How Caesar’s Dictatorship and Gallic Conquest Changed Both Rome and Gaul

Ultimately, it allowed Caesar to overthrow the Roman Republic and led to the establishment of the Imperial system.


Julius Cesar is one of the most famous men in all of history. He was one of the greatest military commanders of all time and the man who transformed the Roman Republic into an Empire. One of Cesar’s greatest achievements was the conquest of Gaul in a series of bloody wars (57-51 BCE). This conquest was not only a remarkable achievement, but it had a profound impact on the future of Europe. It changed the balance of power within the Roman Republic.

Ultimately, it allowed Caesar to overthrow the Roman Republic and led to the establishment of the Imperial system, under his grand-nephew Octavian (Augustus). The Romanization of the Gallic provinces led to the development of Gallo-Roman culture and the end of Celtic Gaul. One of the long-term consequences of the Caesarean conquest of Gaul was that it probably saved Celtic Gaul from becoming overrun by German tribes. The conquest of Gaul confirmed that Rome was not just a Mediterranean power but a European one. After the conquest, Rome was free to take over other areas in western Europe including much of Britain.


Julius Caesar was an aristocrat and a prominent politician in Rome. He had entered an informal arrangement with Pompey and Crassus, and this had brought a measure of stability in Rome after many years of conflict. Cesar had himself appointed as commander of Roman Legions in the south of Gaul. Gaul was an area that approximated to modern France, Luxembourg, part of the Netherlands and Belgium. Gaul covered much of Western Europe. Much of the area was dominated by Celtic tribes who had developed a sophisticated political system and culture.[1] Cesar and some legions were in the south of Gaul to protect the Greek city-state of Massalia (Marseilles) from attack by Celtic tribes. Cesar was only instructed to repel any attackers, but as he was in the area, the Helvetti, from modern Switzerland, migrated into the region around Massalia.[2]

A bust of Julius Cesar /, Creative Commons

Caesar portrayed this to the Roman Senate as an invasion and attacked the Helvetti. Ultimately, Caesar drove the Helvetti back to their homeland. He then used the threat posed to some allied Gallic tribes from the Germans to justify intervention in Gaul. Caesar did not have the permission of the Senate to invade Gaul and to annex it. Indeed, the Gallic wars were started by Caesar on his initiative.[3] He wanted military glory and booty to further his political career and to pay off his many debts. Gaul now was divided among a series of tribal confederacies, even though they all considered themselves Celts.

Caesar skilfully exploited the divisions between the tribes to his advantage. Many of the Celtic tribes became his allies, such as the Aedui.[4] These allies were allowed a measure of self-rule, it seemed likely that they did not fully understand the extent of Roman ambitions in Gaul. They may have believed that Caesar would eventually leave the region. However, Caesar and the Romans were in Gaul to stay.[5] One by one, Caesar throughout five years would conquer the tribes, or they became his allies.

Caesar was a brilliant propagandist, and he had his dispatches from his campaigns read publicly in Rome. There were later collected together to form the history ‘The Gallic Wars’. Because of the war, Caesar became very rich and famous, and soon he even began to eclipse Pompey the Great. Caesar could defeat war-like tribes such as the Nervii and Belgae because of his superior tactics and the brilliance of the legions. On many occasions, he conquered significantly larger Celtic armies.[6] The Roman general cleverly exploited Celtic battle tactics for his advantage and used fixed projectile firing weapons such as the scorpion and the ballista to break up the Gauls mass charges.

By 54 BC, most of Gaul was under the control of the Romans. However, there was widespread discontent. According to Plutarch, the Celtic pagan priesthood known as the druids began to ‘incite the Celtic aristocracy against the Romans.’[7] Secretly, the Gauls united and allied with an aim toward expelling the Romans. Vercingetorix, chief of the Arverni tribe, led the many Gallic tribes and states, he proved to be a formidable general. He and his army drove the Romans from many areas.[8] They adopted guerrilla tactics and usually refused to engage the Roman legions in battle.[9]

When Caesar was besieging the Gauls at Alesia, Vercingetorix in a brilliant maneuver surrounded the Roman legions. Under any other general the Roman army would have been demolished, but Caesar successfully turned that tide and defeated the Gaul’s at Alessia. The Battle of Alesia ended the Gallic rebellion. Vercingetorix was later strangled as part of the Triumph of Caesar in Rome.[10] After his victories, Caesar typically left the local Gaul elites in power and imposed no new burdens on them. These favorable terms allowed Rome to kept Gaul (already exhausted by so many unsuccessful battles) in obedience.[11] Caesar’s victory in Gaul was total, and there was no further any attempt by the Gauls to throw off Roman rule. The area became a crucial part of the Roman Empire until the fall of the Western Empire in the mid-5th century AD.

Impact of the Conquest on Roman Politics

Vercingetorix throws down his arms at the feet of Julius Caesar. Painting by Lionel Royer (1899) / Musée Crozatier, Wikimedia Commons

The first and most immediate consequence of the war was that it upset the balance of power in Rome. The First Triumvirate was a political arrangement between Pompey, Crassus, and Cesar. This arrangement allowed the three most powerful men in Rome to achieve their respective goals. However, Crassus was killed in an ill-advised invasion of Parthia.[12] This left Pompey and Cesar as the two most powerful men in Rome.

Pompey and Caesar were not only leaders of the Triumvirate but family. Pompey had been the son-in-law of Caesar. Both Julia, Caesar’s daughter, and Pompey’s wife, died in childbirth. Her death weakened the alliance between the two men. Many regarded Cesar as a war-monger in the Roman Senate and believed that he was engaged in an illegal war in Gaul.[13] The Roman senators were not concerned with the fate of the Gauls but were extremely suspicious of Caesar’s motives. They believed that he was building up a power base in Gaul and he was treating the legions under his command as his private army.

The senators feared that Cesar would seize power and become a dictator just as Sulla had. Many of the Roman elite were suspicious of Cesar because of his close connections with Marius and the popularas party. During the war, Caesar had been able to retain control of his legions because he claimed that they were needed in the conquest of Gaul.[14] With the end of the conflict, he was not supposed to retain control of his army.

The Senate after Cesar’s great victory at Alessia demanded that he return to Rome and that he give up command of his legions. The Senate had the law on its side, but Caesar was worried that if he did give up his legions that he would be vulnerable to his Roman enemies. Caesar demanded that he be given an extraordinary command and that he be allowed to command some legions. Pompey sided with the Senate, and he began to regard Cesar as his enemy.[15]

The Senate rejected Caesar’s proposal. Caesar, bold as ever, tried to force the issue and marched his legions on Rome. Caesar claimed that there was a conspiracy against him ‘it was evident to everyone that war was designed against Caesar.’[16] When he ordered his legionnaires to cross the River Rubicon, he defied the Senate and this made Civil War inevitable. The Gallic Wars made Cesar the most powerful man in Rome, and this resulted in a civil war. Caesar used his legions of battle-hardened veterans to defeat Pompey and the Republican army at Pharsalus.[17] This civil war led the ascent of Caesar as the sole power of Rome. Caesar’s Gallic Wars were an important stage in the final downfall of the Roman Republic.[18]

Impact of the Conquest on the Gauls

A reconstructed section of the Alesia investment fortifications / Wikimedia Commons

Caesar destroyed the Celtic civilization in Gaul. The Celtic priesthood, the druids, were key to the culture and religion of Gaul. The Gauls, despite their sophistication, were a pre-literate people, although some used Greek for official purposes. The Druids were renowned for their remarkable memories, and they retained the oral history of the Gauls. The druids were also the judicial class, and they alone could remember the legal codes of the various tribes.[19] The priestly class also played a significant role in the oral literature of the Celts.

The druids were among the fiercest opponents of the Romans, and Caesar recognized them as one of the primary obstacles to his conquest of Rome. The Romans also hated the druids because they allegedly practiced human sacrifice as part of their religion. Caesar targeted the druids during his war with the Gallic tribes. In his history of the Gallic Wars, he reported that his armies would often target the sacred groves of the Druids and killed many of these priests. He justified this violence because he argued that they were barbarians who engaged in bloody rites and ceremonies.[20] Caesar eliminated the druids and destroyed their shrines and sanctuaries.

As the druids disappeared, the Celtic religion and culture rapidly decline. Trade between Gaul and Rome increased, and the Romans imposed their laws on Gauls. The increased trade transformed the province and it quickly Romanized. The old Gallic elite soon began to imitate the Romans, and many learned Latin. Soon Roman-style villas dotted the Gaulish landscape. By the first century AD, the Gallic elite was so Romanized that some were admitted into the Senate by Emperor Claudius.[21]. Many historians believe that Celtic Gaul was doomed anyway and that the German tribes would have conquered it. Around the time of the Roman invasion, many German tribes were raiding and even settling in Gaul. One of the justifications that Caesar used for his war was that he sought to protect Roman interests in Gaul from the Germans.

Consequences of the Conquest of Gaul

By conquering Gaul, Caesar greatly expanded the influence of Rome in Western Europe. Before this conquest, the Roman Republic had been centered on the Mediterranean. Caesar transformed Rome into a European power. Suddenly Rome’s influence was no longer centered on the Mediterranean, and this had important consequences for its future expansion. Even before the Gallic campaign was over, Rome had turned its attention to other areas of western and central Europe. Caesar raided Britain in 55 BC and crossed the Rhine and fought a war with the powerful Suebi tribe a year later.

Roman Emperors followed the example of Caesar and tried to expand their Empire in Europe. Emperor Augustus invaded Germania and conquered most of the area, right up to the River Elbe. However, this resulted in a great rebellion and the loss of three legions in Teutoburg Forest. This defeat led to Augustus setting the border with Germania at the Rhine. He did manage to retain the Rhineland for the Roman Empire. Claudius had better luck. He successfully conquered most of Britain apart from Scotland in the First Century AD. The future expansion of the Roman Empire would not have been possible without the conquest of Gaul. Caesar inspired future leaders to try and conquer more land in western Europe. The great Roman historian Tacitus related how Claudius, over 100 years later, felt duty bound to invade further into Britain and complete the work of Caesar.[22]


The conquest of Gaul by Caesar was to have momentous consequences. It resulted in a large area of western Europe coming under the sway of the Romans. From Gaul, they could expand their empire into parts of Germany and Britain. The Roman province of Gaul was to remain part of the Roman Empire until the 450 AD. The conquest of Roman changed the character of Gaul and led to the decline of the local Celtic civilization, and the rise of a Romano-Gallic culture. This culture played a critical role in the development of the kingdom of France during the Middle Ages. If Caesar had not conquered, the Germanic tribes might have completely overrun Gaul.

Perhaps the most immediate consequence of the conquest of Gaul was that it upset the balance of power in Rome. It led to a confrontation between Cesar and the Roman Senate over control of the legions in Gaul, and this led to a civil war. Over the long term, this was to result in the heir of Caesar becoming the first Emperor of Rome. It could be argued that the most dramatic consequence of the Roman victories in Gaul was that they ultimately led to the emergence of the Imperial system in Rome.



  1. Caesar, Gallic Wars. 1.1
  2. Goldsworthy, Adrian. Julius Caesar (London, Orion, 2007), p. 119
  3. Holland, Tom. Rubicon (London, Longman, 2005), p 167
  4. Caesar, Gallic Wars, 3. 34
  5. Goldsworthy, p. 218
  6. Holland, p 198
  7. Plutarch. Life of Caesar. 15
  8. Caesar, 8. 16
  9. Caesar. 8 2
  10. Plutarch. Life of Caesar. 16
  11. Cesar, 8.49
  12. Plutarch. The Life of Crassus. 5
  13. Holland, p. 178
  14. Holland, p 214
  15. Goldsworthy, p 278
  16. Cesar, 8 55
  17. Holland, p. 278
  18. Plutarch. Life of Augustus 15
  19. Holland, p. 213
  20. Caesar,, 7. 34
  21. Tacitus. Annals. 6. 45
  22. Tacitus. 8. 45


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