After the Greek defeat at Battle of Thermopylae, the Gauls retreated out of Greece and moved through Thrace and finally into Asia.
Antigonus' father, Demetrius Poliorcetes, had been driven from the Macedonian throne by Pyrrhus of Epirus and Lysimachus in 288 BC.
Tired of war, Demetrius surrendered himself to Seleucus I Nicator in 285 BC, leaving Antigonus as the Antigonid heir to the Macedonian throne.
The Gauls looted the camp, but when they started to attack the ships, Antigonus's army appeared, trapping them with the sea to their rear.
It was around this time, under these favorable omens, that his son and successor, Demetrius II Aetolicus was born by his niece-wife Phila.