Rule of Macedon
As Antipater grew close to death in 319 BC, he transferred the regency of Macedon not to Cassander, but to Polyperchon, possibly so as not to alarm the other Diadochi through an apparent move towards dynastic ambition, but perhaps also because of Cassander's own ambitions. Cassander rejected his father's decision, and immediately went to seek the support of Antigonus, Ptolemy and Lysimachus as his allies. Waging war on Polyperchon, Cassander destroyed his fleet, put Athens under the control of Demetrius of Phaleron, and declared himself Regent in 317 BC. After Olympias’ successful move against Philip III later in the year, Cassander besieged her in Pydna. When the city fell in the spring of 316, Olympias was killed, and Cassander had Alexander IV and Roxana confined at Amphipolis.
That year, Cassander associated himself with the Argead dynasty by marrying Alexander's half-sister, Thessalonike, and overseeing the burial of Phillip III and Eurydice in the royal cemetery at Aegae; he further cemented his authority by founding Thessalonica, Cassandreia, and rebuilding Thebes. From 314 to 310, Cassander campaigned to the west and north, for a time extending Macedonian power as far as Apollonia and Epidamus, but was driven out by local rulers like Glaucius; his rule in Macedonia remained firm as he resettled defeated enemies in the tradition of Phillip II and fostered trade in the regions around his new cities. Cassander had Alexander IV and Roxana secretly poisoned in either 310 BC or the following year.
By 309 BC, Polyperchon had begun to claim that Heracles of Macedon was the true heir to the Macedonian inheritance, at which point Cassander bribed Polyperchon to kill the boy, promising him an alliance and the return of his Macedonian estates. After this, Cassander's position in Greece and Macedonia was reasonably secure, and he proclaimed himself king in 305 BC. Diodorus Siculus relates that Cassander, Ptolemy, and Lysimachus declared their kingships in response to the assumption of royal title by Antigonus, following his victory over Ptolemy at Salamis in 306.
In 307–304 BC he fought the so-called Four–Years' War against Athens. In 304 BC, his rival Antigonus Monophthalmus sent his son Demetrius Poliorcetes to aid Athens against Cassander. Demetrius succeeded in driving Cassander from central Greece and created a Hellenic League, the League of Corinth, against him. In the winter of 303–302 BC, Cassander opened negotiations with Antigonus with a view to establish peace, but Antigonus refused. At this Cassander turned to Lysimachus, Ptolemy, and Seleucus and convinced them to reform the coalition of 314–311 against Antigonus. In early 302 BC, Cassander sent one of his generals, Prepelaus, with an army from Macedon to join Lysimachus in an invasion of Antigonus's territory in Asia-Minor. Cassander himself marched with the main Macedonian field army into Thessaly to stop Demetrius from advancing into Macedon. Demetrius invaded Thessaly with a numerically superior force, Cassander stopped his advance by refusing to give battle and fortifying his positions. Lysimachus and Prepalaus had been very successful in Asia-Minor and Seleucus was marching with an army to join them. In the spring of 302 BC, Antigonus marched with an army from Syria into Asia-Minor to confront his enemies; he confronted Lysimachus and drove him from Phrygia. Antigonus realizing that the war would probably have to be decided in a major battle in Asia-Minor recalled Demetrius from Thessaly. With Demetrius gone Cassander sent part of his army with his brother, Pleistarchus, to join Prepalaus, Lysimachus and Seleucus in Asia-Minor. In 301 BC, the combined armies of Lysimachus, Seleucus, Prepalaus and Pleistarchus faced the combined armies of Antigonus and Demetrius at Ipsus. After the Battle of Ipsus in which Antigonus was killed, Cassander was undisputed in his control of Macedon; however, he had little time to savour the fact, dying of dropsy in 297 BC.
Cassander's dynasty did not live much beyond his death, with his son Philip dying of natural causes, and his other sons Alexander and Antipater becoming involved in a destructive dynastic struggle along with their mother. When Alexander was ousted as joint king by his brother, Demetrius I took up Alexander's appeal for aid and ousted Antipater, killed Alexander V and established the Antigonid dynasty. The remaining Antipatrids, such as Antipater II Etesias, were unable to re-establish the Antipatrids on the throne.
