
Map of Julius Caesar's Gallic campaigns from 58 to 51 BC
The Celtic genocide occurred from 58 to 51 BC during Julius Caesar's Gallic Wars, during which two-thirds of Gaul's population was killed or enslaved by the invading Romans, and Gaul's Celtic culture was mortally wounded. The term "Celtic Holocaust" was popularized by the podcaster Dan Carlin in a 2017 podcast, in which he made the case that the Roman Republic's actions during the Gallic Wars constituted a genocide. Of the 3,000,000 Celts who inhabited ancient Gaul, one million of them were massacred, while another million were enslaved; this signifies that Gaul lost two-thirds of its population in a case of bellum romanum ("war in the style of the Romans", or total war).
Background[]

The Gauls were a strong and tall race, standing at around 6 feet tall, an extraordinary height in the ancient world. Roman civilization had always looked down on the alien Gauls, with Strabo calling them "war-mad"; even though the threat of Gallic invasion had faded centuries earlier, the scars left by the Battle of the Allia on 18 July 390 BC and the ensuing sack of Rome had ingrained the Romans with a hatred for the Gauls. The Roman historians recorded the Gallic chieftain Brennus as declaring vae victis ("woe to the vanquished") during his sack of Rome, and the Romans may have been motivated to wage total war against the barbarian tribes by this same philosophy.
In 63 BC, the Gallic world had been thrown into chaos when the Sequani and Arverni decisively defeated the Aedui at the Battle of Magetobriga, slaughtering their nobility. The Arverni and Sequani had solicited the assistance of the Germanic Suebi and other German peoples (some of whom were identified as "Celts" by the Romans) and decimated the Aedui on the battlefield, destroying their entire aristocratic class in the stroke of a sword. The Aedui druid Diviciacus pled for Roman support when the Germans decided to remain in Gaul and become the neighbors of the Celtic people around them. A destabilized Gaul proved to be a dangerous situation for Rome, but it also had the potential to be a profitable opportunity. Julius Caesar built a case for Roman intervention, claiming that Italian wine merchants saw Gaul as a land of opportunity, as the Celts were said to be drunkards who gave a slave in exchange for each jar of alcohol. Caesar would go on to campaign in Gaul with the goal of ending the warfare in the region, but he did so in a way which could be interpreted as a "Celtic Holocaust".
The Gallic tribes were not as uncivilized as the Romans believed, as many of them were highly-organized. The Gallic tribes consisted of clans, and some Gallic tribes functioned as states; the Aedui had a similar style of government as the Romans, as they also had one-term-limited leaders (similar to consuls) with the goal of preventing a clan from monopolizing power. The Helvetii tribe, meanwhile, was governed by magistrates, and they burned to death anyone who attempted to restore the monarchy. Caesar saw the Gauls as prone to fighting both individually and collectively, and also saw them as being prone to random outbursts of violence. Thus, he believed that he had to respond preemptively. He also saw the semi-civilized Gauls as a special threat, as their similarity to the Romans was growing, and he believed that their threat would increase if they were not immediately conquered. Gaul provided a great opportunity to acquire land and slaves, so Caesar was determined to conquer them and claw his way to the top of the Roman merit-based system.
Genocide[]
Defeat of the Helvetii[]

Celtic dead at the Battle of the Arar
The first major instance of the "Celtic genocide" was the Battle of the Arar in 58 BC, which was much less a battle than a massacre of desperate Celtic migrants attempting to force a crossing of the Rhone. A horde of 320,000 Helvetii and other Celtic tribes from Switzerland attempted to migrate into Gaul as the result of a domino effect of westward migrations caused by a Dacian invasion of Pannonia, and they burned their towns and villages before embarking on a death march. Caesar burned the only bridge across the Rhone and into Transalpine Gaul, and, when the Celts arrived at the river ford and asked for military access (promising not to attack), Caesar stalled them for fifteen days and built a fortified embankment and called in additional forces. Caesar ultimately declined their request, but small groups of people attempted to cross the river themselves during the night and day, desperate to escape the starvation of the barbarian horde and reach Gaul. They did not constitute a large army, but small family groups attempting to overwhelm the defenses or sneak by. However, the Romans concentrated missile fire and massacred them in the water, killing much of the frustrated mass of people as they tried to force their way. Ultimately, the Helvetii were forced to take an alternate route into Gaul, attacking Rome's allies in the process and giving Caesar an excuse to invade Gaul. The Battle of Bibracte saw the Helvetii massacred and forced to surrender, and, of the 368,000 Celts who began the migration (according to Greek-character tablets kept in the Helvetic camp), only 110,000 returned to the Helvetic lands (according to a census taken by Caesar). 200,000 of them were thus either slain in battle, died on the migration home, or settled in new lands along the way home.
Lack of trust[]
By the time of the Gallic Wars, Rome was only producing legionaries - heavy infantrymen armed with a throwing javelin, sword, and shield. The cavalry of Rome's legions was drawn from Rome's local allies, and, in the case of the Gallic Wars, they were drawn from Rome's Celtic vassals. However, Caesar grew suspicious about their dual loyalties, as, on one occasion, thousands of Gallic auxiliary cavalry fled in terror while fighting a few hundred Gallic rivals. In addition, during the Helvetic campaign, Caesar's allied tribes failed to provide food to his army during his pursuit of the Helvetii. When the allied Gallic leaders came to congratulate Caesar on his victory, praised his victory, and asked for his support against the Suebic king Ariovistus, he had all of their children taken hostage and tortured them if the Gallic kings went against his will. The Celtic kings, seeing an excuse, told Caesar that they had fifth columnists within their own tribes who wished to side with the Gallic patriots against Rome, as they had historic enemies among their own kind. Whenever the Celts failed to provide food to the Romans or failed to fight effectively, they used these seditious factions as an excuse for their own lack of loyalty.