Focus on the Literature of War: Julius Caesar’s Gallic War

The Hellenistic era (323-31 BCE) was a dynamic era of military history, an era which inspired and influenced Hellenistic Greek and later Roman historians, whose chronicles of these centuries have shaped our modern understanding of Hellenistic and Roman warfare. Most of the important chroniclers of Philip II and Alexander the Great’s conquests, as well as those of the Hellenistic Successor States and the rise of Rome as a Mediterranean power, lived hundreds of years after these events during the time of the Late Republic or Early Roman Empire. The two most important biographers of Alexander, Diodorus Siculus (first century BCE), and Arrian of Nicomedia (c.86-160 CE) compiled histories of the early Hellenistic era using sources written closer to the events but no longer extant. Livy (59 BCE-17 CE), whose treatment of the history of Rome (From the Founding of the City or Ab Urbe Condita) from the Regal era to the reign of Caesar Augustus, is another prime example of a classical historian relying on earlier scholarship to compile his history. Other historians wrote histories closer to their own age. Polybius (200-118 BCE), a Greek historian who chronicled the Punic and Macedonian conflicts, as well as the Romano-Syrian wars. In fact, his description of the changes to the organization of the Roman legion in the Middle Republic (264-133 BCE)  have taken on his name, described as the “Polybian Legion” due to his careful description of its organization and application in war. Other classical era historians like Plutarch (46-120 CE), Tacitus (c.56-118 CE), and Arrian of Nicomedia (c.86-160 CE) compiled histories using sources written closer to the events but no longer extant.

RIGHT: The Chiaramonti Caesar Bust. This sculpture is a posthumous portrait in marble dating to after his assassination in 44 BCE. Museo Pio-Clementino, Vatican Museums. Source: Wikimedia.

Of special note are Tacitus’ Germania, perhaps the greatest classical era explanation of the Germanic peoples, and his Histories and Annals, describing the Early Roman Empire, and Arrian’s military history-centric history of Alexander the Great. Written during the reign of Emperor Hadrian (r.117-138 CE), Arrian’s Campaigns of Alexander (referred to in Latin as the Anabasis Alexandri) is the most accurate and complete biography of the young Macedonian king’s conquests, providing excellent information on Alexander’s campaigns, including details of Macedonian (and rival) generalship, military organization, weapon descriptions, and operations.  Arrian was a civil servant, military commander and historian who modeled his treatment of Alexander after writings of Xenophon. Later in the Roman imperial era, another civil servant with military service, Ammianus Marcellinus (c.330-395 CE) chronicled the era of the “Five Good Emperors” (96-180 CE) to the decisive Roman defeat at Adrianople at the hands of the Visigoths in 378 CE, while also providing great insights into Roman court intrigue and Roman campaigns against the Parthians and Sassanian Persian in the East. Like the histories of Greek historians Herodotus and Thucydides, these Roman works are presented as general histories and not military manuals, although very specific information on military matters is often present. And importantly, many of these histories were available to later Roman and Byzantine military practitioners and were studied for military applications in later eras.  There is, however, one chronicle dating to the middle of the first century BCE which has a special place in Roman military history, Julius Caesar’s autobiographical account of his Gallic campaigns. 

Julius Caesar’s Commentaries on the Gallic War, 51 BCE

Republican Rome (509-31 BCE) was the heir to many Hellenic and later Hellenistic military organizations, technologies and tactics, however, over the half millennium history of the republic, Rome developed unique military institutions on the way to dominating the Mediterranean world. Roman Republican history is usually split into three eras: the Early Republic (509-264 BCE), the Middle Republic (264-133 BCE), and the Late Republic (133 -31 BCE). In the Early Republic Rome defeats the Etruscans and tribal mountain enemies and consolidates the Italian Peninsula as part of its expanding territory. In the Middle Republic Rome expands into a naval power and defeats Carthage and three Punic wars, while simultaneously fighting in the East against the Hellenistic Macedonian and Syrian kingdoms. In the Late Republic, Rome focuses a consolidating newly conquered areas, while expanding its territories in Anatolia, the Levant, in North Africa and finally across the Alps into Gaul. Although we have some historical accounts of the campaigns of great Roman (Scipio Africanus, Julius Caesar, Octavian and Mark Antony) and occasionally enemy commanders (Hannibal Barca) during this time span, there are no dedicated Roman military manuals that have survived intact from this era.

LEFT: A line drawing of Caesar's Rhine Bridge by Thomas Rice Holmes (1855-1933) from C. Iuli Caesaris Commentarii rerum in Gallia gestarum VII ; A. Hirti commentarius VIII. Edited by Thomas Rice Holmes. 

The Roman military experienced a major reorganization in the late second century BCE when the general and serial consul Gaius Marius (157-86 BCE) instituted his Marian Reforms, creating the foundations of a full-time professional army and navy, a military which would see service against Rome’s enemies across the Mediterranean basin, as well as against one another in a series of Roman civil wars. The creation of the First Triumvirate in 59 BCE brough some temporary political stability and allowed Gnaeus Pompeius (Pompey, 106-48 BCE), Marcus Licinius Crassus (c.115-53 BCE), and Gaius Julius Caesar (100-44 BCE) to dominate the political scene in Rome and achieve their basic aims: Pompey received lands for his veterans and a command in Spain, Crassus was given a command in Syria, and Caesar was granted a special military command in Gaul. Of the three, Caesar made the most of his military appointment to gain both wealth and military reputation, recording his exploits in Gaul in his own Commentarii de Bello Gallico or Commentaries on the Gallic War (usually shortened into Gallic War, probably written in the winter of 52 into 51 BCE).

Julius Caesar’s Gallic War provides important information into the Roman art of war in the mid-first century BCE. Caesar’s campaign took place between 58 and 52 BCE throughout the region of Gaul (with two additional cross-channel raids against Britain in 55 and 54 BCE). The Celts did attempt to unite and defend themselves against Caesar under Vercingetorix, this alliance came too late and Celtic king was captured in 52 BCE at the siege and battle of Alesia. Six years later Vercingetorix took part in Caesar’s triumph at the end of the Civil War against Pompey and was later executed by strangulation on his order. Although characterized as a preemptive or defensive campaign, Caesar’s campaign was in fact a war of pacification and annihilation which brought the region of Gaul into Rome’s control and set the Rhine River as Rome’s northern border for centuries. And though written for mostly political purposes at the time and famously in third person (illeism), his Gallic War should be seen as an example of military philosophy composed by the practitioner himself, providing important insights into a Late Republican-era Roman army on campaign.

In Book One of his Gallic War, “The Campaign of 58 BCE,” Caesar opens by explaining the changing strategic situation in Gaul and the threat presented by the Celtic Helvetii tribe, a threat requiring direct Roman military intervention. Caesar discusses the defeat of the Helvetii in June of that year, presenting himself as a commander who shares the burden of combat with his men: “Caesar first had his own horse and out of sight, then all of the others, too: he wished to make the danger equal for all and take away any hope of flight.  Then, having urged men on, he joined battle.”

RIGHT: The fortifications built by Caesar in Alesia. The inset map shows a cross locating the battle site of Alesia in modern France, what was the region of Gaul during the time of Caesar. The circle shows the weakness in the north-western section of the fortifications.

Book Two, ”The Campaign of 57 BCE,” begins with Caesar battling the Belgae in northern Gaul while his lieutenant Publius Crassus battles the maritime tribes along the North Sea coast of Gaul. These two operations significantly extend the area of Rome's influence. Book Three: ”The Campaign of 56 BCE” opens with Caesar sending Servius Galba to open a route through the Alps and Caesar consolidating his newly conquered territories in northwestern Gaul, putting down rebellions, while other parts of his Roman army defeat new tribes, expanding Roman power. Here, Caesar describes combined naval and land tactics in support of these campaigns, giving important insight into these joint-force operations.

Book Four, ”The Campaign of 55 BCE,” concerns Caesar’s campaigns along the Rhine River and across the English Channel against the Celtic Britons harboring refugees from his Gallic campaign. Caesar orders the construction of a temporary bridge to span the fast-moving Rhine River in a strategy designed to intimidate rebel barbarians who had fled across the river. He provides extraordinary detail in the construction of the bridge, giving modern scholars a vivid illustration of Roman military engineering:

“This was the method applied to building the bridge: he took pairs of posts a foot and a half thick, cut to a length greater than the river’s depth, and with short points at the lower ends, and joined each pair together with a two foot space between them. Using specialized machinery, he set them in the river, fix them in place, and drove them home with pile drivers. They were not straight up and perpendicular like piles but sloping forward so that they leaned in the direction in which the river was flowing. He placed another set of pairs, facing the first, downstream in a distance of forty feet, built in the same way but slanted against the powerful onrush of the river. On top of every pair of posts he placed at been a foot and half wide, which extended the whole distance across.  On each end a brace fastened the beams in place, keeping the two sides apart. With the sides kept apart but balanced by the countervailing forces, such was the stability of this construction, and the greater the natural forces added to it, the greater the force of the onrushing water, the more tightly the bonds held. Wood was laid over at right angles to connect these units to each other and was paved with long poles and solid wicker work panels.  Piles were also driven in downstream at a slant, as countersupports, and connected with the whole construction to absorb the force of the river. There was a similar row placed a ways upstream from the bridge, so that if tree trunks or boats were sent down by the barbarians to break up the structure, the power of these objects would be diminished by these “defenders” and they would not harm the bridge.”

Caesar’s army crossed the bridge, reconnoitered north of the Rhine for just eighteen days, then retreated back to Gaul, tearing the bridge down after their return. The book continues with a description of a brief military expedition across the English Channel to Celtic Britain. There, Caesar twice defeats the Britons, before returning to Gaul to crush new rebellions.

In Book Five, ”The Campaign of 54 BCE,” Caesar returns to Britain with a fleet estimated at 600 ships, describing how he fights his way up the Thames estuary, before moving back downriver to the coast and defeating a Celtic force, commanded by Cassivellaunus, leader of the defense of Celtic Britain. After securing concessions from the Britons, Caesar returns to Gaul to deal with a revolt by the Belgae that destroyed a Roman legion. The remainder of this book describes Caesar’s army on the defensive, but capable of defeating much larger barbarian armies due to Roman military capabilities.

LEFT: Modern recreation of the Alesia fortifications, featuring rows of stakes in front of a moat, a high banked approach, and regular towers for Roman sentries. 

Book Six, ”The Campaign of 53 BCE,” is the shortest of Caesar's books and describes in some detail the differences between Celtic and Germanic cultures, then continues with a description of barbarian revolts and how Caesar and his officers put down these revolts. He also discusses a second crossing of the Rhine, again using a temporary wooden bridge, in pursuit of retreating Suebi tribesmen. Deciding against pursuing the rebels into the Germanic forest, he returns to Gaul and defeats another rebellion.

Book Seven, ”The Campaign of 52 BCE,” is the final book penned by Caesar. An additional Book Eight was written about the campaign of 51 BCE by one of his lieutenants, Aulus Hirtius, and is often included in the translations of this text. It is the Gallic War’s longest book, and one which provides details to the climax of Caesar’s war in Gaul. Here, he describes how he and his legions manage to withstand the revolt of fourteen Gallic tribes, then counterattack and take a number of enemy fortresses, including Vellaunodunum, Cenabum, Noviodunum, and Avaricum, before a serious setback at Gergovia. The Gallic revolt spreads under the leadership of the Celtic chieftain Vercingetorix, forcing a major confrontation (a battle and a siege) at Alesia, where the Roman forces defeat the Celtic leader and accept his surrender, ending the revolt. This chapter is noteworthy due to Caesar’s detailed description of the siege at Alesia, making note of both Roman and barbarian tactics, including the Roman siege tactics of circumvallation and contravallation when hemmed in between a besieged wall and an enemy relief force.

“Caesar arrayed the entire army on the fortifications, facing in both directions: when the need arose, each man would know his position and stick to it.  He then gave orders to lead the cavalry out of the camp and to join battle.  From all of the camps, which occupied the heights on the ridge all around, the plain beneath was clearly visible, and all the soldiers expected the outcome of the battle with rapt attention.  The Gauls had inserted a few bowmen and light armed infantrymen among their cavalry; their purpose was to come to the aid of their comrades when they retreated and to hold up the assault of our cavalry. Quite a few of our horsemen were wounded in sneak attacks by these men and forced to retire from battle. As the Gauls felt confident that their side had the advantage in the fight, and saw our men were pressed hard by the size of the enemy force, on all sides by the besieged and the relief force shouted and howled war cries, cheering their fighters on. Because the drama was unfolding within sight of everyone and no action, whether worthy or shameful, could be hidden, the passion for praise and the fear of disgrace animated the fighters on both sides to excel in courageous deeds.”

RIGHT: North face of the Mausoleum of Glanum in southern France, showing a cavalry battle like the one described by Caesar in his Gallic War. The mausoleum, some 60 feet high, can be found at the beginning of the road to Arles and Nimes, and is dated to 30 to 20 BCE. The dedicatee was a warrior in the armies of Julius Caesar and/or the emperor Augustus, who awarded him with the Roman citizenship. The fourfold arch that is the lower part of the mausoleum reminds of a triumphal arch, a fitting symbol for a warrior.

Julius Caesar’s Gallic War, initially sent to Rome as propaganda to buttress his political reputation and aspirations, became popular reading material both in classical Rome and the centuries that followed. Although poorly circulated during most of the medieval era, it found new life in the Renaissance as new Latin and vernacular translation became available. Later military theorists like the Italian Niccolo Machiavelli (1469-1527) and Prussian Frederick the Great (1712-1786) cited his Gallic War in their military manuals, while his simple prose became a popular tool for learning classical Latin for centuries. For modern military historians it provides detailed information on Roman strategy, tactics, logistics, order of battle, siege capabilities and military engineering, as well as insight into the personality of one of Western Civilization’s most famous generals and statesmen.

Suggested Primary Source Readings:

Brennan, Shane, and David Thomas, ed. The Landmark Xenophon's Anabasis. Translated by David Thomas. Pantheon Books, 2021.

Strassler, Robert B., ed. The Landmark Arrian: The Campaigns of Alexander. Translated by Pamela Mensch. Anchor, 2012.

_____. The Landmark Julius Caesar: The Complete Works. Translated by Kurt A. Raaflaub. Pantheon Books, 2017.

Tacitus, Agricola and Germany. Translated by Anthony Birley. Oxford University Press, 2009.

_____. Annals of Imperial Rome. Translated by Michael Grant. Penguin Classics, 1956.

_____.The Histories. Translated by Kenneth Wellesley. Penguin Classics, 2009.