Rome’s civil wars split the state into factions, and the army with it. Since there were no ethnic, ideological or social differences between the rival sides, it was inevitable— even more than in any other civil war—that the organisation, tactical doctrine and equipment of their armies was virtually identical. The main strength of the Roman army lay in the legions, units with a paper strength of about 5,000. In theory the legions were recruited only from Roman citizens, but during the civil wars many non-citizens were enlisted to bolster numbers. In his Commentaries, Caesar frequently emphasised the heterogeneous nature of the enemy armies, but he had himself formed an entire legion, Legio V Alaudae, from Gauls, only later giving them the franchise as a reward for distinguished service. Given the dominance of the Roman military system, some allied kings had remodelled their armies after the Roman style. King Juba of Numidia included four legions in his large army, while Deiotarus of Galatia formed two which would later be amalgamated and formed into Legio XXII Deiotariana as a fully fledged part of the Roman army.
In this period a legion consisted entirely of heavy infantry. It had no permanent commander, but the practice had evolved of appointing an officer, usually one of the general’s representatives, or legates, to fulfil this role. Much of the unit’s administration was overseen by the six military tribunes, probably assisted by a small staff. These were largely equestrians (the class immediately below the Senate and possessing similar property) and at that time many were career soldiers of considerable experience. The basic tactical unit of the legion was the cohort of some 480 men. There were ten of these in each legion, and the cohort in turn was subdivided into six centuries of 80. The century was led by a centurion, supported by an optio (second-in-command), signifer (standard-bearer), and tesserarius (guard commander). Centurion represented a grade of officer rather than a specific rank and these men differed greatly in seniority. On several occasions Caesar mentions rewarding brave centurions by promoting them to a higher grade, often in a newly formed legion that would benefit from having experienced officers. One of the six centurions probably acted as commander of the cohort, either the man with longest service or the centurion of the senior century, the pilus prior.
This scene from the lst-century monument to Domitius Ahenobarbus shows legionaries wearing a uniform which would not have been out of place during the Civil War. They wear mail armour Montefortino-type helmets and carry long oval shields. (AKG Berlin)
All legionaries were equipped with the same basic defensive gear, consisting of a bronze helmet (most often of Montefortino or Coolus patterns), cuirass (usually mail but sometimes of scale), and a large semi-cylindrical bodyshield constructed from three layers of plywood to give it both flexibility and strength. The latter seem most often to have been oval in shape, but it is possible that the transition to a more rectangular shape was already underway. Such shields were heavy— reconstructed examples weighing in at 22lbs— but offered good protection. They could also be used offensively, the soldier punching forward with all his body weight behind the shield’s bronze boss. We are told that one of Caesar’s soldiers, in spite of having his right hand chopped off almost as soon as he had boarded a warship, was able to clear the deck of enemies by knocking them down with his shield during the fighting off Massila. A soldier’s other offensive equipment consisted of a short sword, the famed gladius, sometimes a dagger, and a heavy throwing javelin known as the pilum. The pilum consisted of a wooden haft about 4 feet long, topped by a narrow iron shank 2 feet in length and ending in a pyramid-shaped point. When thrown, all of its great weight was concentrated behind this small tip, giving it formidable penetrative power. It was designed so that once it punched through an enemy’s shield, the slim iron shank would slide easily through the hole made by the point and had the reach to wound the man behind. Soldiers may have carried two pila on campaign, but only one on the day of battle itself. The doctrine of the period was to deliver a massed volley at very short range—some 15 yards or so—and follow this up with a charge, sword in hand.
Roman legionaries were not simply soldiers, for many were trained as engineers or artillerymen. Such men remained with their cohorts until required, and were then formed in temporary units to complete a task. The Civil War would be marked by many remarkable feats of engineering.
In battle a legion most often formed in three lines, four cohorts in the first line and three each in the second and third. Intervals were maintained between each unit and the cohorts from the next line stationed to cover these gaps, creating something resembling a checkerboard formation. However, since all cohorts were armed uniformly, the legion was perfectly capable of fighting effectively in other formations, and we also hear of armies in four or two lines, although a single line was considered too brittle to be employed save in dire need. The legion was a very flexible force. Its structure and size made it an important subunit within the battle line, but one or several cohorts could as easily be detached for smaller operations. As with all armies throughout history, theoretical unit sizes were rarely reflected in the field. At Pharsalus the cohorts of Pompey’s legions averaged around 400 men apiece, while Caesar’s force was little more than half that size. Campaign attrition reduced one of Caesar’s legions to less than 1,000 men during the Egyptian campaign.
The Coolus-type helmet (the name is modern) was one of the commonest patterns worn by legionaries in the Late Republic. Made from copper alloy and following Gallic design, it offered protection to the top of the head whilst cheekpieces protected the face. Many examples from this period are of poor quality the bowl spun rather than beaten into shape, probably because of the need to equip mass armies. (British Museum)
The legions were the mainstay of any army, especially decisive in pitched battles, but both sides supplemented their numbers with allied soldiers or auxiliaries, fighting in their own traditional style. Such troops were especially useful in providing cavalry and light infantry. In most cases they were locally recruited and led by their own native chieftains. At first Caesar’s auxiliaries came primarily from the Gallic and German tribes, and Pompey’s from his provinces in Spain and his many clients in the east, but as the war progressed, troops were recruited wherever possible and the pattern became more complex.
By the end of the Gallic campaigns, Caesar commanded ten legions (numbered V to XIV). Two more, XV and I, the latter on loan from Pompey’s Spanish armies, had been withdrawn earlier in 50 to be sent against the Parthians. The majority of these troops were seasoned veterans, utterly devoted to Caesar and confident in their own and their commander’s ability. In support were bands of excellent Gallic and German cavalry. To match against this Pompey had seven legions garrisoning his Spanish provinces, although these had little actual combat experience. There were also the I and the XV which had not yet left for the east and were still in Italy but as both had recently served under Caesar their loyalty appeared questionable. However, he boasted that he had only to stamp his foot in Italy for more legions to appear, and was also sure of the loyalty of the eastern provinces which he had reorganised just over a decade before. In the long term, Pompey could probably claim greater resources than Caesar, but it would take time to mobilise these into field armies.
In 49 Pompey was almost 58, but remained an extremely fit and active man, and others marvelled at the energy he showed in joining the training exercises of his soldiers. His military record was extremely good, even if he had made something of a habit of arriving in the last stages of a conflict to claim the credit largely won by someone else. He was certainly a brilliant organiser, as the campaign against the pirates, as well as, more recently, his supervision of Rome’s corn supply, had shown. In his youth he had been a bold commander, on several occasions leading charges in person, but his aggression, in a properly Roman way, had always been based on sound preparation. However, although he was only six years older than Caesar, Pompey had spent the last decade in Rome and had not served on campaign since 62. His performance during the Civil War would suggest that he was past his best as a general. He was not helped by the presence of so many distinguished senators in his camp. Unlike Caesar, whose followers were undistinguished and whose authority was unchallenged, Pompey was always under pressure to alter his plans. Most of the senators who flocked to his cause had more prestige than ability, and on more than a few occasions proved a positive hindrance. The ablest of his subordinates, Titus Atius Labienus, had served with Caesar throughout the Gallic campaigns. It is probable that he had a prior connection with Pompey, for he defected from Caesar’s camp at the beginning of the war. On hearing of this, the latter ordered his baggage to be sent on after him.
The Kasr el-Harit shield. This shield found in Egypt just before the Second World War was originally identified as Gallic but is most probably Roman. Made of three layers of plywood, it is remarkably similar to the Roman shield described by the Greek historian Polybius in the late 2nd century BC. (Nick Sekunda)
Caesar failed to attract any distinguished supporters from the senior members of the Senate. Now in his early 50s, he was still very much at the peak of his ability, and was fresh from a decade of successful fighting in Gaul. His strategy during the Civil War, as in Gaul, was based on rapid offensives, sometimes in the face of great odds. Though often criticised for recklessness by modern commentators, it is important to emphasise that such boldness was characteristically Roman, and should not conceal that much preparation underlay these enterprises. Although subject to occasional epileptic fits, he was in other respects an extremely healthy and active man, capable of massive effort and rapid long-distance travel. Caesar promoted and lavishly rewarded any soldiers who distinguished themselves, but even more than this it was his remarkable charisma that ensured that his soldiers were devoted to him. Throughout the war, desertions from the Pompeian forces were common, but all of our sources claim that there were no defections in the other direction. Fighting a war to protect his own honour and status, Caesar’s objective was clear and obvious, giving the Caesarian war effort a unity of purpose not displayed by the other side. Yet it also meant that it was much easier for him to lose. If Caesar were killed, or his army defeated so heavily that he was discredited, then the war would effectively have been over. Only the Pompeians could suffer defeat after defeat and still prolong the struggle.
It is hard now to say whether Pompey or Caesar was the better general. The vast bulk of our evidence comes, directly or indirectly, from Caesar’s version of events. His Commentaries obviously present his own actions in a favourable light, while dismissing those of the enemy. However, they also provide evidence that allows the wisdom of some of Caesar’s decisions to be questioned. Yet, for the Romans the answer was obvious, for the most important attribute of a great general was that he won his wars. Caesar defeated Pompey, and in the end there was no more to be said.
This frieze from the headquarters building of the legionary fortress at Mainz in Germany dates to over a century after the Civil War; but gives a good idea of the classic fighting stance of the legionary—crouching slightly to gain the maximum protection from his shield, with his left leg advanced and sword thrust underarm. (AKG Berlin/Erich Lessing)