The military campaigns of Julius Caesar were a series of wars that reshaped the political landscape of the Roman Republic, expanded its territories, and ultimately paved the way for the transition from republic to empire. The wars constituted both the Gallic Wars (58 BC–51 BC) and Caesar's civil war (49 BC–45 BC).
The Gallic Wars principally took place in the region of Gaul, or what is now modern-day France. These campaigns, starting with the Battle of the Arar (Saône) River, were conducted between 58 and 50 BC. Caesar faced formidable resistance from Gallic chieftains such as Vercingetorix and Dumnorix.Julius Caesar, Gallic war, Edited and Translated by Cynthia Damon, Loeb classical library, Harvard University press, on pg 13: Dumnorix is talked about as a chieftain (as he is, specifically of the adeuan people) and a "very potent force among the Sequani People." Despite numerous challenges, Caesar and his legions managed to conquer the territories and incorporate them into the Roman Republic. During the campaigns in 55 and 54 BC, Caesar invaded Britain, marking the first Roman expeditions to the island. These campaigns were characterized by fierce battles against various Celtic tribes. The Gallic War ended with Roman victory at the Battle of Alesia.
During the Civil War, Caesar pursued his rivals to Greece, where he engaged in a series of decisive confrontations, and solidified Roman control over the Eastern Mediterranean. These battles, notably the Battle of Pharsalus in 48 BC, marked significant turning points in the conflict, ultimately leading to Caesar's triumph over the forces of Pompey the Great.
He proceeded to Egypt, where he emerged victorious against the Egyptian pharaoh, facilitating the ascension of Cleopatra to the throne. He then went on to subdue his Roman opponents in Africa and Hispania. Once his campaigns were concluded, he served as Roman dictator until his assassination on 15 March 44 BC.
These wars were critically important in the transition of the Roman Republic into the Roman Empire.
Early military career
Gaius Julius Caesar was born into an influential patrician family, the gens Julia. His father, Gaius Julius Caesar, was the governor of the province of Asia, and his mother, Aurelia, came from an influential family who were supporters of Sulla. In 85 BC, at the age of 16, Caesar became the head of his family after his father’s death, which coincided with the civil war between Sulla and supporters of Caesar's uncle Gaius Marius. When Marius and his ally Lucius Cornelius Cinna were in control of Rome, Caesar was nominated as the new flamen Dialis (high priest of Jupiter), and he was married to Cinna's daughter Cornelia. After Sulla's ultimate victory, he enacted a brutal purge of the supporters of Marius, including Caesar. He was stripped of his inheritance, his position of high priest and was forced to go into hiding after refusing to divorce Cornelia. Sulla eventually ended his persecution of Caesar after his mothers family intervened on his behalf. Soon after this, Caesar entered into service in the army in 81 BC in an attempt to leave Rome should Sulla change his mind.
He first served under the command of Marcus Minucius Thermus in Asia and Servilius Isauricus in Cilicia. He won early distinction by earning the Civic Crown for his actions at the Siege of Mytilene and later secured the assistance of King Nicomedes's fleet during a diplomatic mission to Bithynia.
After Sulla's death in 78 BC, Caesar returned to Rome where he was elected military tribune. This served as his entry into politics and in 69 BC, he was elected as quaestor in the province of Hispania. He was also elected to Pontifex maximus and was eventually made governor of Hispania Ulterior. While in Hispania, Caesar held the title of Imperator and lead military campaigns against local tribes.
Three candidates stood for the consulship in 59 BC: Caesar, Marcus Calpurnius Bibulus who had been aedile with Caesar several years earlier, and Lucius Lucceius. The election was dirty. Caesar canvassed Cicero for support, and made an alliance with the wealthy Lucceius, but the establishment threw its financial weight behind the conservative Bibulus, and even Cato, with his reputation for incorruptibility, is said to have resorted to bribery in his favor. Caesar and Bibulus were elected as consuls.Plutarch, Caesar 13–14; Suetonius 19
Caesar was already in Crassus' political debt, but he also made overtures to Pompey, who was unsuccessfully fighting the Senate for ratification of his eastern settlements and farmland for his veterans. Pompey and Crassus had been at odds since they were consuls together in 70 BC, and Caesar knew if he allied himself with one he would lose the support of the other, so he endeavored to reconcile them. Between the three of them, they had enough money and political influence to control public business. This informal alliance, known as the First Triumvirate (rule of three men), was cemented by the marriage of Pompey to Caesar's daughter Julia.Cicero, Letters to Atticus 2.1, 2.3, 2.17; Velleius Paterculus, Roman History 2.44; Plutarch, Caesar 13–14, Pompey 47, Crassus 14; Suetonius, Julius 19.2; Cassius Dio, Roman History 37.54–58 Caesar also married again, this time Calpurnia, daughter of Lucius Calpurnius Piso Caesoninus, who was elected to the consulship for the following year.Suetonius, Julius 21
Caesar proposed a law for the redistribution of public lands to the poor, a proposal supported by Pompey, by force of arms if need be, and by Crassus, making the triumvirate public. Pompey filled the city with soldiers, and the triumvirate's opponents were intimidated. Bibulus attempted to declare the omens unfavorable and thus void the new law, but was driven from the forum by Caesar's armed supporters. His lictors had their fasces broken, two tribunes accompanying him were wounded, and Bibulus himself had a bucket of excrement thrown over him. In fear of his life, he retired to his house for the rest of the year, issuing occasional proclamations of bad omens. These attempts to obstruct Caesar's legislation proved ineffective. Roman satirists ever after referred to the year as "the consulship of Julius and Caesar".Cicero, Letters to Atticus 2.15, 2.16, 2.17, 2.18, 2.19, 2.20, 2.21; Velleius Paterculus, Roman History 44.4; Plutarch, Caesar 14, Pompey 47–48, Cato the Younger 32–33; Cassius Dio, Roman History 38.1–8
This also gave rise to this lampoon:
The event occurred, as I recall, when Caesar governed Rome-
Caesar, not Bibulus, who kept his seat at home.
When Caesar and Bibulus were first elected, the aristocracy tried to limit Caesar's future power by allotting the woods and pastures of Italy, rather than governorship of a province, as their proconsular duties after their year of office was over.Suetonius, Julius 19.2 With the help of Piso and Pompey, Caesar later had this overturned, and was instead appointed to govern Cisalpine Gaul (northern Italy) and Illyricum (the western Balkans), with Transalpine Gaul (southern France) later added, giving him command of four legions. The term of his pro-consulship, and thus his immunity from prosecution, was set at five years, rather than the usual one.Velleius Paterculus, Roman History 2:44.4; Plutarch, Caesar 14.10, Crassus 14.3, Pompey 48, Cato the Younger 33.3; Suetonius, Julius 22; Cassius Dio, Roman History 38:8.5 When his consulship ended, Caesar narrowly avoided prosecution for the irregularities of his year in office, and quickly left for his province.Suetonius, Julius 23
Conquest of Gaul
Caesar was still deeply in debt, and there was money to be made as a provincial governor, whether by extortionSee Cicero's speeches against Verres for an example of a former provincial governor successfully prosecuted for illegally enriching himself at his province's expense. or by military adventurism. Caesar had four legions under his command, two of his provinces, Illyricum and Gallia Narbonensis, bordered on unconquered territory, and independent Gaul was known to be unstable. Rome's allies the Aedui had been defeated by their Gallic rivals, with the help of a contingent of Germanic Suebi under Ariovistus, who had settled in conquered Aeduan land, and the Helvetii were mobilizing for a mass migration, which the Romans feared had warlike intent. Caesar raised two new legions and defeated first the Helvetii, then Ariovistus, and left his army in winter quarters in the territory of the Sequani, signaling that his interest in the lands outside Gallia Narbonensis would not be temporary.Cicero, Letters to Atticus 1.19; Julius Caesar, Commentaries on the Gallic War Book 1; Appian, Gallic Wars Epit. 3; Cassius Dio, Roman History 38.31–50
Caesar began his second year with double the military strength of the previous year, having raised another two legions in Cisalpine Gaul during the winter. The legality of this was dubious, as the Cisalpine Gauls were not Roman citizens. In response to his activities the previous year, the Belgic tribes of north-eastern Gaul had begun to arm themselves. Caesar treated this as an aggressive move and, after an inconclusive engagement against a united Belgic army, conquered the tribes piecemeal. Meanwhile, one legion, commanded by Crassus' son Publius, began the conquest of the tribes of the Armorican peninsula.Julius Caesar, Commentaries on the Gallic War Book 2; Appian, Gallic Wars Epit. 4; Cassius Dio, Roman History 39.1–5
During the spring of 56 BC a conference was held at Luca (modern Lucca) in Cisalpine Gaul. Rome was in turmoil, and Clodius' populist campaigns had been undermining relations between Crassus and Pompey. The meeting renewed the Triumvirate and extended Caesar's proconsulship for another five years. Crassus and Pompey would be consuls again, with similarly long-term proconsulships to follow: Syria for Crassus, the Hispanian provinces for Pompey.Cicero, Letters to his brother Quintus 2.3; Suetonius, Julius 24; Plutarch, Caesar 21, Crassus 14–15, Pompey 51 The conquest of Armorica was completed when Caesar defeated the Veneti in a naval battle, while young Crassus conquered the Aquitani of the south-west. By the end of campaigning in 56 BC only the Morini and Menapii of the coastal Low Countries still held out.Julius Caesar, Commentaries on the Gallic War Book 3; Cassius Dio, Roman History 39.40–46
In 55 BC, Caesar repelled an incursion into Gaul by the Germanic Usipetes and Tencteri, and followed it up by building a bridge across the Rhine and making a show of force in Germanic territory, before returning and dismantling the bridge. Late that summer, having subdued the Morini and Menapii, he crossed to Britain, claiming that the Britons had aided the Veneti against him the previous year. His intelligence was poor, and although he gained a beachhead on the Kent coast he was unable to advance further, and returned to Gaul for the winter.Julius Caesar, Commentaries on the Gallic War Book 4; Appian, Gallic Wars Epit. 4; Cassius Dio, Roman History 47–53 He returned the following year, better prepared and with a larger force, and achieved more. He advanced inland, establishing Mandubracius of the Trinovantes as a friendly king and bringing his rival, Cassivellaunus, to terms. But poor harvests led to widespread revolt in Gaul, led by Ambiorix of the Eburones, forcing Caesar to campaign through the winter and into the following year. With the defeat of Ambiorix, Caesar believed Gaul was now pacified.Cicero, Letters to friends 7.6, 7.7, 7.8, 7.10, 7.17; Letters to his brother Quintus 2.13, 2.15, 3.1; Letters to Atticus 4.15, 4.17, 4.18; Julius Caesar, Commentaries on the Gallic War Book 5–6; Cassius Dio, Roman History 40.1–11