The power of Antigonus in Asia underwent a material diminution, by the successful and permanent establishment which Seleucus now acquired in Babylonia; from which event the era of the succeeding Seleucidæ takes its origin. In Greece, however, Antigonus gained ground on Cassander. He sent thither his nephew Ptolemy with a large force to liberate the Greeks, or in other words, to expel the Cassandrian garrisons; while he at the same time distracted Cassander’s attention by threatening to cross the Hellespont and invade Macedonia. This Ptolemy (not the Egyptian) expelled the soldiers of Cassander from Eubœa, Bœotia, and Phocis; having taken Chalcis, Oropus, Eretria, and Carystus, he entered Attica and presented himself before Athens. So much disposition to treat with him was manifested in the city, that Demetrius the Phalerean was obliged to gain time by pretending to open negotiations with Antigonus, while Ptolemy withdrew from Attica. Nearly at the same epoch, Apollonia, Epidamnus, and Leucas, found means, assisted by an armament from Corcyra, to drive out Cassander’s garrisons, and to escape from his dominion. The affairs of Antigonus were now prospering in Greece, but they were much thrown back by the discontent and treachery of his admiral Telesphorus, who seized Elis and even plundered the sacred treasures of Olympia. Ptolemy presently put him down, and restored these treasures to the god.
[312-308 B.C.]
In the ensuing year, a convention was concluded between Antigonus, on one side, and Cassander, Ptolemy (the Egyptian) and Lysimachus, on the other, whereby the supreme command in Macedonia was guaranteed to Cassander, until the maturity of Alexander son of Roxane; Thrace being at the same time assured to Lysimachus, Egypt to Ptolemy, and the whole of Asia to Antigonus. It was at the same time covenanted by all, that the Hellenic cities should be free. Towards the execution of this last clause, however, nothing was actually done. Nor does it appear that the treaty had any other effect, except to inspire Cassander with increased jealousy about Roxane and her child; both of whom (as has been already stated) he caused to be secretly assassinated soon afterwards, by the governor Glaucias, in the fortress of Amphipolis, where they had been confined. The forces of Antigonus, under his general Ptolemy, still remained in Greece. But this general presently (310 B.C.) revolted from Antigonus, and placed them in co-operation with Cassander; while Ptolemy of Egypt, accusing Antigonus of having contravened the treaty by garrisoning various Grecian cities, renewed the war and the triple alliance against him.
Polysperchon—who had hitherto maintained a local dominion over various parts of Peloponnesus, with a military force distributed in Messene and other towns—was now encouraged by Antigonus to espouse the cause of Heracles (son of Alexander by Barsine), and to place him on the throne of Macedonia in opposition to Cassander. This young prince Heracles now seventeen years of age, was sent to Greece from Pergamus in Asia, and his pretensions to the throne were assisted not only by a considerable party in Macedonia itself, but also by the Ætolians. Polysperchon invaded Macedonia, with favourable prospects of establishing the young prince; yet he thought it advantageous to accept treacherous propositions from Cassander, who offered to him partnership in the sovereignty of Macedonia, with an independent army and dominion in Peloponnesus. Polysperchon, tempted by these offers, assassinated the young prince Heracles, and withdrew his army towards Peloponnesus. But he found such unexpected opposition, in his march through Bœotia, from Bœotians and Peloponnesians, that he was forced to take up his winter quarters in Locris (309 B.C.). From this time forward, as far as we can make out, he commanded in southern Greece as subordinate ally or partner of Cassander.
The assassination of Heracles was speedily followed by that of Cleopatra, sister of Alexander the Great, and daughter of Philip and Olympias. She had been for some time at Sardis, nominally at liberty, yet under watch by the governor, who received his orders from Antigonus; she was now preparing to quit that place, for the purpose of joining Ptolemy in Egypt, and of becoming his wife. She had been invoked as auxiliary, or courted in marriage, by several of the great Macedonian chiefs, without any result. Now, however, Antigonus, afraid of the influence which her name might throw into the scale of his rival Ptolemy, caused her to be secretly murdered as she was preparing for her departure; throwing the blame of the deed on some of her women, whom he punished with death.
All the relatives of Alexander the Great (except Thessalonice wife of Cassander, daughter of Philip by a Thessalian mistress) thus successively perished, and all by the orders of one or other among his principal officers. The imperial family, with the prestige of its name thus came to an end.