279 BC and the once-dominant kingdom of Macedonia lies in ruins, ravaged by Brennus’ vast Celtic horde. Yet this horde’s leader was not satisfied with simply raiding Macedonia; eager for further fame and glory, Brennus now marches his army south, towards the richest, most prestigious Hellenic sanctuary of the time: Delphi.

Yet the Greeks had no intention of suffering a similar fate to their northern neighbours. Gathering a sizeable force, they march to confront Brennus at a place where numbers would count for little: Thermopylae.

Background: The Greek Cities, 279 BC

To the South of Macedonia lay the famed mainland Greek city-states of antiquity – poleis such as Athens, Sparta, Corinth and Thebes. In the past these cities had epitomised the zenith of strength and power in the Hellenic World. Yet by 279 BC, times had changed.

No longer were these Greek cities paragons of power and splendour. Now, they had become weak, isolated and war-weary. How this all came about can be traced back to events almost sixty years before, on the battlefield at a small town in Boeotia: Chaeronea.

338 BC: Macedonian hegemony

In 338 BC king Philip II, the ruler of Macedonia, made a decision that would shape the future of these cities for over a century. For twenty years, Philip had been strengthening his kingdom, transforming it from a realm on the brink of ruin into a world power. Now, he turned his attention south: to the famed Greek city-states of antiquity.

On the plains of Chaeronea, Philip and his new-look Macedonian army would gain a stunning victory against the Greek cities. In one crushing blow their open resistance to his rule was all but crushed and Philip asserted his authority over large swathes of the Greek mainland – lands he had won by the spear! Macedonian hegemony had arrived.

For the next 15 years the subdued city-states served Macedonian will as first Philip and then his famed son, Alexander, transformed their kingdom into the most powerful nation of the time. Yet Alexander’s unexpected death in Babylon, aged just 32, sent shockwaves through his empire. The reception of his death in the mainland Greek cities was no exception.

Many of these cities saw this as the opportune moment to rid themselves of their Macedonian overlords. Now was the time to strike and regain their liberty! Yet Alexander’s Macedonian successors – the Diadochi – had other ideas.

The Diadochi in Greece

The revolt erupted. Yet although initially successful, its result was never really in doubt. Within a year, the revolt was suppressed. The Macedonians were here to stay.

For the next forty years, Greece would become a pivotal theatre of war in the ensuing struggle that followed Alexander’s passing. Various Macedonian generals would wage bloody campaigns in the region – generals such as Polyperchon, Demetrius and Antigonus – each trying to curry favour with these weary city-states and gain supremacy. Once-dominant cities such as Athens and Corinth now became nothing greater than symbols of power for these Hellenistic warlords – pawns in the Macedonian Game of Thrones.

And so, by 279 BC, after sixty years of being in the shadows of their northern neighbours, the military power of many of these cities had never been so low. A fact that Brennus, the plunderer of Macedonia, was all-too aware of.

The fate of Macedonia

News now reached these Greek city-states of events in the North. Macedonia, the kingdom that for decades had reigned supreme, was in turmoil – the country pillaged, its people in despair and army vanquished. And more disturbing news would quickly follow: Desiring even more plunder, Brennus and his Celtic horde were marching south, leaving a trail of death and destruction in their wake. Greece was in jeopardy!

Once more, the famed Greek cities of old were under threat from an innumerous barbarian horde; once more the need for Hellenic unity against a northern menace became apparent. Yet creating this panhellenic defence would be no easy matter.

Distrust and rivalry was the common phenomenon between many of these cities by 279 BC. For some, the thought of serving alongside forces from another city would have been almost unbearable – how could they possibly serve alongside men who until only recently, they had seen as their bitterest enemies?

Panhellenism

The impending arrival of Brennus’ marauding horde provided these cities with the answer. Differences were temporarily cast aside and war preparations were made – their aim simple: defend the heartlands of Hellenism from the barbarians and survive!

Spearheading this PanHellenic effort were the Athenians. From Miltiades’ heroic charge at Marathon to the cunning of Themistocles off Salamis, the Athenians had a prestigious history of defending Hellas from vast barbarian armies. What city was better placed to be the epicentre of this new PanHellenic army?

Yet the Athenians knew that no matter how many Greeks answered the call, the great horde that was descending on their homeland would still dwarf their force in size. They thus sought a battlefield to counter this disadvantage – a place where numbers would count for little. And one place suited that style of warfare much greater than any other.

Thermopylae

Famed as the setting for the last stand of the 300 Spartans, the pass at Thermopylae had come to epitomise Greek defiance against overwhelming odds. Its narrow passage – blocked on one side by the mountains and the other by the sea – provided any defending army with two significant advantages. Not only did its limited space mean that they required only a small force to defend the pass, but it also rendered cavalry warfare almost useless: horsemen could neither efficiently charge nor flank their foe in such a restricted area.

For Callippus, the Athenian commander, this was ideal. Although his force did consist of a small contingent of formidable cavalry, most of the Greek army consisted of hoplites, heavily-armed infantrymen equipped with spear and shield. These men were ideal for close-combat fighting in defensive phalanx formations. Holding ground was their speciality.

The perfect defence

As for Brennus, Callippus knew fighting at Thermopylae would give his foe great difficulty. Its narrow passage meant the formidable size of his force would become more of a hindrance than a benefit, their weight of numbers forcing their front ranks into the deadly doru-points of the hoplite phalanx. Meanwhile the famed Celtic cavalry – some of the most formidable horsemen in antiquity – would be rendered next to useless.

The Athenians quickly reached a decision. Fighting at Thermopylae, they knew, was the best chance a united Greek force had at defeating the impending horde; here they might just pull off a miracle. At Thermopylae they would gather the PanHellenic army.

The army gathers

Hellenic forces from across the Aegean would not fail to answer the summons. Boeotians, Aetolians, Locrians, Phocians and Megarans – all would arrive at the pass with troops to aid the war-effort. And that was not all.

Ever hoping to improve their standing with the Greek cities, support from powerful Hellenistic warlords would also arrive to face the impending threat: from King Antiochus I, ruler of the supreme Seleucid Empire in Asia and from Antigonus Gonatas, the son of the famed Demetrius Poliorcetes. They had answered the call.

The defending force at Thermopylae soon swelled. In total, Callippus had over 25, 000 infantry, 2, 000 cavalry and a handful of ships under his command – no insignificant sum. Yet would it be enough to overcome the impending threat? Only time would tell.

Alarming news soon reached the Greek defence: Brennus and his Celtic horde were near. Already Thessaly had succumbed to the barbarian menace without a fight, its lands plundered and people in despair. And now, with the route to Boeotia more open than ever, Brennus was barely days away from reaching the Malian Gulf and Thermopylae. Time was running out.

Preparing the defences

Callippus and the Greeks were not unaware of how the last Greek defence at Thermopylae had been overcome. The famed mountain path across Mt Oeta – which had been used by Hydarnes and his Persian force all those years before – was common knowledge to them. If unguarded, this path, although difficult to traverse, could allow an army to both bypass and surround the defending force in the Hot Gates. The result would be a Greek slaughter.

Yet for the moment, Brennus and his approaching Celts were unaware of this one fatal flaw. Callippus prayed it would remain that way. But he would take no chances.

No doubt determined to avoid a repeat of the heroic Spartan last stand, Callippus ordered two of the Greek forces to prevent Brennus bypassing the main defence. The role of these two contingents would be critical.

The Greek flanks were now secure, with Brennus’ arrival being imminent. Yet the Greeks had one more card to play to complete their preparation.

The Sperchius

Hoping to hinder the enemy force before their arrival at the Pass, they dispatched their horsemen and lightly-armoured soldiers further north, to the southern bank of the Sperchius River. Their task was to guard the Sperchius, a river the Celtic horde had to pass over if they were to reach Thermopylae. Brennus would not cross without a fight!

The coming of the Celts

Brennus and his horde soon arrived at the River’s northern bank to an unwelcome site. Their path ahead was blocked: all the bridges had been destroyed, while lightly-armed Greeks were visible on the far-bank – taunting and ready to rain death on any Celtic attempts to cross the river.

Brennus knew that overcoming this barrier would be difficult. Any attempt to ford the river in daylight would inevitably prove very costly for his men: they would be sitting ducks in the water – target practice for the Greeks opposing them. This was what the Greeks had hoped Brennus would do. Yet Brennus had other ideas.

The night crossing

Waiting until darkness, Brennus selected 10, 000 of his soldiers – chosen for their height and swimming ability – and ordered them to an unknown crossing point near the mouth of the Sperchius. The Greeks, believing no such crossing existed, remained completely unaware.

Using their iconic oblong shields to help them, thousands of Celts floated silently across the Sperchius – no small military feat. The first layer of the Greek defence had been breached.

Roused from slumber to learn 10, 000 angry Celts were bearing down on them, the Greek vanguard hastily retreated to Thermopylae. It was either that or suffer a gruesome end. Taking full advantage, Brennus ordered the bridges to be rebuilt and duly crossed over with his army. The road to Thermopylae now lay open. First round to Brennus.

The Battle of Thermopylae 279 BC

Brennus wasted no time in advancing to the Hot Gates, arranging his army at the northern end of the Pass. Battle was imminent.

Leading his forces up the path in response, Callippus and the Greek army prepared to face the Celtic horde. Brennus’ warriors, eager for battle and encouraged by promises of unimaginable wealth that awaited them with victory, were all too happy to oblige. The forces collided. The Battle of Thermopylae had begun.

Death in the Pass

The fighting was fierce on either side. For a whole day the pass would be filled with the sounds of battle, each side desiring victory at all costs. The power of the Celtic warrior was formidable, each individual being a terrifying, deadly fighter. Yet brawn and ferocity is not the answer to everything in war.

In the narrow defile of Thermopylae, Greek discipline and cohesion quickly proved its worth. The solid Greek phalanx was in its element, as it was designed specifically with defence in mind. With the phalanx holding, Antigonus’ navy now also revealed its deadliness. Sailing next to the coastline, these ships rained a hail of arrows and various other missiles into the vulnerable flank of the Celtic army, dealing catastrophic damage and panic into the clustered enemy lines. The innumerable size of the Celtic horde, combined with their lack of armour, meant almost every arrow found a mark.

Celtic fury

Yet defiantly, the Celts pressed on, driven by a mad frenzy. Pausanias recalls,

They rushed at their adversaries like wild beasts, full of rage and temperament, with no kind of reasoning at all; they were chopped down with axes and swords but the blind fury never left them while there was breath in their bodies; even with arrows and javelins sticking through them they were carried on by sheer spirit while their life lasted. Some of them even pulled the spears they were hit by out of their wounds and threw them or stabbed with them.

(Pausanias 10. 21. 2)

By the end of the day, neither side had made a breakthrough; stalemate had been reached.

As the sun set, both sides retreated, the Greeks to the southern end of the pass and the Celts to their camp on the Sperchius plain. Callippus and the Greeks claimed victory; yet this was far from the truth. The battle was far from over.

Down but not out

Brennus’ army had suffered heavily in the attack. The discipline of the Greek phalanx combined with the deadly barrage from the Athenian navy and the light infantry had ensured Thermopylae had become a killing ground for the attacking horde. Yet the sheer size of the army – allegedly over 150, 000 strong – meant the Celtic force still vastly outnumbered their Greek foe.

Despite still having a significant numerical advantage, Brennus had no intention of recklessly attempting another frontal assault – an assault that would undoubtedly prove costly for his army.

He therefore now ordered his army to explore the nearby region, hoping to find a way around the Pass. Yet Callippus and the Greeks had prepared for this. As the Celts scouted the area, they encountered the Greek force at the Temple of Athena. Keen for plunder and booty, the horde soon descended on the Temple. Yet the small Greek garrison put up an almighty fight and they repelled the assault. The Celts were driven off Mount Oeta, back to the plain.

Having suffered another setback, the Celts were starting to lose heart. They had been repulsed in all their efforts; another devastating frontal assault on the Pass looked inevitable. Yet Brennus had no intention of needlessly sending his troops to slaughter. And so, the Prausian chief devised a brutal, yet effective plan.

Divide and conquer

Thanks to information he had acquired – most likely from Greek deserters – Brennus knew the size and strength of Callippus’ force occupying Thermopylae. He was to take full advantage of this.

Among the Greek force was a large contingent of soldiers from the Aetolian League, the most powerful state in Greece at that time. Nearly 8,000 Aetolian volunteers had arrived at the pass to aid the defence – almost a third of the entire Greek force! Their presence was no doubt critical to the defence. Brennus therefore devised a solution to rid himself of these opposing soldiers.

Selecting just over 40, 000 men for the task, Brennus ordered these warriors to march back across the Sperchius river and head west, towards Aetolia. Their mission was simple, but ruthless: they were to inflict as much death and destruction on an Aetolian town as possible and let the fear spread. The rumours of the havoc the Celts had created in Paeonia, Macedonia and Thessaly was about to become a stark reality for the Aetolians.

Under the command of two of Brennus’ commanders, Cambutis and Orestorius, these 40, 000 warriors set off on their ruthless mission. Very quickly, they carried it out with deadly efficiency at a town that would forever become remembered as the site of some of the most atrocious war crimes in antiquity.

Callion

Situated on the border of the region, Callion was the gateway to Aetolia from Thessaly. For the Celts, its location was thus ideal for their mission. It was the perfect place to send a message to the Aetolian force at Thermopylae; the perfect place from where they could threaten to unleash their full fury on the Aetolian heartlands.

What would happen next would be slaughter to an unbelievable extent. Men and women, the old and the young – none would be exempt from the atrocities inflicted by the Gauls. Pausanias recalls,

They butchered every human male of that entire race, the old men and the children at the breast… Any woman and mature virgins with a spark of pride killed themselves as soon as the city fell; those who lived were subjected with wanton violence to every form of outrage by men as remote from mercy as they were remote from love.

(Pausanias 10. 22. 2)

The Celts had been ruthless in carrying out their orders. Callion had been destroyed – its inhabitants slaughtered, houses plundered and sanctuaries set alight. It would send a devastating message.

Word spreads

News of the Callion atrocity soon reached Callippus’ army at Thermopylae – and most notably, the Aetolians. Aghast, these men feared the Celts would descend into their homeland; their cities, families and belongings now appeared under threat from suffering a similar fate to Callion. They could hardly stand idly by and let this happen.

Very quickly, the Aetolians at Thermopylae reached a decision. Desiring to defend their homeland, the 8, 000 men abandoned the Thermopylae defence and headed home in all haste. They likely feared it was already too late.

Yet unknown to them, these Celts had no intention of marching further into Aetolia. Having sacked Callion, they headed back towards Brennus’ main army and Thermopylae. Their mission was complete.

Brennus’ ruthless plan had succeeded spectacularly. With the departure of the Aetolians, Brennus now had a window where the Greek defence was considerably weakened. He made sure his army was ready to take full advantage.

The Mountain Pass

As Cambutis and Orestorius’ force laid waste to Callion, Brennus had not been idle. In the meantime, he had been sending more scouting parties into the region between the Sperchius and the Pass – this time avoiding what remained of the garrison at the Temple of Athena. Their aim had been simple: to find another route that would bypass the Hot Gates. Very quickly, their efforts paid dividends.

Brennus soon received reports from his scouts that they had discovered the famed mountain path of antiquity. If he could march his army along these passes, then Brennus knew he could bypass and surround the Greek defence entrenched at Thermopylae; the road to Delphi would lie open. This was his opportunity!

Yet Callippus had prepared for this possibility. The Phocian garrison he had placed defending the path remained strong, ready to give everything to protect their comrades. Would they be able to hold against the impending Celtic attack?

Gathering a sizable portion of his army, Brennus led these men towards the entrance of the mountain path near Heraclea. The rest of the army remained at Thermopylae, under the command of Brennus’ deputy, Achichorius, awaiting the given signal to strike. Everything depended on the success of Brennus’ manoeuvre.

The mist

At night, 40, 000 Celts advanced down the path in the footsteps of Hydarnes. Fearing for their lives if they did not oblige, Brennus had enlisted the help of local guides to aid him along the path. With their guidance, he and his Celtic force quickly made great progress, arriving at the Phocian defence in the early morning. More good fortune was to follow. As Brennus and his army approached, a great mist descended, obscuring their advance from the Phocian defenders. Seizing the initiative, Brennus wasted no time in ordering the attack, hoping to take his foe by complete surprise.

The result was devastating. Caught completely off-guard, defeat soon followed for the defending Phocians. Thanks to the mist, they never stood a chance.

Fighting bravely despite the hopelessness of the situation, some would manage to retreat to the pass, informing Callippus and their Greek comrades of their fate; many others however, would never leave the narrow defile, cut down by Brennus’ ferocious warriors. Brennus now had complete control of the pass. He ordered the advance; victory was near.

Reaching the end of the track and emerging behind the Greek defence, Brennus now ordered the main attack. Carnyx horns echoed through the pass, informing Achichorius and the main Celtic army that this was the moment they had been waiting for. The final assault had begun.

Evacuation

Unlike their Spartan predecessors, the Greeks were not resigned to suffer a similar fate of a heroic-but pointless last stand. They intended to survive!

Learning from the retreating Phocians that their defence had collapsed, Callippus had hastily ordered a desperate retreat. Thousands of Greek soldiers descended to the shoreline, scrambling to board Antigonus’ Athenian ships that were ready to evacuate them. Yet time was not on their side; both Brennus and Achichorius’ bloodthirsty warbands were closing in.

With their backs to the sea, a desperate struggle erupted between the Greek rearguard and the Celts, fighting all the way to the ships. Yet in the end, Callippus’ order to withdraw had come just in time. Thanks to heroic fighting from the Greek rear-guard, most of the army was evacuated. Truly this was the Dunkirk-equivalent of antiquity.

Yet although Callippus and his Greeks could perhaps take some comfort from this success, the reality was far bleaker. They had failed to defeat Brennus and his Celtic horde at the place best-suited to prevent the invasion. Nothing now prevented these barbarians from marching on the epicentre of Hellenic culture: Delphi. They needed a miracle.

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Notes and Further Reading

The cover image of this article is from the fantastic Ancient Warfare magazine, Volume III.4. This volume talks about ‘Implacable enemies: the Barcids at War’. Check it out here.

Huge thanks to Johnny Shumate and his fantastic illustrations!

Click here for Johnny’s website.

Johnny’s Etsy page, check it out here.

Information is from:

Pausanias’ account of the invasion of the Gauls (10.19.4-23.8) here.

Ellis, P. B. 1997, Celt and Greek: Celts in the Hellenic World, Constable.

Rankin, D. 1996, Celts and the Classical World. Routledge.

Author: Tristan Hughes Twitter Facebook

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