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Battle of Strasbourg
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The Battle of Strasbourg, also known as the Battle of Argentoratum, was fought in 357 between the Late Roman army under the Caesar (deputy emperor) Julian and the Alamanni tribal confederation led by the joint paramount king Chnodomar. The battle took place near Strasbourg (Alsace, France), called Argentoratum in Ammianus Marcellinus' account, Argentorate in the Tabula Peutingeriana (Section 2).
Although probably outnumbered by a substantial margin, Julian's army won a complete victory after a hard-fought struggle.
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The Battle of Strasbourg, also known as the Battle of Argentoratum, was fought in 357 between the Late Roman army under the Caesar (deputy emperor) Julian and the Alamanni tribal confederation led by the joint paramount king Chnodomar. The battle took place near Strasbourg (Alsace, France), called Argentoratum in Ammianus Marcellinus' account, Argentorate in the Tabula Peutingeriana (Section 2).
Although probably outnumbered by a substantial margin, Julian's army won a complete victory after a hard-fought struggle. With negligible casualties of their own, the Romans drove the Alamanni beyond the river Rhine inflcting heavy losses. Julian's force, the imperial escort army of Gaul, was small but high-quality. The battle was won by the skill of the Roman infantry, with the cavalry initially performing poorly.
The battle was the climax of Julian's campaigns in 355-7 to evict barbarian marauders from Gaul and to restore the Roman defensive line of forts along the Rhine, which had been largely destroyed during the Roman civil war of 350-3. In the years following his victory at Strasbourg, Julian was able to repair and garrison the Rhine forts and impose tributary status on the Germanic tribes beyond the border.
Sources
By far the most detailed and reliable source for the battle, and Julian's Gallic campaign (355-60) generally, is the Res Gestae (Histories) of Ammianus Marcellinus, a contemporary historian. Ammianus was a Greek career soldier who joined the army before 350 and served until at least 363. Enlisted as a protector (cadet senior officer), he served as a staff officer under magister equitum Ursicinus and then under Julian himself in the latter's Persian campaign. He had experience of the Gallic front as he was involved in the suppression of the revolt of Claudius Silvanus, the magister equitum in Gaul (355). His personal experience in the high command of the military of the time makes him a reliable and valuable source. However, his narrative shows him to be an admirer of Julian, occasionally descending to the level of eulogy. He may at times praise Julian's performance to excess, omit his failings, and show hostility to his enemies.
The late 5th century Byzantine chronicler Zosimus's Nova Historia deals with the battle, and Julian's Gallic campaign in a summary fashion and adds little to Ammianus' account. But Zosimus is useful because his account of the revolt of Magnentius (350-3) survives, unlike Ammianus', which is contained in the 13 lost books of his history.
The contemporary rhetorician Libanius delivered Julian's funeral oration (363). This contains some details which are missing in Ammianus, which he presumably learnt from members of Julian's entourage. But because his is a frank eulogy, not a historical narrative, his account of Julian's campaign is doubtful, and Ammianus' version is to be preferred where there is a contradiction.
The Alamanni
During the third century, the small and fragmented tribes of Germania Libera ("free Germany" i.e. Germany outside the empire) apparently coalesced into large, loose confederations: the Franks (NW Germany), Alamanni (SW Germany) and Burgundians (Central Germany). Although riven by internal feuding, these confederations could mobilise large forces and may have presented a greater threat to the empire than previously.
The Alamanni were a confederation of Germanic tribes who, originally from the Main valley of central Germany, had colonised the Agri Decumates (roughly the modern state of Baden-Württemberg in SW Germany) when it was evacuated by the Romans in the mid-3rd century after belonging to the Roman province of Germania Superior for over 150 years. The Alamanni established a series of territorially defined pagi (cantons) on the east bank of the Rhine. The exact number and extent of these pagi is unclear and probably changed over time.
Pagi, usually pairs of pagi combined, formed kingdoms (regna) which, it is generally believed, were permanent and hereditary. Ammianus describes Alamanni rulers with various terms: reges excelsiores ante alios ("paramount kings"), reges proximi ("neighbouring kings"), reguli ("petty kings") and regales ("princes"). This may be a formal hierarchy, or they may be vague, overlapping terms, or a combination of both. In 357, there appear to have been two paramount kings (Chnodomar and Westralp) who probably acted as presidents of the confederation and 7 other kings (reges). Their territories were small and mostly strung along the Rhine (although a few were in the hinterland). It is possible that the reguli were the rulers of the two pagi in each kingdom. Underneath the royal class were the nobles (called optimates by the Romans) and warriors (called armati by the Romans). The warriors consisted of professional warbands and levies of free men. Each nobleman could raise an average of ca. 50 warriors.
The total Germanic population of Alamannia at this time has been estimated at a tiny 120,000 - 150,000. This compares with ca. 10 million in Gaul. Alamanni society was a violent warrior-society based on feuding clans. This bred good fighters.
Background: Barbarian invasion of Gaul
In January 350, the Roman empire was ruled by two sons of Constantine I the Great, the Augusti (joint emperors) Constans, who ruled the West, and Constantius II in the East. But in that month, Constans was overthrown and killed by the usurper Magnentius, a laetus from Gaul who was comes (commander) of the elite brigade in Constans' comitatus (imperial escort army). In the East, Constantius had been engaged in a lengthy war against the Persians under Shah Shapur II (337-50). But he immediately concluded a truce in order to deal with Magnentius. He led his own comitatus to Illyricum where he assumed command of the local comitatus also, bringing his combined strike force to ca. 60,000. Magnentius gathered an army consisting of the Gaul comitatus and probably some Frankish and Saxon foederati (allies) and marched into Illyricum to confront Constantius. (For explanation of the term comitatus, see Late Roman army).
The Franks and Alamanni on the Rhine frontier now seized the opportunity presented by the absence of the best Roman forces in the civil war to overrun much of eastern Gaul and Raetia. Libanius claims that they were incited to do so by letters from Constantius, in order to create a diversion in Magnentius' rear. The barbarians captured many of the Roman forts along the Rhine, demolished their fortifications and established permanent camps on the West bank of the river, which they used as bases to pillage Gaul during the four years that the civil war lasted (350-3). In excess of 20,000 Roman civilians are believed to have been abducted from Gaul and forced to work in the Alamanni's fields. In turn, this would have reinforced Alamanni raiding in Gaul by freeing many from the harvest cycle.
Meanwhile, a huge number of Rome's finest troops, including most of the Gaul comitatus and perhaps half the combined Eastern/Illyricum force, were wiped out in the civil war. At the Battle of Mursa in Pannonia (351), one of the bloodiest in Roman history, Magnentius lost an estimated 24,000 men (perhaps two-thirds of his army). Constantius' army, although victorious, suffered even greater casualties (ca. 30,000).. A final encounter at the Battle of Mons Seleucus in the Alps saw further casualties. Such massive losses of first-grade troops could not quickly or easily be replaced. Constantius, now based in Milan, was left with an escort army of about 30,000, but Illyricum and the East had been stripped of their comitatus. With renewed Persian attacks, the East was the top priority for reinforcement and Illyricum second. In the circumstances, Constantius could only spare in the region of 13,000 men for the Gaul comitatus, about half its previous strength, and appointed the Frankish-born general Silvanus as its commander (magister equitum).
Using his own comitatus, Constantius succeeded in driving the Alamanni out of Raetia (354), and binding the kings of southern Alamannia, Wadomar and Gundomad, with a treaty of alliance. Meanwhile, Silvanus made considerable progress in restoring the situation in Gaul. But the following year (355), Silvanus staged a coup d'état, proclaiming himself emperor at Colonia (Cologne). He was swiftly eliminated by a team of senior officers (which included Ammianus) despatched by Constantius under the leadership of Ursicinus, who replaced Silvanus as magister equitum. But the shaken emperor decided that he needed a member of his own Flavii (Constantinian) clan to share the burdens of governing the empire, a remarkable change of policy for a ruler who regarded all his relatives with intense suspicion and had put most of them to death. He appointed his cousin Julian as Caesar (deputy emperor) for the West and gave him overall command of forces in Gaul. The appointment was widely seen as unsuitable as Julian, who was just 23 years old, had no military experience and until that moment had spent his time studying philosophy at Athens. But Constantius' own paranoid purges had left him little choice: Julian was his sole surviving adult male close relative.
The task confronting Julian as he took up his command was daunting. The civil war had left Gaul in a chaotic state. The defensive line of the Rhine had largely collapsed. According to Ammianus, the Franks had taken Cologne by storm and razed it to the ground. Moguntiacum (Mainz), Borbetomagus (Worms), Nemetae Vangionum (Speyer), Tabernae (Saverne), Saliso (Brumat) and Argentorate (Strasbourg) were all in German hands. Only three strongpoints on the Rhine remained in Roman hands: a single tower near Cologne and two forts, at Rigodunum (Remagen) and Confluentes (Koblenz). Large barbarian bands were roaming and pillaging eastern Gaul at will, reaching as far as the river Seine. So many and so large were the marauding enemy bands that Silvanus was considered a brave man for having led 8,000 men along a wooded highway in the heart of Gaul because of the risk of ambush. Further, the limitanei (border protection forces) along the Rhine had been decimated by the fall of most of their forts to the Germans, while those units that survived intact had mostly retreated from the frontier to garrison Gaul's cities. Cynics at court whispered that Julian had been given an impossible mission to rid Constantius of a potential rival for the throne. In the event, however, he surprised everyone by proving to be an effective military leader.
Prelude
Julian, who was given by Constantius a small escorting force including 200 scholares, a regiment of cataphracti and some mounted archers (total ca. 1,200 men), set out from Milan for Gaul. When he reached Taurini (Turin), he received the calamitous news that Cologne had fallen to the Franks. He spent the winter of 355/6 with his escorting troops at Vienna (Vienne), not far South of Lugdunum (Lyon). For the 356 campaigning season, Julian's first task was to link up with the main Gaul comitatus, which had wintered at Remi (Rheims) under the command of the magister equitum, Ursicinus' recently-appointed successor, Marcellus. This involved a long march through country swarming with Alamanni raiding bands, many of which were as large as Julian's own escort and expert at ambuscades. On the way, Julian surprised and drove off a large barbarian force that was besieging Augustodunum (Autun) and defeated a raiding band in the Morvan wilderness.
At Rheims, Julian showed his characteristic boldness by deciding, in conference with his senior commanders, to deal with the Alamanni problem at source by marching straight to Alsace and restoring Roman control of the region. At Decem Pagi (Dieuze), however, his army was ambushed and nearly destroyed by a large German band who fell on two legions in the rearguard which had lost contact with the rest of the column in dense mist. They were rescued by auxilia palatina regiments that heard the uproar. Proceeding to Brotomagus (Brumath) in Alsace, Julian's army routed a German band in the field. But, after assessing the situation in Alsace, with all the Rhine forts ruined and in enemy hands, Julian decided that his force was insufficient to prevail over the Alamanni alone. Instead, he set out to recover the critical lower Rhine city of Cologne, which had been destroyed by the Franks. From Metz, he led his army via Treviri (Trier) to Koblenz and thence along the Rhine to Cologne (the forts in this sector of the Rhine were still in Roman hands). Entering the ruined city unopposed, Julian's men were the set to work to rebuild the city walls. Julian then concluded a peace treaty with the Franks. This had the important effect of removing half the opposition from the equation and allowing Julian to focus his resources on dealing with the Alamanni.
For the winter of 356/7, he chose Senones (Sens) near Paris as his base, but quartered many troops in other towns to spread the burden with a large body at Rheims under Marcellus. A large band of Alamanni heard of his reduced escort, however, and besieged him at Sens. Julian's forces were able to hold out until, after a month, the Germans withdrew. He was so outnumbered by the enemy, however, that he was unable to sally forth and give chase. During the siege, Marcellus had failed to come to his assistance. For this omission, denounced as cowardice by Ammianus, Marcellus was dismissed as magister equitum by Constantius and replaced by Severus, a distinguished officer who was more compatible with Julian.
For the 357 campaign season, a plan was laid down at Constantius' headquarters in Mediolanum (Milan) to trap the Alamanni in eastern Gaul in a pincer movement. Julian would advance eastward from Rheims, while the major part of Constantius' comitatus in Italy (25,000 strong) was despatched under magister peditum (field marshal) Barbatio to Augusta Rauracorum (Augst) in Raetia, from which he was to advance northward to meet Julian. The Alamanni bands would be cornered and destroyed in the southern part of Germania I province (Alsace).
But large bands of Alamanni, ignoring the threat posed by the Roman manoeuvre, invaded and ravaged the rich Rhone valley, even trying to take the major city of Lugdunum (Lyon) by assault. The attack was repulsed as the walls of the city proved too strong and the garrison, presumably limitanei troops, too valorous. Nevertheless, the Germans had devastated a large area and taken vast amounts of booty.
However, the Germans were now trapped in the interior of Gaul with their way back to the Rhine barred by the Roman armies. In Julian's sector, the Caesar despatched squadrons of cavalry to lie in ambush on three roads and these successfully intercepted and destroyed the returning barbarian bands. But in Barbatio's sector, the Germans were allowed to pass unmolested. Barbatio's chief-of-staff Cella rejected the urgent request of two of his cavalry tribuni (regimental commander) Valentinianus (later emperor Valentinian I, ruled 364-5) and Bainobaudes to deploy their squadrons on a highway that they expected the enemy would use. The escaping force reached some islands in the Rhine near Strasbourg where the raiding-bands had moved their camps for safety in response to the Roman pincer movement. Nevertheless, Julian pursued them vigorously. Although without boats, his men succeeded in reaching one island, as the river which had become fordable at some points due to summer drought. An entire raiding-band was surprised and slaughtered, a success repeated on a few other islands. In response, the Germans evacuated the remaining islands, removing their sutlers, baggage and booty to the far side of the Rhine.
Julian now turned his attention to rebuilding the fortress at Saverne, which had been destroyed by the Alamanni. Saverne lay astride the Mediomatrici (Metz) - Strasbourg Roman highway, at the mouth of the main entry route through the Vosges mountains into northern Alsace. Its strategic location, and commanding heights overlooking the Rhine valley, explains why it was a priority for Julian. While this work was proceeding, at some distance (probably in the vicinity of Strasbourg), the vanguard of Barbatio's army was attacked by surprise by a large barbarian force as it approached the camp of Julian's deputy, Severus, who was apparently operating separately from Julian. The vanguard fled in disarray, and instead of fighting, the rest of Barbatio's force disengaged and hastily retreated, closely pursued, out of Alsace and a good way into Raetia, losing most of their sutlers, pack animals and baggage. At this point, Barbatio, whose cooperation with Julian had been grudging at best, withdrew his army from the theatre of operations altogether, without Julian's permission. He sent his forces across the Alps into winter quarters in Italy, despite it still being only the midpoint of the campaigning season and the Alamanni far from defeated or ejected from Alsace. This reduced Roman forces in Alsace by two-thirds and effectively sabotaged the pincer strategy. Ammianus states that it was unknown whether Constantius was behind Barbatio's actions, but it seems unlikely that the magister would have risked ceasing operations unless confident of the emperor's approval.
At this time, the Alamanni confederation appears to have been under the presidency of two paramount kings, Chnodomar and Westralp. But Chnodomar was the driving force. A man of prodigious stature, strength and energy, he was nicknamed Gigas ("the Giant") by the Romans. He was a formidable sight in his "flashing" helmet (probably gold-leafed) and full parade armour. He is described by Ammianus as the "evil mastermind" behind the invasion of Gaul.
Chnodomar could not ignore Julian's fortification of Saverne, as it threatened his control of Alsace and blocked his main access route into the interior of Gaul. He had come to see this region as Alamanni territory by right of conquest after occupying it for several years. He also claimed to possess letters from Constantius granting the Alamanni the right to occupy those lands. Chnodomar had been surprised and dismayed by Julian's successful campaigns of 355-7. But he was encouraged by his own success against Barbatio and the intelligence brought to him by a deserter that Barbatio's withdrawal had left the Caesar with only 13,000 men. Having driven two Roman magistri from the field (Barbatio and before him, Magnentius' lieutenant, Decentius), Chnodomar had lost the barbarians' traditional fear of pitched battles with the Romans.
The Alamanni high kings now ordered a mass mobilisation of all the confederation's member tribes, gathering their disparate bands at Strasbourg. In addition, they received the timely support of the two Alamanni tribes near Raetia that had been pacified by Constantius in 355. Their leaders were overthrown in an anti-Roman coup by their optimates. Gundomad was slain and Wadomar forced to break his treaty and lead his warriors to join Chnodomar. Finally, they summoned the assistance of certain non-Alamanni tribes (probably Burgundians), partly for services rendered in the past, partly for payment. At Strasbourg on the Rhine (about 32km SE of Saverne), they gathered a combined force of some 35,000 men, according to Ammianus. This figure may be an exaggeration, but the exceptional size of the levy is shown by the presence of all the Alamanni kings and the report that German bands were crossing the Rhine to Strasbourg continuously for three days and nights. Their aim was to bring Julian to battle and crush him by sheer weight of numbers. They provoked Julian by sending him an insolent ultimatum to evacuate Alsace immediately.
Julian was now faced with a finely-balanced judgement call. The safer option was to ignore Chnodomar's challenge and to keep his forces in their fortified bases and request and await reinforcements, if necessary until the following year's campaign season. But the performance of Barbatio and the imperial comitatus in the recent campaign cast doubt on whether such reinforcements would be supplied and on their value if they were. Such a course would also expose Gaul to a massive Germanic invasion just when the harvest was due. Alternatively, he could fight Chnodomar alone. This offered the prospect of a decisive victory, since the Alamanni forces were now, unusually, concentrated and not divided into many disparate bands. This argument was strongly made by Florentius, the praefectus praetorio Galliarum (governor-general of Gaul), who had the crucial job of ensuring the army's supplies. The Romans almost always won pitched battles with barbarians, because of their superior equipment, organisation and training. But in this case it was clearly a high-risk option because of the Germans' massive superiority in numbers. Nevertheless, Julian decided to give battle.
The adversaries compared
Numbers
According to Ammianus, a deserter informed Chnodomar that Julian had 13,000 men with him at Saverne. But this leaves open the possibility that he may have summoned more to join him for the battle. It is possible that Severus' division was additional, as it is stated that while Julian was at Saverne, Severus' men occupied a separate camp near Barbatio's army. Libanius implies that Julian had 15,000 men under his command. If this was true, the additional 2,000 may have been Severus' division. Also, Julian may have been able to call on some limitanei units to assist him. Zosimus states that on arrival in Gaul, Julian set about a major recruitment drive. This was presumably in order not only to fill vacancies in his comitatus units, but mainly to reconstitute limitanei regiments that had largely dissolved during the years of anarchy. Julian's force may therefore had numbered slightly more than 15,000.
At the same time, some historians regard Ammianus' figure of 35,000 for the Alamanni forces as unrealistically high. It has been recently suggested that in reality the Alamanni at Strasbourg may have been only ca. 15,000, much the same as the Romans. This calculation is based on the assumption that the average size of Alamanni raiding groups (800 men) represented the maximum manpower of a pagus. In Ammianus' favour, it should be noted that the Strasbourg figure is consistent with two other figures given for Alamannic armies elsewhere in his history: an army of 40,000 in 378; and in 366 an army divided in three, with one division 10,000 strong. But the population estimate for Alamannia provided by modern archaeology (120-150,000 individuals) suggests that Ammianus' figure is probably too high. 35,000 would represent the maximum warrior element of such a population (calculated at 25% of the total). This would leave noone behind to guard their home pagus or to allow for sickness or absence. In practice, it is unlikely that even a full levy such as the one apparently ordered by the Alamanni high kings could have raised more than two-thirds of the maximum, i.e. 22,000 men. To these, however, should be added the non-Alamanni allies, whose number is unknown. A further indicator is the size of forces considered necessary by the Roman government to deal with the Alamanni threat in Gaul: 40,000 (Julian's 15,000 plus Barbatio's 25,000). Assuming that the Roman military planners would have sought a 2 to 1 superiority to guarantee success, that would imply an Alamannic strength of ca. 20,000. On the basis of these indicators, the midpoint between the recent estimate and Ammianus' figure, 25,000, would seem plausible.
Overall, therefore, it is likely that the Romans were outnumbered by around 1.5 to 1 rather than the 3 to 1 that Ammianus implies. However, that the Romans were outnumbered at all seems likely, otherwise Chnodomar would probably not have risked a pitched battle In cavalry, however, Julian may have had a numerical advantage.
Quality
Julian's force, although relatively small, was of high quality, containing some of the best regiments in the Late Roman army, with an awesome combat reputation. All were palatini (top-grade regiments). A substantial proportion of his troops were of barbarian, mostly Germanic, birth. An analysis of known names of officers and men in the auxilia palatina infantry regiments suggests that anywhere between a third and a half of the effectives were barbarian (the Roman-born troops were mostly locally-recruited Gauls). Of the German-born recruits, many would probably have been Alamanni. But the history of Julian's Gallic campaign shows that his barbarian troops were fiercely loyal and reliable. It is true that there were a few isolated cases of Germanic deserters who defected to the enemy, but these were mostly motivated by personal reasons, not by ethnic solidarity. The only recorded instance of the latter was an officer who allegedly alerted members of his own tribe that Julian was planning a campaign against them. In the vast majority of cases, it is clear that regimental loyalties prevailed over ethnic ones. This is evidenced by the fierce alacrity of Julian's troops to engage with the enemy and the determination with which they fought the battle (3 of the 4 tribuni killed at Strasbourg had barbarian names).
Regarding training, the Roman troops were career professionals, constantly drilled in formation manoeuvres and combat techniques. Their most important advantage in a pitched battle was formation drill: the ability to hold one's position in a unit at regular intervals, and to replace fallen comrades, so that a unit maintains its shape and coherence as it moves or engages.
Chnodomar's men were of much less even quality. His best warriors were the professional retinues of the regales (royal class, called ring-givers by the Germans), organized in warbands. These consisted mostly of berserkers and long-haired swordfighters. They were well-equipped, as behove their masters' status. They wore little armour on purpose to ensure speed and, for the berserkers, power in doublehanded swordfighting (they wore their shield on their backs). The majority of his men, however, were temporary levies of little training, like all contemporary Germanic forces relying on light equipment and speed. On the Alamanni side, there is little evidence of formation manoeuvres. The professional retainers of the regales may have had some capacity for this. Ammianus' account mentions a globus (mass) of the best warriors coming together in the thick of the battle and breaking through the Roman line. In addition, several would likely have served in the Roman army in the past. But the majority of Chnodomar's men consisted of temporary levies, whose training was very limited. According to Ammianus, they had to rely on a crude frontal charge to try to break through by weight of numbers, and proved no match for the Romans in the final phase of the battle, a prolonged struggle of attrition at close-quarters.
Equipment
Roman military equipment was mass-produced in state-run fabricae ("factories") which brought together advanced forging technology and skilled artisans. Roman weapons were mostly made of internally produced steel such as chalybs Noricus which, although of far lower quality than the best contemporary steel made in Central Asia and China, was superior to unhardened iron. In contrast, forging technology, capacity and personnel were more limited in Germania libera, although there is evidence that production and standardization of equipment had greatly improved since the time of the Roman Principate. Steel-making was also known in Germania libera (spathae and rapier-like swords out of flexible steel were in use). But Alamanni production of sophisticated forge-products such as metal armour, helmets and swords was on a much smaller scale than the Romans'. Simple weapons such as axes and knives seem often to have been made of unhardened iron.
For personal protection, most Roman troops wore metal body armour (usually in the form a chain mail cuirass) and helmets, in addition to shields. In contrast, among the Alamanni, metal armour and helmets were probably owned by members of the social elite only. Most Alamanni foot soldiers had only shields and no metal armour or helmets.
For hand weapons, most Roman foot carried a thrusting-spear (hasta) and a sword (spatha). Among the Alamanni, spears were the universal weapon, swords were probably less common. Nobles (optimates) and the professional warrior-retainers of ringgivers certainly had them. For the lower ranks the position is not certain. Ammianus' report on the battle implies that many in the Alamanni ranks carried swords. Those that did not were armed with or saxes (long pointed knives) and axes.
For short-range missile (throwing) weapons, a Roman infantryman would probably had either a long throwing-spear or two or three short javelins (lanceae) and half a dozen plumbatae (weighted darts) with an effective range of ca. 30m. Ammianus talks of a variety of missiles being thrown by the Alamanni in the battle: spicula (a kind of long pilum-type javelin, also known as an angon), verruta missilia (short throwing-spears) and ferratae arundines (probably darts and franciscas: throwing-axes). Overall, there appears little difference in the throwing-missile capability of the contenders. Ammianus indicates that the Roman infantry ranks were obliged to hold their shields above their heads for much of the time due to the volume of missiles raining down on them.
One aspect of the line-up that Ammianus is silent about is long-range missile capability (archery). But it is highly likely that there were archers on both sides. On the Roman side, Ammianus attests one vexillatio of equites sagittarii (mounted archers) at Strasbourg. It is also likely that at least one regiment of foot archers took part, probably an auxilium of sagittarii (archers). There were thus probably ca. 1,000 archers in dedicated units on the Roman side. In addition, a number of ordinary infantry units probably included archers. The standard Roman bow was the recurved composite bow, a relatively compact weapon. Foot archers normally formed the rear rank of the Roman battle-line, shooting over the heads of their own infantry, whilst protected by it from the enemy.
Bows of various types were also used by the Alamanni. But the most common type, the yew longbow, could be a powerful weapon. As tall as its user, it could launch arrows with enough power to pierce armour. Such bows had been used in Northern Europe for centuries; it is believed that they became widespread in Germania libera in the 4th century. The longbow's long range made it suitable for shooting volleys from the rear over the heads of one's own infantry lines, but its size made it impractical to use in mêlées, or on horseback (for which the recurved bow was ideal). The archery capability of the Rhine Germans has traditionally been seen as negligible, due to the 6th century writer Agathias's comment that the Franks did not know how to use bows. But this is contradicted by the archaeological record and by Ammianus himself. Overall, the 4th century Roman soldier's equipment was superior to his enemy's, though probably not by the same margin as in earlier centuries.
Cavalry
The cavalry element of his force has been estimated at 3,000 (6 vexillationes - squadrons - of ca. 500 men each). This amounts to some 20% of the total force, a proportion in line with the late Roman army as a whole.
The size of Chnodomar's cavalry is unknown, but was probably a small proportion of the total, as the Alamanni's heavily forested land was not suited to large-scale cavalry operations. Most of the Alamanni horsemen were noblemen and their retainers, as only they could afford to keep a warhorse. They are unlikely to have represented a fifth of the force total as in Julian's army and were probably closer to the 7% cavalry contained in a Roman citizen legion of the mid-Republican period (320 - 90 BC), when the cavalry was levied exclusively from the wealthiest social class. A similar proportion of the Alamanni force of ca. 25,000 would total just 1,750 horse, probably brought up to around 2,000 by the non-Alamanni allies. Chnodomar's cavalry was thus probably significantly smaller, than the Romans'.
The Roman cavalry was also clearly superior to Chnodomar's in armour and training, as well as specialisation. The Romans deployed not only light, unarmoured cavalry like the Germans', but also semi-armoured (with mail cuirass) and heavily-armoured cavalry. The light cavalry consisted of one regiment of equites Dalmatae, a class of javelineers that appears to have been introduced only in the 3rd century, and one of mounted archers (equites sagittarii). These were fast, manoeuvrable horse who specialised in harassing attacks, pursuit and ambush. The heavily armoured horse were called cataphracti or clibanarii (these terms were probably interchangeable and did not indicate any significant difference in equipment). These were covered neck to toe in scale and/or lamellar articulated armour and were armed with a contus, a long heavy lance, as well as a sword. Since Ammianus implies at least two cataphracti regiments, they probably constituted about a third of the Roman cavalry (1,000).
Being of a wealthier class, most of Chnodomar's horsemen probably had swords, but lacked metal armour, although it is possible some of the Alamannic cavalry wore mail shirts captured from Roman troops when they overran the border defences. The Germans almost certainly did not have mounted archers, which were an Eastern speciality. Longbows are unsuitable for use on horseback.
Battle
The campaigning season was by now well-advanced, as Julian had spent a considerable time restoring Saverne. But it was still summer, as the weather was hot and wheat was ripe in the fields. It was therefore probably August. Julian's army covered the distance to Strasbourg in the morning, arriving within reach of the enemy at around noon. Chnodomar, alerted by his lookouts that the Roman army was in sight, moved his army forward from its base before the ruined walls of Strasbourg to his chosen battlefield nearby.
A short distance from the battlefield, Julian ordered his men to construct a fortified marching-camp. The latter had always been a fundamental feature of Roman campaign procedure, and was constructed at the end of each day's march. Ringed by a ditch and a stockade of sharpened wooden stakes, which was guarded day and night by patrols, the marching-camp provided basic protection for an army in the field, allowing troops to rest, refresh and sleep safe from the danger of surprise attack. When the army advanced to fight a battle, the camp, garrisoned by a small force left behind, provided a secure place to leave the army's sutlers, pack animals, supplies and baggage, as well as a refuge for survivors if the army was defeated. Concerned that his men might be too tired to fight after a long march in the hot sun, Julian proposed to his assembled troops to postpone the clash until the following day. But his officers and men would have none of it and clamoured to be led against the enemy that same day. Julian, who prided himself on acting by consensus, gave way. It was now around 3 o'clock in the afternoon (allowing three hours for constructing the camp, rest and refreshment). With only about 5 hours of good daylight left, this was late to start a battle, but would have the advantage that the barbarians, facing westwards, would be dazzled by the setting sun. Leaving any limitanei troops with them to guard the camp, the army advanced along the highway to the battlefield.
The battlefield was a gently-sloping hill a few miles from the Rhine, partly fields with ripe wheat. Libanius claims that on one side was an "elevated water course" (presumably an aqueduct or canal), built over a swamp. But this seems incompatible with Ammianus' statement that the battle took place on higher ground (as water could hardly flow uphill), and may be a garbled detail from another of Julian's battles. The site of the battlefield is dictated by Ammianus' statement that Julian's army marched 21 Roman miles (32 km) from Saverne along the Metz-Strasbourg highway. One leading theory is that the battle took place near the village of Oberhausbergen 3km NW of Strasbourg. The western edge of the battle field was defined by the highway, on the far side of which was broken, wooded ground impassable to cavalry.
Julian's best hope for a quick victory lay in a cavalry breakthrough. Not only was the German cavalry probably smaller than his own, but its lack of armour made it vulnerable to his armoured regiments, especially the cataphracts. If they could rout the enemy horse, his squadrons could then wheel and attack the German lines in the flank or rear, and the battle would be as good as won. Julian's cavalry would thus aim to deliver a shock charge, careering forward in a wedge formation with the cataphracts forming the spearhead, the conventional armoured cavalry on either side and the light regiments on the extreme right, ready to block outflankers and to pursue fleeing enemy horse. The initial collision would shatter the enemy formation, and then the Germans could be overpowered in the ensuing melee. Failing a cavalry breakthrough, Julian would have to rely on a struggle of attrition on foot, in which superior Roman armour, training and formation discipline would almost inevitably prevail.
The German host was waiting for the Romans, probably drawn up on the crest of the hill, to give Chnodomar's men the advantage of the slope. The German left wing was held by Chnodomar and his cavalry. Demonstrating that he was well aware of the threat posed by the Roman cavalry, Chnodomar had devised a stratagem. He interspersed lightly-armed infantry among his cavalry. These were easy to conceal in the standing grain. The idea was that in a mêlée, the foot soldiers would bring down the cataphracts by crawling along the ground and stabbing their horses in their underbellies, which were unprotected. The dismounted riders, weighed down by their armour, could then easily be despatched on the ground.The German right wing blocked the highway to Strasbourg, while in the woods beyond the highway were a substantial force of warriors hidden in ambush on Chnodomar's orders. The right wing was under his nephew Serapio (who was given his Greek name by his Hellenophile father). Although still a teenager, Serapio had already proved a military leader worthy of his uncle. The rest of the line was probably divided into pagi units under five major kings and ten petty kings.
Julian drew up his infantry was drawn up in two lines, widely spaced apart, each several ranks deep. This was a standard Roman line-up: the rear line troops were reserves who would be able to intervene if the enemy threatened to break through at any point, and to exploit opportunities as they arose. During the battle, the foot archers (sagittarii) would have formed the rear rank of the front line, to shoot over the heads of their own infantry. But at the start, archers were sometimes stationed in front of the main line, so that they could disrupt the enemy ranks with their missiles. This was especially likely if the Romans' archer forces were much stronger than the Chnodomar's, giving them a competitive advantage in a long-range missile exchange. But Ammianus does not state if this happened on this occasion. On the right wing was posted the entire cavalry. Most likely, the light cavalry would have been stationed in front, to harass the enemy before the heavy cavalry launched their shock charge. Set back from the left flank of the front line, Julian posted a separate division under Severus to face the woods beyond the highway, apparently with orders to advance into them, presumably to launch a surprise attack on the German right wing. Julian himself, with his escort of 200 scholares, probably took up position in the gap between the Roman lines, giving him a close, but relatively protected, view of the action.
As soon as the two armies were drawn up, a clamour arose from the German ranks, loudly demanding that Chnodomar and his entourage of chiefs should dismount and lead the main body of German foot warriors from the front. Chnodomar and the chiefs immediately complied. In so doing, Chnodomar forfeited any strategic control of the battle, as, trapped in the centre of the action, he would have no way of knowing what was happening in other sectors. Julian, on the other hand, maintained a detached position throughout (with his escort) and so was able to respond to events all over the field, such as the initial rout of his cavalry. It is unclear exactly where Julian was stationed but it was likely in the gap between the two Roman lines.
The Roman main charge would likely have been preceded by harassing attacks by the light cavalry. The mounted archers would execute what the Romans knew as the "Parthian attack": ride up to within range of the enemy, loose a volley of arrows, then hastily retreat, using the arrow distance to escape pursuit. This could be repeated several times, causing significant casualties and, ideally, enticing the enemy into a premature and disorganised charge. However, in this case, the German cavalry would have been prevented from charging as their interspersed infantry support would not have been able too keep up - most likely, they awaited the Roman cavalry at the halt, or moving forward slowly. The Roman heavy cavalry now charged the German horsemen. In the ensuing mêlée, Chnodomar's stratagem paid dividends. The interspersed foot warriors wreaked havoc, bringing down the horses of the cataphracts and then killing their riders on the ground. Unnerved by these tactics, and by the injury of one of their tribuni, the cataphracts panicked and fled the field. In their headlong flight, they crashed into the Roman infantry on the right, which, however, was able to maintain formation because of the skill of the crack auxilia palatina regiments Cornuti and Brachiati posted there. The cataphracts took refuge behind the infantry lines, where it took the personal intervention of Julian himself to rally them. Zosimus claims that one regiment of cataphracts refused to return to the fight and that after the battle, they were obliged by Julian to wear female clothes as punishment. The performance of rest of the cavalry is not described by Ammianus, but they would have been obliged to retreat with the cataphracts, though it is unclear whether they followed them to behind the infantry lines, or, more likely, halted to cover the Roman right wing. It is clear, however, that the German cavalry was unable to capitalise on their success to outflank the Roman right. Nevertheless, Chnodomar had trumped Julian's best card.
Encouraged by their cavalry's success, the foot soldiers in the German front line gave a great roar and ran towards the Roman line. In the centre, German foot warriors repeatedly charged the serried ranks of Romans, hoping to break through by sheer weight of numbers. But the Roman front line held for a long time, inflicting severe casualties on the Germans who flung themselves recklessly at their massed spears. Then, a group of German chiefs and their best warriors formed a dense mass, and, let through by the German front ranks, charged the Romans. This was probably a barbarian formation known as a "hogshead", a wedge protected by armoured warriors on the outside. They succeeded, by desperate efforts, in punching a hole through the centre of the Roman front line. This was potentially disastrous for the Romans. But despite being cut in two, the Roman front line evidently did not collapse: the experienced frontline regiments managed to hold their separated wings in formation.
In the meantime, on the Roman left wing, Severus must have suspected the prepared ambush, and held back from advancing into the woods. Libanius contradicts this, claiming that the Romans charged the enemy and flushed them out of their hiding places. But Ammianus' version is more likely, as the Romans would hardly have benefited by advancing straight into a prepared trap. Ammianus does not report further action in this sector. But it is likely that the hidden Germans eventually lost patience, advanced out of the woods and charged at Severus' division, only to be routed by Severus' crack troops.
Meanwhile, a large number of Germans poured through the breach and charged the centre of the Roman rear line. This position was held by the elite Primani legion, which stopped the German attack in its tracks and then counterattacked, routing the breakthrough. The breach in the front line was presumably filled, either by the separated wings of the front line reconnecting, or by the Primani from the rear line (Ammianus does not specify which). The front line, now extended on the left flank by the rear line left wing, (and presumably by Severus' victorious division), began pushing the Germans back, and gradually hemmed them in from the flanks. At this point, the Germans were already exhausted and demoralised by their lack of progress and severe losses. The mass of their army was now trapped in an ever-tighter Roman crescent, with the troops on the edges being methodically cut down and the ones in the middle packed tightly together and unable to move. Finally, after more relentless pressure from the Romans, the German line collapsed: as panic spread through their ranks, the Germans broke formation and ran for their lives. Many did not run fast enough: pursued all the way to the Rhine by Roman cavalry and infantry, many were cut down as they ran. Large numbers attempted to swim across the river, but many drowned, hit by Roman missiles or weighed down by their armour.
Ammianus reports that 6,000 Germans perished on the battlefield and in the pursuit on land. (Libanius gives a figure of 8,000). Thousands more drowned as they tried to get across the river. It is thus likely that about a third of the German force lost their lives. However, it appears that the majority escaped, including the eight reges alongside Chnodomar. The Romans lost just 243 men, including four tribuni (regimental commanders) of which two were commanders of cataphracti. Chnodomar himself and his retinue tried to escape by reaching some boats prepared for just such an emergency near the wrecked Roman fort of Concordia (Lauterbourg), some 40 km downstream from Strasbourg. But they were cornered by a Roman cavalry squadron in a wood on the bank of the Rhine and surrendered. Brought before Julian, whom he begged for mercy, Chnodomar was sent on to the court of Constantius at Milan. Not long afterwards, he died of disease in a camp for barbarian prisoners in Rome.
After the battle, Julian was acclaimed as Augustus (co-emperor) by his troops. But he vehemently refused the title, which could only legally be bestowed by the ruling Augustus, Constantius. Given the latter's murderous attitude against potential contenders, Julian's caution is understandable.
Aftermath
The immediate aftermath of the battle saw a vigorous "ethnic cleansing" campaign as all Alamanni who had settled in Alsace were rounded up and expelled from imperial territory.
The battle was the turning point in Julian's effort to restore the Rhine frontier. Until then, Julian was obliged to campaign largely inside Gaul, with the barbarian bands holding the initiative, playing cat-and-mouse with his forces and causing enormous economic damage to a vital region of the empire. Starting with the 358 campaigning season, Julian was able to take the war to the enemy, each year invading the lands beyond the Rhine, devastating them and terrorising the tribes into accepting tributary status. At the same time, he was able to make serious progress in repairing Rome's shattered line of forts. In Luttwakian terms, he was able to return to a traditional strategy of "forward defence" after being obliged by circumstances to engage in defence-in-depth for three years.
Still in 357, Julian followed up the battle by an incursion into Alamanni territory beyond the Rhine. After ravaging the lands far and wide, he set about rebuilding a fort in the Agri Decumates (Black Forest) originally built by Trajan in the early 2nd century. He then granted the anxious barbarians a 10-month truce.
In 358, Julian first turned his attention to the Frankish tribes, crossing the lower Rhine and forced the Salii and Chamavi tribes to surrender and become tributarii (tribute-payers). He then restored three important forts on the lower Meuse river. Finally, he switched his attention to the Alamanni, crossing the Rhine at Mainz and forcing the submission of the new paramount kings Hortarius and Surmarius.
In 359, Julian restored seven forts and town walls in the middle Rhine, including Bonna (Bonn) and Bingium (Bingen), obliging his new tributary Alamanni to provide the supplies and labour needed. He then crossed the Rhine, marched through the territory of the tributaries and devastated the lands of the other kings who had fought at Strasbourg, including Westralp. All were forced to submit and return the thousands of Roman civilians they had abducted and enslaved during the years of easy plunder.
By 360, Gaul was sufficiently secure to permit Julian to despatch reinforcements of ca. 3,000 men under magister armorum Lupicinus to Britain, which had suffered a serious land and sea invasion by the Picts of Scotland and the Scotti of Ireland. But at the same time, Julian received a demand from Constantius, who was unaware of the British expedition, that he send 4 auxilia palatina regiments plus select squadrons of cavalry (ca. 2,500 men) under Lupicinus to the East as reinforcements for the war against the Persians. This triggered a near-mutiny by Julian's soldiers, who again proclaimed him Augustus. He again refused, but this time, the troops insisted, making it clear they would mutiny if he refused and march against Constantius with or without him. Alarmed, but also secretly pleased, Julian accepted the title and wrote an apologetic letter to Constantius explaining why he had felt it necessary to bow to his soldiers' wishes and requesting his ratification. But this was refused by Constantius, who replied demanding that Julian revert to Caesar status. Julian ignored the order, but to prove his good faith and also to keep his near-mutinous troops occupied, he crossed the Rhine and attacked the Attuarii tribe of the Frankish confederation. The following year, however, Julian decided to confront Constantius and the two emperors marched against each other to settle the issue. But the empire was spared another civil war by the senior emperor's sudden death in Asia Minor (361).
As sole emperor (361-3), Julian succumbed, as many Roman leaders before him (e.g. Crassus, Trajan, Septimius Severus) to "Alexander the Great syndrome": the desire to emulate the Macedonian general and conquer the Persian empire. He invaded Mesopotamia at the head of an enormous army of 65,000. But the campaign was a disaster: Julian lost his own life and his army was forced to retreat with huge losses. Although most of these would have been from the eastern comitatus and from the emperor's own escort army, the comitatus of Illyricum and Gaul would undoubtedly have been stripped of troops to fill the gaps. The result was that in 366 Gaul was again overrun by Alamanni hordes and Julian's painstaking work of restoration undone. This forced Julian's successor, Valentinian I, to spend years carrying out a virtual replay of Julian's Gallic campaign.
Roman order of battle
The composition of Julian's army at Strasbourg can only be partially reconstructed. Ammianus gives the names of only five regiments in his account of the battle itself. But at other points of Ammianus' narrative of Julian's campaigns in Gaul, and also in Zosimus' history, there are mentions of other regiments in his comitatus, which were very likely at Strasbourg also.
A comitatus at this time probably contained only three types of regiment, all of them of the top, palatini, grade: cavalry vexillationes and infantry legiones and auxilia. There is much uncertainty about the size of late Roman army units. The official strength of vexillationes and legiones seems to have been 800 and 1,200 respectively. But actual strengths recorded were 400 and 800 respectively. A midpoint between these figures is assumed here of 500 for vexillationes and 1,000 for legiones palatinae. The strength of the auxilia palatina regiments is disputed. They may have been as large as legions, or only half the size. Half the size is more likely, as it accords best with the available evidence. Also, if an auxilium was the same size as a legion, there would seem little purpose in the distinction between the two types of unit.
The sources give the following units for Julian's comitatus:
REGIMENTS IN JULIAN'S COMITATUS, 355-60
! Legiones | Auxilia | XXX | Vexillationes | Ioviani
Herculiani
Primani*
Moesiaci (1)
Moesiaci (2) | Batavi*
Reges*
Cornuti*
Brachiati*
Celtae
Heruli
Petulantes
| | Normal
Equites Gentiles
Equites scutarii*
Heavy
Equites cataphractarii (1)*
Equites cataphractarii (2)*
Light
Equites Dalmatae
Equites sagittarii* | | Total (inf) 5,000 | Total (inf) 3,500 | | Total (cav) 3,000 |
NOTE: Asterisk indicates unit specified by Ammianus at Strasbourg
The Ioviani and Herculiani legions and equites Dalmatae are not mentioned by the sources as under Julian, but as part of the Gaul comitatus of usurper Magnentius. They are likely to have been inherited by Julian. If all these units were present at Strasbourg, the infantry total is 1,500 short, or 3,500 if Severus commanded an extra 2,000 men. Probably the names of a number of auxilia regiments (and possibly a legion) are missing in our sources. If so, at least one of these units is likely to be a sagittarii (archer) unit, as a comitatus would be incomplete without archer capacity. Overall, the most likely scenario is that Julian's force at Strasbourg consisted of 5-6 legiones and 10-14 auxilia of infantry and 6 vexillationes of cavalry.
As regards cavalry, Ammianus mentions only cataphracti in his account of the battle. But it is virtually certain that they were only part of his force. In the late army as a whole, only 15% of cavalry regiments were heavily armoured cataphracti. These were suitable for the shock charge. Two tribuni (regimental commanders) of cataphracts were reported killed at Strasbourg. There were thus at least two vexillationes of cataphracts (1,000 horse) engaged. Elsewhere in Ammianus and Zosimus it is stated that Julian had a regiment of Gentiles and a regiment of scutarii under his command. Both these were normal (semi-armoured) units that represented the majority (61%) of the late army's cavalry and were best suited to mêlée combat. There is also mention of light (unarmoured) units of equites Dalmatae (javelineers) and equites sagittarii (mounted archers). Light cavalry was used for harassment and pursuit. The likeliest scenario is that all these were present at Strasbourg, with 2 vexillationes each of heavy, normal and light cavalry engaged. It is thus likely that cataphracts were about a third of Julian's cavalry at Strasbourg, an unusually high proportion. In addition, Julian had his personal escort of 200 picked cavalry.These were probably a detachment from one of Constantius' scholae (elite cavalry squadrons, believed 500-strong, that served as the imperial horse guard).
As regards the line of battle, we are given a little information by Ammianus. He reports that the right flanks of each line, front and reserve, were held by 2 auxilia regiments and the centre of the reserve line was held by the Primani legion. A possible order of battle that fits the available evidence is shown in the diagram of the battle.
Alamanni forces
At Strasbourg, there were 8 reges (kings): Chnodomar and his nephew Serapio; Westralp, Urius, Ursicinus, Hortarius, Suomarius; and the treaty-breaker Wadomar (his colleague Gundomad had been slain and it is unclear whether he had been replaced, or whether Wadomar commanded the forces of both kingdoms). Each would probably have had two pagi under him making a total of 18 pagi. The Alamanni forces would likely have been divided into pagus contingents.
Citations
Ancient
Modern
- Drinkwater, J. F. (2007) The Alamanni and Rome (213-496)
- Elton, Hugh (1996), Roman Warfare 350-425
- Goldsworthy, Adrian (2000), Roman Warfare
- Jones, A. H. M. (1964), Later Roman Empire
- Raddatz, K. (1967), Die Bewaffnung der Germanen in der jüngeren römischen Kaiserzeit [German]
- Speidel, M. (2004), Ancient Germanic warriors, warrior styles from Trajan's column to Icelandic sagas
See also
Late Roman army
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