners and Carthaginians."
"On the following day Belisarius commanded those on the ships to disembark, and after marshalling the whole army and drawing it up in battle formation, he marched into Carthage; for he feared lest he should encounter some snare set by the enemy. There he reminded the soldiers at length of how much good fortune had come to them because they had displayed moderation toward the Libyans, and he exhorted them earnestly to preserve good order with the greatest care in Carthage. For all the Libyans had been Romans in earlier times and had come under the Vandals by no will of their own and had suffered many outrages at the hands of these barbarians."
|Dougga / Thugga
This northern Tunisan town is known
as one of the best reserved
Roman towns in all of Africa.
"After such words of exhortation he entered Carthage, and, since no enemy was seen by them, he went up to the palace and seated himself on Gelimer's throne. There a crowd of merchants and other Carthaginians came before Belisarius with much shouting, persons whose homes were on the sea, and they made the charge that there had been a robbery of their property on the preceding night by the sailors. And Belisarius bound Calonymus by oaths to bring without fail all his thefts to the light. And Calonymus, taking the oath and disregarding what he had sworn, for the moment made the money his plunder, but not long afterwards he paid his just penalty in Byzantium. For being taken with the disease called apoplexy, he became insane and bit off his own tongue and then died. But this happened at a later time."
"But then, since the hour was appropriate, Belisarius commanded that lunch be prepared for them, in the very place where Gelimer was accustomed to entertain the leaders of the Vandals. This place the Romans call "Delphix," not in their own tongue, but using the Greek word according to the ancient custom. For in the palace at Rome, where the dining couches of the emperor were placed, a tripod had stood from olden times, on which the emperor's cupbearers used to place the cups."
"So Belisarius dined in the Delphix and with him all the notables of the army. And it happened that the lunch made for Gelimer on the preceding day was in readiness. And we feasted on that very food and the domestics of Gelimer served it and poured the wine and waited upon us in every way. And it was possible to see Fortune in her glory and making a display of the fact that all things are hers and that nothing is the private possession of any man. And it fell to the lot of Belisarius on that day to win such fame as no one of the men of his time ever won nor indeed any of the men of olden times."
" . . . . all the soldiers under the command of this general showed themselves so orderly that there was not a single act of insolence nor a threat, and indeed nothing happened to hinder the business of the city; but in a captured city, one which had changed its government and shifted its allegiance, it came about that no man's household was excluded from the privileges of the market-place; on the contrary, the clerks drew up their lists of the men and conducted the soldiers to their lodgings, just as usual, and the soldiers themselves, getting their lunch by purchase from the market, rested as each one wished."
| The Vandal Zano with 5,000 soldiers and
120 galleys was sent to re-capture Sardinia.
"Afterwards Belisarius gave pledges to those Vandals who had fled into the sanctuaries, and began to take thought for the fortifications. For the circuit-wall of Carthage had been so neglected that in many places it had become accessible to anyone who wished and easy to attack. For no small part of it had fallen down, and it was for this reason, the Carthaginians said, that Gelimer had not made his stand in the city."
To This Point: So far it had been a brilliant, almost textbook, military campaign.
The coast of Libya was in Roman hands. What is southern Tunisia up to and including the city of Carthage was now under Roman control. Belisarius had a solid base to work from, but the destruction of the Vandal Kingdom was far from over.
On the negative side, Belisarius was still very isolated from the Empire and any possible help. There were potential hostile Gothic kingdoms in Italy and Spain to consider.
The Vandals were damaged but undefeated. King Gelimer still had a large army under his command. The 5,000 Vandal troops in Sardinia had put down the pro-Roman revolt. Soon they would be joining Gelimer. With the two armies united and working on their home soil they could take on the victorious Roman army hold up inside Carthage.
But that is another story.
.History of the Wars, Books III and IV, Procopius of Caesarea
|6th Century Eastern Roman Cavalry