What was the impact of Cesar's conquest of Gaul on Rome and its empire?


Julius Cesar is one of the most famous men in all of history. He is widely regarded as one of the greatest military commanders of all time and the man who helped to transform 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 was not only a remarkable achievement but it also transformed the Roman Empire and was to have profound consequences for the future of Europe. It also changed the balance of power within the Empire and ultimately allowed Cesar to overthrow the Roman Republic and to this led to the establishment of the Imperial system, under his grand-nephew Octavian, later known as Augustus. The Romanization of the Gallic provinces led to the development of a 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 was to turn the Roman Empire from a Mediterranean power but into a European power. It enabled the Romans to conquer other areas in western Europe, in particular, much of what is modern Britain.

A bust of Julius Cesar


Julius Cesar 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. In fact, 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]. Cesar portrayed this to the Roman Senate as an invasion and attacked the Helvetti and drove them back to their homeland. He then used the threat posed to some allied Gallic tribes from the Germans to justify intervention in Gaul. Cesar did not have the permission of the Senate to invade Gaul and to annex it, indeed the Gallic wars as they came to be called, were started by Cesar on his own 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 for his own advantage. Many of the Celtic tribes became his allies, such as the Aedui [4]. These allies were allowed a measure of self-rule, it seems likely that they did not know the Romans ambitions in Gaul and believed that Caesar would eventually leave the region. However, Caesar and the Romans were in Gaul to stay[5]. One by one, Caesar over a period of five years could 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, Cesar became very rich and popular 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 defeated much larger Celtic armies [6]. The Roman general cleverly exploited Celtic battle tactics for his own advantage and use 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 the druids began to ‘incite the Celtic aristocracy against the Romans’ [7]. Secretly, the Gaul’s united and formed an alliance with the aim of 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 legions in battle [9]. When Cesar 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 annihilated. Caesar could decisively defeat the Gaul’s at Alessia and after this, the great Gallic rebellion was over. Vercingetorix was later strangled as part of the Triumph of Caesar in Rome [10]. After his great victory Cesar usually left the local elite in power and ‘imposing no new burdens, and making the terms of their subjection lighter, he easily 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 Gaul’s to throw off Roman rule and the area became a key 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

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 had been the son-in-law of Cesar. Julia the daughter of Cesar and Pompey’s wife had died in childbirth and this 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 Gaul’s but rather were suspicious of the motives of Cesar. 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 dictator just as Sulla had. Many of the Roman elite were suspicious of Cesar because of his close connections with Marius and the popular part. During the war, Cesar, had been able to retain control of his legions because he claimed that they were needed in the conquest of Rome[14]. With the end of the conflict he could not continue to do this. 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 Cesar was worried that if he did give up his legions that he would be vulnerable to his enemies. Cesar 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 this and Cesar, bold as ever, tried to force the issue and marched his legions on Rome. Cesar, to justify his actions 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. Cesar used the legions that conquered Gaul, battle-hardened veterans to defeat Pompey and the Republican army at Pharsalus[17]. These civil wars were to finally result in the establishment of the Imperial system under Cesar’s heir, Augustus and the end of the Roman Republic. Cesar’s Gallic Wars were an important stage in the final downfall of the Roman Republic[18].

Julius Cesar receiving the surrender of the Gallic leader after Alesia

Impact of the Conquest on Gaul

Cesar destroyed the Celtic civilization in Gaul. The Celtic priesthood the druids were key to the culture and religion of Gaul. The Gaul’s 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 could retain and remember the oral history of the Gauls. The druids were also the judicial class and they alone could remember the law codes of the various tribes [19]. The priestly class also played a very important 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 main obstacles to his conquest of Rome. The Romans also hated the druids because they allegedly practised human sacrifice as part of their religion. Caesar target the druids during his war with the Gallic tribes. In his history of the Gallic Wars he reports that his armies would often attack the sacred groves of the Druids and they killed many of these priests. He justified this because they were barbarian who engage in bloody and ‘superstitio’ or superstitious rites and ceremonies[20]. Caesar eliminated the druids and destroyed their shrines and sanctuaries. With the demise of the druids the Celtic religion and culture went into a rapid decline in Gaul. Trade between Gaul and Rome increased and the Romans imposed their laws on Gauls. This transformed the province and it quickly began to Romanize. The old Gallic elite soon began to imitate the Romans and many learned Latin and soon Roman-style villas dotted the landscape. By the first century AD, the Gallic elite were so Romanized that some were admitted into the Senate by the Emperor Claudius[21]. Many historians believe that Celtic Gaul was doomed anyway and that it would have been conquered by the German tribes. Around the time of the Roman invasion many German tribes were raiding and even settling in Gaul. One of the justifications that Cesar used for his war was that he sought to protect Roman interests from the Germans. It seems likely that if the Romans had not conquered Gaul that it would have been conquered by the Germans and become Germanic in culture and religion.

Recreation of Roman fortifications in Gaul

Consequences of the Conquest of Gaul

The Roman Empire was greatly expanded by the conquest of Caesar. Before this the Empire was mainly centred on the Mediterranean and Rome had been a Mediterranean power. The conquest of Gaul changed all of this. Suddenly Rome’s Empire was no longer centred on the Mediterranean and this had important consequences for its future expansion. The Romans even during the Gallic campaign turned their 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. The 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 Teutenbourg Forest. This 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 and he successfully conquered most of Britain apart from Scotland in the First Century AD. The future expansion of the Roman Empire would have been possible without the conquest of Gaul. Caesar inspired future leaders to try and conquer more land in western Europe and without his example, Britain for example would not have been conquered by the legions of Claudius. The great Roman historian relates how Claudius felt duty bound to invade Britain and complete the work of Cesar[22].


The conquest of Gaul by Cesar 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 it led to the decline of the local Celtic civilization and the rise of a Romano-Gallic culture. This culture was to play a very important part in the development of the kingdom of France in the Middle Ages. It seems that if it had not been for Cesar that the Germans would have 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 Cesar 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. Cesar, Gallic Wars. 1.1
  2. Goldsworthy, Adrian. Julius Cesar (London, Orion, 2007), p. 119
  3. Holland, Tom. Rubicon (London, Longman, 2005), p 167
  4. Cesar, Gallic Wars, 3. 34
  5. Goldsworthy, p. 218
  6. Holland, p 198
  7. Plutarch. Life of Cesar. 15
  8. Cesar, 8. 16
  9. Cesar. 8 2
  10. Plutarch. Life of Cesar. 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. Cesar, 7. 34
  21. Tacitus. Annals. 6. 45
  22. Tacitus. 8. 45