Background of Caesar's Gallic Wars

Romans and Gauls had been conflicting for centuries prior to the conquest of Gaul in the 1st century BC, but for long times they had also experienced relative peace as neighbors or near neighbors. Celtic or Gallic tribes (as the Greek writers called them) migrated into northern Italy during the late 5th and early 4th centuries BC, with some tribes settling, mainly around the fertile Po valley. The first major encounter between Rome and these Celtic tribes of what is called as the La Tène culture, came in the early 4th century BC. They enter south into Latium and Etruria (Lazio and Toscana) where the invaders captured and sacked a number of the largest cities, including the important Etruscan center of Veii only a few miles north of Rome.   In 390 BC Rome's field forces were defeated, and the poorly defended city captured by the Gauls. Only the citadel held out: according to tradition, when the Gauls tried to scale it in a surprise night attack, the guard dogs failed to bark and it was only the honking of geese (kept on the Capitol because they were sacred to Jupiter) that awoke the guards. The guards then repelled the attack. The story may not he true, but after sacking Rome, or being paid off by the Romans, the Gauls withdrew. They were defeated soon afterwards by Camillus, the great Roman general who is traditionally recognized by making fundamental changes to the Roman army in order to deal with this new Gallic threat. The sacking of Rome was never forgotten, and Romans remained haunted by a kind of collective inherited fear of hordes of barbarians returning to destroy the city. The sack, along with the long subsequent history of violent encounters between the two cultures, formed part of the background to Caesar's conquest of Gaul.

During the 150 years after the sack, Rome was progressively able to establish superiority over much of the Italian peninsula, ejecting several of the Gallic tribes from lands to the north of Rome. Between the First and Second Punic Wars (during the 3rd century BC this conquest of Italy extended to the north as a coalition of Gallic tribes from northern Italy and across the Alps moved south, only to suffer a devastating defeat at Telamon in 225 BC which broke Gallic resistance in Italy. In the next five years the majority of the territory beyond the Po was incorporated as the province of Cisalpine Gaul, and Roman colonies were founded at Cremona and Piacenza. The final reduction of this new province had to wait until after the Second Punic War and the repulse of the Carthaginian raiding forces under Hannibal. After the first big Roman defeat at the hands of Hannibal at the Trebia in 218 BC, Gallic mercenaries flocked to join Hannibal and served with him through much of the Italian campaign. But after defeating Carthage, Rome turned back to north ltaly and punished the tribes who had fought against them. The whole of ltaly as far north as the Alps was incorporated as Roman territory and further colonies were created at Parma and Bologna. By the middle of 2nd century BC Rome was ready to move into France, having secured her occupation of the whole of Cisalpine Gaul.

Detail from the Altar of Domitius Ahenabarbus, a st century BC relief illustrating the taking of a census which included details of the military liability to every citizen. The two soldiers represent the link between citizen status and military service. (Ancient Art and Architecture)

The reason came in 154 BC when the Greek city of Marseilles requested help from Rome against raids from Liguria. The Roman response included the establishment of a small veteran settlement at Aix en Provence, which irritated the powerful Alloboges tribe nearby, on whose territory it was founded. The Alloboges and their allies, including the Arverni, were defeated in a series of campaigns fought by Fabius Maximus  and Domitius Ahenobarbus. Fabius inflicted an appalling defeat on the Gauls in 121 BC, claiming the quite extraordinary (and highly unlikely) casualty figures of 120,000 Gallic dead to only 15 Roman. The new province of Transalpine Gaul was created, which the Romans frequently referred to as simply 'The Province', from which modern Provence gets its name. As in Cisalpine Gaul, colonies were founded, at Toulouse and Nimes, and a road was built, the Via Domitia, linking Italy with Spain. As well as leading to the creation of another province, the campaign to assist Marseilles also brought Rome into alliance with the Aedui, a Gallic tribe of modern Burgundy who were also allied to Marseilles. The existence of the new province and a formal alliance with the Aedui give Rome with opportunities for further intervention in Gaul and the affairs of the Gallic tribes, but any Further expansion was brought to a sudden stop by the arrival in southern Gaul of the Cimhri and Teutones. These migrating Germanic tribes give serious resistance to Rome, defeating successive consular armies in the late 2nd century BC. They were eventually beaten by Marius (a great Roman general and consul), but as with the Gallic sack of 390 BC, the experience left scars on the Roman psyche. Future Roman attacks and campaigns against Germanic tribes could be passed off as revenge for the defeats and casualties of the 2nd century incursions.

By the 1st century BC several tribes in Gaul were becoming urbanized, especially those in the south where they came under the cultural influence of Marseilles and then, with the establishment of the province of Transalpine Gaul, Rome. Although Caesar uses the word oppidum to describe hill forts, he also uses it for defended settlements that were not on hills. Some of these could have been described as towns even by Romans who might have regarded Gaul and nearly everything about it and its inhabitants as barbaric. Avaricum (Bourges) had an open space which Caesar called a forum and may have had civic buildings; it had a huge defensive wall and its inhabitants regarded it as the most beautiful city in Gaul. Cenabum (Orleans) had a series of narrow streets which may well have had some kind of plan to them: Gallic towns were starting to adopt the grid plans of Mediterranean cities. Evidence of coin manufacture at important oppida suggests that they may have been tribal capitals, indicating some degree of political centralization; Bibracte, for example, seems to have been the 'capital' of the Aedui, who were a fairly centralized tribe although plagued by factions. Other tribes that lacked this degree of centralization might have been considered culturally backward by the Romans, but this added to their military reputation: Caesar considered the Belgae to be the bravest warriors of the Gauls because they were furthest removed from Roman influence. Their lack of centralization also meant that they could be harder to conquer, as Caesar was to find when fighting tribes like the Veneti and Menapii who had no single center of occupation and wealth.

One of the main reasons for the Roman and Greek influence on the Gallic tribes was trade. Marseilles was a significant center of trade, and though Gallic tribes and Rome frequently clashed each other, that did not prevent a huge amount of trade taking place between them well prior to the conquest under Caesar. Romans imported raw materials from Gaul, including iron, grain, hides and, particularly, slaves, the source of the latter being regular inter-tribal warfare that occur between both Gallic and Germanic tribes. In exchange, the Gauls (or at least the Gallic elite) received luxury goods and foods, and enormous amounts of wine. Wine had become a key symbol of wealth, status and 'civilisation', though the historian Diodorus Siculus says that the Gauls drank it neat, rather than diluted with water in the Roman style. Hence, although they were adopting the 'civilized' customs of the Mediterranean, Diodorus makes it clear that they were still barbarians because they did not know how to drink it properly. He goes on to say that wine had become such a valuable commodity that the exchange rate for an amphora of wine was one slave, although there were certainly plenty of slaves around. There must have been many Roman merchants already in Gaul before Caesar's campaigns, including a community of citizens at Cenabum. Some of them were of high status and belonged to the Roman 'equestrian' order, the influential class immediately below senatorial rank, itself a prime source of new senators. They might expect to benefit from the opportunities conquest would bring, especially if they provided assistance in the form of intelligence and supplies for the Roman army.

A sliver coin of the Aeduan leader Dumnorix. The coin shows an Aeduan warrior with a boar standard. Whilst the Aedui were allied to Rome, there were anti-Roman elements within the tribe led by the aristocratic druid Dumnorix, who Caesar called as 'a man of boundless daring'. (AKG Berlin)

Many of the tribes that had come under greater influence from the Roman and Greek cultures to the south were ruled by oligarchies with annually appointed magistrates. The spreading centralization and tendency towards urbanization made such tribes easier targets for Rome, and internal factions within them helped the Romans too. In the mid-1st century BC the Aedui were divided between a pro-Roman faction under Diviciacus, and those who opposed the Romans led by his brother Dumnorix. Dumnorix held a monopoly over the wine trade on the Saône, a tributary of the Rhône. and probably resisted the growing Roman influence for economic as well as political reasons. His influence came from his wealth and his position as a druid: druids held high social status in Celtic society which could bring them political influence. According to the account by Caesar, Dumnorix was attempting to increase his power-base within the Aedui not just because he was opposed to the tribe's pro-Roman stance, but because he was keen to seize power and make himself king. It was important for Rome that the Aedui remained a united and powerful ally of Rome among the Celtic tribes of Gaul, and the squabbling between the two brothers must have given Rome cause for concern.
But the Aedui were coming under pressure from other tribes in Gaul in the 1st century BC. They were a powerful tribe with other lesser tribes under their protection and they had a long-standing rivalry with their neighbors, the Arverni. This rivalry came to a head in 71 BC when the Amerni attacked, along with their allies the Sequani, and German mercenaries from the Suebi whom the Sequani had rather foolishly invited in.  Once the Aedui were defeated the German mercenaries under their king Ariovistus turned on their erstwhile allies and seized much of the Sequanian territory. These events had several consequences. Rome failed to assist her ally, the Aedui, which must have damaged her reputation amongthe Gallic tribes, and Germans were now settling in Gaul near the territory of the Helvetii. This must have seriously worried the Helvetii who had already been forced into Switzerland by earlier migrations of Germanic tribes and they prepared to evacuate their homelands and migrate themselves, to western France.
In 61 BC the Roman senate had confirmed its support for the Aedui, but still failed to act. Romans were expecting some kind of involvement with Gaul in 60 BC though, perhaps military support for the Aedui. Probably because of concern about the huge migration which was obviously about to take place, preparations were made in Rome, including the holding of a levy. During his consulship in 59 BC Julius Caesar had bought off the Suebic king Ariovistus bydiplomatic gifts and the title of Friend of the Roman People. It was not an unusual move for a leading politician to make alliances with kings outside the Roman empire, especially kings of neighbouring territories who might supply additional troops for a campaign. During his year as Consul, Caesar also engineered for himself the appointment as governor of Cisalpine Gaul and Illyricum (the Adriatic coast of Dalmatia); when at the end of the year the governor of Transalpine Gaul suddenly died, Caesar was given that command as well. The forces under his command consisted of one legion based in Transalpine Gaul and three more legions that were in garrison at Aquileia in north-east Italy, based there because of the potential threats from Ariovistus and the Helvetii to the north and the Dacians to the north-east. Caesar may have been planning a campaign against Illyricum initially, but the late addition of Transalpine Gaul to his command opened up a better option.

A barge bang pulled upriver by manpower: Many of Gauls rivers were navigable and provided excellent trade routes, and supply and communication conduits for the invading Roman army Gaulish leader were keen to import luxury goods, such as wine. in return for raw materials such as iron, grain and slaves

Caesar was an ambitious politician and in order to dominate politics as a senator in Rome in the 1st century BC, it helped to be extremely wealthy (to bribe the electorate). to have a great military reputation. Of his two allies and rivals, Marcus Crassus was fabulously rich, and Pompey was both wealthy and Rome's leading general after conquering much of Spain and Turkey. On his appointment as governor of Cisalpine and Transalpine Gaul, Caesar was pretty much broke and had had little opportunity to establish himself as an able general. Conquest of a new province would allow him both to enrich himself and impress the public in Rome with his military ability. There was no doubt at all that Caesar would campaign somewhere and conquer a new province. either on the eastern Adriatic coast or in Gaul. It just happened that there were two convenient pretexts for launching operations in Gaul: the Helvetii began their migration just as Caesar was taking over command, and there was still the matter of Rome's previous failure to support their allies the Aedui. If they requested assistance, particularly against the German King Ariovistus, Caesar could justifiably intervene. At the start of 58 BC the new governor of Cisalpine and Transalpine Gaul was still in Rome when news arrived of the movement of the Helvetian tribes.

References

Gilliver, K. (2003). Caesar's Gallic Wars. New York: Osprey Publishing Ltd.