Demetrius, worn down by his fruitless campaign, surrendered to Seleucus. At this point, he wrote to his son and to his commanders in Athens and Corinth telling them to henceforth consider him a dead man and to ignore any letters they might receive written under his seal. Macedonia, meanwhile, had been divided between Pyrrhus and Lysimachus, but, "like two wolves sharing a piece of meat", they soon fought over it with the result that Lysimachus drove Pyrrhus out and took over the whole kingdom. Following the capture of his father, Antigonus proved himself a dutiful son. He wrote to all the kings, especially Seleucus, offering to surrender all the territory he controlled and proposing himself as a hostage for his father's release, but to no avail. In 283 BC, at the age of 55, Demetrius died in captivity in Syria. When Antigonus heard that his father's remains were being brought to him, he put to sea with his entire fleet, met Seleucus's ships near the Cyclades, and took the relics to Corinth with great ceremony. After this, the remains were interred at the town of Demetrias that his father had founded in Thessaly. In 282 BC, Seleucus declared war on Lysimachus and the next year defeated and killed him at the Battle of Corupedium in Lydia. He then crossed to Europe to claim Thrace and Macedonia, but Ptolemy Keraunos, the son of Ptolemy, murdered Seleucus and seized the Macedonian throne. Antigonus decided the time was ripe to take back his father's kingdom, but when he marched north, Ptolemy Keraunos defeated his army. Ptolemy's success, however, was short-lived. In the winter of 279 BC, a great horde of Gauls under their leader Brennus descended on Macedonia from the north, crushed Ptolemy's army and killed him in battle, starting two years of complete anarchy in the kingdom. After plundering Macedonia, the Gauls invaded further regions of Greece, moving southwards. Antigonus cooperated in the defence of Greece against the barbarians, but the Aetolians took the lead in defeating the Gauls. In 278 BC a Greek army with a large Aetolian contingent checked the Gauls at Thermopylae and Delphi, inflicting heavy casualties and forcing them to retreat. The next year (277 BC), Antigonus sailed to the Hellespont, landing near Lysimachia at the neck of the Thracian Chersonese. When an army of Gauls under the command of Cerethrius appeared, Antigonus laid an ambush. He abandoned