Julius Caesar and the Art of Hybrid War

Bijan Omrani

A friend in the world of defence think-tanks contacted me the other day to ask for a Classical perspective on his work. He was thinking about the ideas of ‘hybrid war’ or ‘grey-zone war’ – new buzz-words which signify the idea of countries conducting warfare somehow ‘under the threshold of full combat’. Many defence analysts view Russia as being partial to this sort of approach, particularly at present with Ukraine. It might include subterfuge, deception, undermining alliances, special forces activity, psychological operations, political subversion, as well as cyber, economic, and information warfare.

But, asked my friend, isn’t all this chatter in the defence world just a fad, and nothing new at all? “For example, my recollection of reading Caesar’s Gallic War at school is that, while Julius Caesar was all for set-piece battles, he also engaged in this stuff too, didn’t he?”

My friend’s question got me thinking. One could probably identify a long list of instances where Caesar resorted to such tactics (except, perhaps, cyber warfare).[1] Yet, in one important respect, Caesar was, in my view, particularly adept. This was in fighting information wars, and in particular, finding pretexts to justify his wars of European conquest. This article will offer one example: the military action which was to spark his conquest of Gaul, by which he was to change the face of Europe for good.

Julius Caesar dictating his commentaries, Pelagio Palagi, 1813 (Palazzo del Quirinale, Rome, Italy).

When Caesar (100–44 BC) ended his year as consul at the beginning of 58 BC, he was in desperate need of money. His rise to the highest office had been financed by Marcus Licinius Crassus, one of the richest men in Rome. Caesar had used Crassus’ money to pay for extravagant shows, as well as bribery, to ensure his success in the elections. This money would have to be repaid. Many in Rome were also hostile to Caesar, seeing him as a threat to the Republican order. Some were hoping to prosecute him for his actions as a consul, on the grounds that he had passed laws unconstitutionally.

However, Caesar had been given the five-year proconsular administration of three provinces after his consular term: Illyricum, on the Adriatic coast; Cisalpine Gaul, the northern part of Italy; and Transalpine Gaul, an area of Gaul mostly along the southern coast of France, which Rome had annexed by around 120 BC. Like other former consuls, Caesar hoped to make money in provincial administration. The chance to fight battles and capture plunder in these circumstances would greatly increase the funds he could amass, but also enhance his political stature, protecting him against his enemies at Rome. Yet, he couldn’t march the troops out of his provinces or take them into battle without good cause.

Early in 58 BC, soon after his proconsulship began, Caesar found his opportunity. A large tribe, the Helvetii, who lived in the region of modern-day Switzerland outside the area of Roman control, wanted to migrate westwards into non-Roman Gaul. The easiest route would take them across a small part of the Roman province of Transalpine Gaul, before they again returned to the area beyond Roman jurisdiction. Caesar received news that they were intending to cross the Rhône by a bridge at the Roman frontier town of Geneva, and then pass on their way out of the Roman sphere.

Modern bridges over the Rhône in Geneva, Switzerland.

Caesar’s reaction was immediate. His snap decision was that any movement of the Helvetii would pose an existential threat to the Roman provinces. He was just outside Rome, but rushed to Geneva, and ordered the bridge to be broken down. The Helvetii then sent ambassadors asking Caesar for permission to cross the river. Caesar delayed giving an answer for two weeks, until mid-April. Caesar only had one legion on call in the area, and he used the time to start raising further troops. However, he used the troops then at his disposal to fortify a 19-mile stretch of the south bank of the Rhône, to prevent the Helvetii from crossing by boat. Those who later attempted to do so were easily repulsed.

In mid-April, Caesar finally told the Helvetii that they would not be allowed to cross Roman territory. They therefore started to plan to take the only other available route – a narrow pass through the Dura mountains on the north bank of the Rhône. This route was so narrow and difficult, as Caesar himself said, “that carts could scarcely be drawn in single file along it.” The Helvetii made agreements for safe passage with the Gallic tribes through whose territory they would travel, and took the slow and gruelling journey through the pass, watched over by Caesar’s troops on the south bank of the Rhône.

Map of the route of the Helvetii from Geneva to the Pas de L’Ecluse, showing Roman fortifications (based on the excavations of Colonel Eugene Stoffel in the 1860s).

They did not get very far. Soon after they debouched into open territory, they were met by Caesar and his legions, who had marched beyond the bounds of the Roman province to hunt them down. Caesar first attacked a group of the Helvetii unawares as they were attempting to cross the River Saône. According to Caesar, this group was a quarter of the whole number. It would have consisted both of fighting men, as well as women and children. They were heavily laden with baggage for their journey. A large number were killed, and many were scattered.

The remainder sent an ambassador to Caesar to seek peace, and to agree that they would settle wherever Caesar should order them. However, records Caesar, when they refused to offer hostages for good conduct, he rebuffed their approach. Caesar met the remainder of the Helvetii at the Battle of Bibracte (which probably took place near Toulon-sur-Arroux south of Dijon). Unsurprisingly, Caesar’s forces got the upper hand. According to his reckoning, around two-thirds of the migrants were killed or enslaved. The Romans captured their baggage, and ordered the remainder to return to the lands from which they had travelled.

Caesar’s account of his visit to Geneva quoted verbatim in a modern inscription by a river crossing in the city. The text, quoted from Bellum Gallicum 1.6.3, can be read in Latin and English here.

Caesar’s account of the affair is given at the beginning of Book One of the Gallic Wars. This may well have been circulated in Rome to report on his achievements in the field. His prose is so simple, unadorned, and down-to-earth, that it sweeps along the reader with a sense of inevitability. It attempts to give the impression that Caesar was a highly practical commander dealing with a dangerous situation, and that he had no alternative but to act in the way that he did. Yet, a close interrogation of Caesar’s account brings this all into doubt.

The first matter is the question of whether Caesar’s march out of the province and two battles with the Helvetii were at all necessary in military terms, if the simple objective had been to prevent the Helvetii from leaving their original homeland around Geneva. The answer lies in the geography of the route. To leave Geneva, they had to follow the narrow pass on the north bank of the Rhône. One can follow the route today, from Geneva to the dizzying modern fortress on the Pas de l’Ecluse. Doing so, it is immediately apparent that the path could have been blocked with little effort, making it completely impassable for the Helvetii. Caesar fortified the whole of the south bank for 19 miles with the forces at his disposal. It would have been no difficult task to cross the river and cut off the narrow path, thus bottling up the migrants indefinitely, without having to resort to combat.

The Fort de L’Ecluse, which guards the narrow pass through the Jura Mountains above the Rhône, close to the modern Swiss-French border.

Yet, Caesar chose not to do so. However, his account moves so swiftly, and relies on our own lack of close acquaintance with the terrain, that we do not think to ask why he did not stop them. Caesar instead allowed the Helvetii to make their way through the pass, with the result that he could fight set-piece battles against them on favourable territory and win glory by killing large numbers, enslaving many, and taking spoils, just as he needed.

There is also the matter of Caesar’s presentation of the Helvetii. Again, his brisk overview of the matter seems at first sight cogent and level-headed. Their current homeland, he claimed, hemmed in by various rivers and mountains, was too small for their aspirations. They were a people that longed for war and domination. Indeed, they played an integral part in the destruction of a Roman force half a century beforehand. This was when they assisted another column of northern migrants, the Cimbri and Teutones, who were bearing down towards the Roman province, to overcome a Roman detachment at Orange near the Rhône. Their leader, Orgetorix, wanted to become master of Gaul. He was conspiring with leading men of other tribes to achieve this end.

A Celtic coin minted by the Helvetii, probably in the late 60s BC; Orgetorix is named as Orciitrix.

He was also instrumental in persuading the Helvetii that they could take charge of Gaul if they simply migrated from their current homeland. Although his conspiracy with other tribes had later been discovered, and he had committed suicide as a result, the Helvetii still followed his three-year plan to prepare themselves for a wholesale migration. As they moved past the Jura mountains, they were also foraging, attacking, and plundering the Gallic tribes through whose territories they were moving, despite their agreements for safe passage. Some of these tribes that had been attacked were allies of Rome. If the Helvetii were to settle, as he had heard was their intention, near the Roman provincial town of Toulouse in a grain-rich area, it would be a recipe for terrible instability and danger for the whole Roman province. For all of this, argues Caesar, it was necessary for him to act.

Track by the Rhône beyond the village of Collognes that the Helvetii would have followed to the Pas de L’Ecluse.

However, in his description, one notices Caesar returning repeatedly to one point in his presentation: the connection between the Helvetii and the earlier migration of the Cimbri and Teutones. This event occurred in the final decade of the 2nd century BC. It caused huge panic in Rome, partly because the large column of migrants attempted to enter Italy itself, but also because it evoked Rome’s deep-seated fear of a Gallic invasion. The Gauls had been the only people previously to capture and burn Rome in 390 BC. The event had a profound impact on the development of the city, and the scars of it were still visible even in Caesar’s day.

The Gallic sack of Rome in 390 left traumatic memories in the city, and an abiding fear of another Gallic attack (detail from Paul Lehugeur’s engraving of the Gallic chieftain Brennus in his Histoire de France en cent tableaux (A. Lahure, Paris, 1886).

Caesar also evokes the figure of Marius (c. 157–86 BC) several times, the populist general and politician who had won huge acclaim during the crisis of the Cimbri and Teutones by restoring order to the demoralised Roman army and destroying the migrant columns of the Cimbri and Teutones as they attempted to enter Italy. Following his success, Marius became the de facto leading power in Rome. Marius was also Caesar’s uncle.

Read with this in mind, Caesar’s presentation of the Helvetii begins to look suspicious. Caesar is insistently trying to place them in the mould of the Cimbri and Teutones. Rome, he suggests, had to fear the Helvetii, since it was a situation as grave as the earlier crisis. He evokes the deep-seated fear of Gallic invasion. But he also implies that he himself is the new Marius, a military genius who can save Rome, and who is therefore also worthy of the highest power.

If the real purpose of Caesar’s narrative is to generate spin to justify an offensive campaign and cast himself as the successor to Marius, it prompts us to interrogate his account of the facts even more closely. When one does so, further doubts arise. It should be borne in mind that, aside from a couple of glancing references in letters of Cicero (106–43 BC), it is only in Caesar that any detail is found on the issue of the Helvetii.

Silver denarius of 48/47 BC celebrating Caesar’s victory over the Celts: the bearded figure on the reverse may be Vercingetorix, chieftain of the Arverni, defeated and taken captive at the Battle of Alesia in 52.

This being so, and with Caesar’s own sources for the internal dealings of the tribes being unknown, one has to ask whether it is really credible that the Helvetii set off with the intention of taking sovereignty over Gaul. Is it not more likely that this is Caesar’s projection of his own desires onto an enemy? If the Helvetii were angered at the idea of a conspiracy, why did they follow the plans laid down by its instigator, Orgetorix, after his death when they had been on the verge of executing him? Is it likely that the Helvetii could have gained the cooperation of other tribes for their movement through their territories if those tribes genuinely saw the Helvetii as a threat, and could have bottled them up at the Pas de l’Ecluse, even if the Romans had chosen not to?

Is Caesar’s account of the belligerence of the column of Helvetii migrants towards other Gallic tribes credible, when the column was large, slow moving, encumbered with three months’ worth of supplies and followed by women and children? It seems more vulnerable to attack than a source of attack. Moreover, if the migrants were such a danger, why were around a tenth of them (the Boii, “known to be of remarkable courage” in the words of Caesar) settled with the offer of farmland amongst the allied Roman tribe of the Aedui, at the Aedui’s own request and with Caesar’s own consent?

Perhaps the migration of the Helvetii would have caused disturbances beyond the Roman frontiers, and even some difficulties to Gallic tribes allied to the Romans. Yet a close reading of the evidence instead suggests that Caesar was exaggerating the case for armed intervention for his own benefit, and even manipulating the course of events on the ground to allow this to take place.

The opening of Caesar’s Bellum Gallicum in a well-thumbed 11th-century manuscript (British Library 10084, written in France), which can be read freely here. The initial ‘G‘ of Gallia is missing: the specialist artist who was supposed to provide an enlarged and illuminated initial never did his work.

The conflict with the Helvetii was not the only time that Caesar came up with a doubtful pretext for a new action that would allow him further to pursue the conquest of Gaul. He used a similar ruse to his attack on the Helvetii for his confrontation with the Germanic leader, Ariovistus, straight after the Helvetii campaign. He spuriously claimed that his brutal obliteration of the seafaring Veneti tribe on the western coast was provoked by their attack on legates acting in a diplomatic capacity. He also claimed that his need to invade Britain (for which he was accorded the honour of 20 days of public thanksgiving in Rome) was necessitated by fighters using the island as a refuge from which to attack the Romans on the Gallic mainland – a point for which he adduces little convincing evidence.

Caesar was undoubtedly a brilliant military commander in the field. Yet it was also his capacity to manipulate a situation – his mastery of hybrid war, if you will – that allowed him to gain a greater magnitude of success. Casting our eyes to the frontiers of eastern Europe in the present day, it may be that those who can find pretexts for action as deftly as Caesar, or else undermine the pretexts of the opposing side, are those to whom the initiative in any conflict is likely to belong.

Bijan Omrani is an Honorary Associate Research Fellow at the University of Exeter. His books include Afghanistan: A Companion and Guide, and Caesar’s Footprints: Journeys to Roman Gaul. He has written for Antigone on the Greeks, Afghanistan and Buddha here, and on Ausonius here.

Further Reading

Caesar’s account of his attack on the Helvetii is to be found in the first book of the Gallic Wars, which can be read in Latin and English via the Perseus Project here. There is a wealth of modern material on Caesar and his conquests. Adrian Goldsworthy’s Caesar (Phoenix, London, 2006) is the most useful and comprehensive, and which also offers a different view to this article on the action against the Helvetii. Michael M. Sage, Roman Conquests: Gaul (Pen & Sword, Barnsley, 2011) is a useful recent book with a particular focus on the military aspects of the conquest. Andrew Riggsby’s Caesar in Gaul and Rome: War in Words (Univ. of Texas Press, Austin, TX, 2006) looks at Caesar’s literary construction of the Gallic Wars. Josiah Osgood’s “The pen and sword: writing and conquest in Caesar’s Gaul,” Classical Antiquity 28 (2009) 28–58 also deals with this area. I myself discuss Caesar and the Helvetii in Chapter 2 of Caesar’s Footprints: Journeys to Roman Gaul (Head of Zeus, London, 2017).


1 That said, Caesar’s adoption of encrypted messaging was significant, as we have seen elsewhere on Antigone.