For the part 1 see here: http://akrokorinthos.blogspot.com/2011/12/celts-and-greeks-acquaintance-of-two.html
The invasion of Macedon
|A fifteenth century French depiction of the death of Ptolemy Keraunos while fighting the Celts. Note how the artist has portrayed all the combatants as if they were contemporary French knights, right down to the plate armor.|
The collapse of the kingdom of Lysimachos(one of the successor states of Alexander's empire), the military weakness of the kingdom of Macedon after many wars against other successor kingdoms and the campaign of Pyrrhus' army to Italy(Pyrrhus and the Epirotes were the only allies who could provide assistance to Macedon) were favourable factors for a Gaulish invasion in Macedon. Thus during the winter of 280 BC three armies of Gauls followed by their families, invaded the Southern Balkans.The first army moved towards Thrace. The central army under the leadership of Brennos and Acichorius invaded Paionia. The western group under the leadership of Belgius invaded Dardania and later Macedonia.
The Macedonian king Ptolemaios Keraunos treated the ambassadors of the Celts with contempt. He underestimated the strength of the Gauls and attacked them with a small army that he had available as he had previously let the rest of his army spend the winter with their families. The battle resulted as a tragedy. The Macedonian army was annihilated and the king himself fell dead in the battlefield.
The road was now clear for the Gauls to loot Macedon. Luckily for the people of Macedon the Celts didn't have siege knowledge and they were all protected behind the walled cities.However the countryside was ravaged by the Celts.
Finally an old Macedonian general called Sosthenis achieved to make Belgios withdraw to the north.Although Belgios' army left Macedon Greece was not relieved from the Celts as the central army hearing about the riches of Macedon(probably from the withdrawing army) gave it a try and invaded Macedon too. Sosthenis once again took the responsibility to deal with the new invaders. He adopted skirmishing tactics which proved to be disastrous for the Gauls thus making them leave Macedon.
The invasion of Southern Greece
|The area where the Celts invaded in Greece. The Aetolian territories on the left. You can also see Thermopylae . Exactly south of Thermopylae was located the oracle of Delphi which was the primary target of Brennus.|
The central army of Gauls under Brennus and Antichorus instead of retreating towards the north as Belgius did, they moved towards southern Greece.The Thessalians reached an agreement with Brennus that they would let him pass through their land unless he wouldn't damage their farms and fields. The rest of the Greeks formed an alliance to confront this threat with the exception of the Peloponnesians who were feeling safe under the Corinth channel.
The Greek army was consisted of 30.000 of whom 11.000 were Aetolians ,10.500 were Thebans(Boeotians) ,3.500 were Phokeis ,1.500 were Athenians,700 were Lokrians and 400 Megareans.In addition Antiochus the Seleucid king and Antigonus Gonatas(grandchild of Antigonus the general of Alexander the Great) sent each 1.000 mercenaries in their efforts to assume the role of protector of Greece.
Although the Greek army was strong in numbers they were divided on the matter of leadership.The Aetolians and the Boeotians who had contributed the most(in numbers) in this army were debating over the leadership. Eventually a compromising solution was achieved by giving the leadership of the army to the Athenian general Kallippos.
Kallippos put the Greek army behind the river Spercheios thinking that the Celts wouldn't be able to cross the it because of the strong current.However the Celts found calm water and achieved to get across. The Greeks regrouped in Thermopylae.The Celts who numbered 40.000 men were not able to use the strength of their cavalry as the battlefield was so narrow. Their infantry attacks were all easily repelled.
Brennus cleverly sent a part of his army to invade Aetolia to force the Aetolians withdraw and weaken the Greek army.Brennus' plan was successful as the Aetolians left Thermopylae.Then he sent another contingent of his army through the mountains to hit the Greeks from the rear. This was exactly the same tactic that Xerxes used 200 years earlier against the 300 Spartans of Leonidas who held the narrow pass of Thermopylae.The Greek army was saved by the Athenian ships who transferred them to a safe ground.
In the same time the Aetolians achieved to repel the Gauls from Aetolia with the assistance of the Achaeans(north western Peloponesians). Brennus set as his target the Oracle of Delphi which was rumored to contain many riches. The oracle was a vulnerable target as it was defended only by 4.000 Aetolians ,Phokians and Magnites. Miraculously the defenders were able to stop the 40.000 strong Gaulish army. Both sides suffered heavy casualties. Brennus died either from serious injuries or because he commited suicide. The Gauls pursued by the Greek counter attacks suffering from the bad weather went to the north where they were divided again in two groups.The first one under Acichorius returned back to the Danube region and the second under Comodoris went eastwards towards Thrace.