Antiochus, the son of Seleucus Callinicus, and the sixth from the founder of his dynasty, surnamed by his contemporaries the Great, was perhaps eminent in energy and ability above most of his line, though certainly not comparable in this respect to his ancestor, the Conqueror. He seems to have owed that title, – which however imported little in an age so lavish of such distinctions, that his grandfather, a vile and odious prince, was surnamed the God – chiefly to the contrast between the low state into which the Syrian monarchy had fallen when he ascended the throne, and that to which he finally raised it, but especially to his expedition for the recovery of the eastern provinces which had been taken from it by the Parthian and Bactrian kings, an expedition which by its extent, duration, and dazzling success, might to a degenerate race recal the achievements of the Macedonian conqueror. He seems to have been elated with the sounding epithet, and to have forgotten how largely he was indebted for his triumphs to the imbecility of his Egyptian neighbours; and in an evil hour he conceived the project of enlarging the hounds of his empire until it should include all the conquests made by the first Seleucus after his victory over Lysimachus.

By the event of the battle of Ipsus the allies, who had been united by their common enmity to Antigonus, were transformed into jealous rivals. Their struggle with him was no sooner decided, than the clashing interests of Ptolemy and Seleucus threatened an immediate rupture, which was averted indeed, but so as to leave neither party secure, and one of them deeply offended. It was clear that the possession of Syria must be a subject of perpetual contest between the two states. On the other hand, Lysimachus had reason to be satisfied–if it was in the nature of ambition to be so – with the rich acquisition which had fallen to his share: but he could feel no confidence in the moderation of his powerful neighbour, and might well suspect that Seleucus would endeavour to resume so important a concession on the first opportunity. In the eyes both of Lysimachus and Ptolemy, Seleucus had stept into the place of Antigonus; and they soon gave public proof of the jealousy with which they regarded him, by a new alliance which they contracted with one another. Lysimachus, although he had so lately married Amastris, and had children by a former wife, an Odrysian princess – among whom the eldest Agathocles was a youth of great promise – received the hand of Arsinoe, Ptolemy's daughter by Berenice.

After the termination of the Cleomenic War Greece enjoyed a short interval of general tranquillity. The states which had taken a part in the recent contest needed repose; and the Achæans, though they were now rid of their formidable antagonist, were not the more at liberty to engage in any fresh enterprises without the consent of the master to whose dominion they had been subjected by the selfish and short-sighted policy of Aratus. Throughout Peloponnesus military preparations and martial exercises were suspended: the people returned to the occupations of peace: the Megalopolitans began to settle again amidst the ruins of their city.

The death of Antigonus produced no immediate visible change in the state of affairs; but yet it may be considered as the main cause of the movements which ensued, and which soon after involved Greece in another wasteful and calamitous war. The occasion of this new struggle arose indeed at a great distance from Macedonia, without any intervention of the Macedonian government, and seemingly more through accident than design; yet it could hardly have taken place, and certainly would not have been attended with such consequences, if the restraint hitherto imposed on those who were desirous of change by the ability and success of Antigonus, had not been withdrawn.

The appearance of Antigonus with an army before Argos implies a series of events, which are scarcely noticed by any of the authors who have preserved fragments of the history of this period. Pausanias says the most, when he mentions that, while Pyrrhus was occupied with the invasion of Greece, Antigonus recovered the Macedonian cities. Pyrrhus, as we have seen, had given some offence to the national feelings, and even without such an occasion, it would not have been surprising that a revolution should have taken place during his absence. But the recovery of places in Macedonia cannot have been the first or chief object that engaged the attention of Antigonus. For the present all he wanted was an army to enable him to meet his rival in Greece, and in this period nothing was easier than to raise one. There were every where military adventurers ready to flock to any standard which held out a prospect of prey or plunder. It is probable that, as soon as he had collected a sufficient force, he began his march, reserving the settlement of Macedonia for his future leisure. After the fall of Pyrrhus, the greater part of his army, which was chiefly composed of Macedonians, seems to have passed into the service of Antigonus.

Greece was now permitted to enjoy another short interval of repose, while Philip returned to Macedonia, where his presence was needed to protect his north-west frontier against the inroads of Scerdilaidas. He was fully occupied in this quarter during the rest of the summer of 217, and in the ensuing winter he increased his navy with 200 new galleys built on the Illyrian model. In the spring he embarked his forces, and sailed round Peloponnesus into the Adriatic. Though Italy was uppermost in his thoughts, so as to haunt his dreams, he thought it necessary, before he crossed the channel, to secure his dominions more effectually against Scerdilaidas, and for this purpose resolved to make an expedition to the coast of Illyria. He expected, it seems, that the Romans would send succours to Scerdilaidas, as in fact the Illyrian, when he heard of Philip's maritime preparations, had requested them to do; and he therefore waited for some time between Cephallenia and Leucas, to ascertain the movements of the Roman fleet. But having learnt that it was still at Lilybæum, he sailed up toward Apollonia, and had anchored near the mouth of the Aous, when he received advice that Roman galleys had been seen at Rhegium bound for Apollonia. Believing that the whole Roman fleet was at hand, he gave immediate orders for retreat, and, as if chased by a victorious enemy, pushed forward day and night until he reached Cephallenia.