Cassander was born in about 350 BCE; he was the son of Antipater, the viceroy of Alexander the Great in Macedonia. It is likely that Cassander remained in Europe during Alexander's campaign, but in 324 BCE, his father sent him as a messenger to the king in Asia. Cassander must have been at the royal court in Babylon when Alexander died in June 323 and was succeeded by Arrhidaeus, who was mentally deficient and needed a regent. Cassander's whereabouts during the next three years remain unclear.
In the late summer of 320, at the Conference of Triparadisus, he was appointed chiliarch.note[Diodorus, World History 18.48.4.] When his father died in the autumn of 319, he was confirmed in this office.
Second Diadoch War
However, he had been dreaming of being the official regent of king Arrhidaeus; instead, an officer named Polyperchon occupied the regency. Cassander revolted in 317 and was accepted as regent by queen Eurydice. Arrhidaeus and Olympias, the queen-mother, were both killed before the year was over.note[Diodorus, World History 19.11.]
These events took place during the Second Diadoch War (318-316), in which the champions of the royal family of the Argeads, Polyperchon and Eumenes, fought against Cassander and Antigonus Monophthalmus, who presented themselves as supreme commanders of the Macedonian forces in Europe and Asia. Now that the official king was dead, the fights came to an end.
Cassander now tried to expand his power to Greece and permitted the Thebans to rebuild their city (316), which had been destroyed by Alexander. Cassander also invaded the land of the Taulanti, an Illyrian tribe, which he subdued. He added the Greek towns of Apollonia and Epidamnus to his realm, essentially creating a land route from the Aegean Sea to the Adriatic Sea.
Two new cities in Macedonia were founded: Potideia was refounded as Cassandria, while Therma was refounded as Thessaloniki. This name was derived from queen Thessalonike, daughter of Philip, sister of Alexander, wife of Cassander. Another new city was Ouranopolis ("heavenly city"), a private project of Cassander’s brother Alexarchus, who was nicknamed “the sun”.
Third Diadoch War
The peaceful period came to an end when Cassander, Ptolemy Soter (ruler in Egypt), and Lysimachus (ruler in Thrace) started to believe that Antigonus became too powerful. In 314, the Third Diadoch War broke out. To gain influence in Cassander's Greek backyard, Antigonus declared the Freedom of the Greek city States (text).
The war was to last until 311. The peace treaty confirmed Ptolemy and Lysimachus in their territories; Cassander and Antigonus Monophthalmus remained supreme commanders of the Macedonian forces in Europe and Asia; the Greek towns were recognized by all parties as "free and autonomous" (although Cassander would keep garrisons at several places); and it was agreed that the boy king Alexander IV, son of Alexander the Great and his wife Roxane, would become sole ruler of the entire empire when he came of age, in 305.note[Diodorus, World History 19.105.]
The result was, as could be expected, that the royals were killed as soon as possible. This was the end of the Argead dynasty. Cassander's reputation never recovered: he would always be blamed for the murder of Arrhidaeus, Olympias, Alexander IV, and Roxane.
Fourth Diadoch War
The Fourth Diadoch War broke out in 307. Antigonus' son Demetrius Poliorcetes attacked Cassander in Europe and created a Greek League, directed against the man in Macedonia, but in the end, Antigonus and Demetrius were defeated by Cassander, Lysimachus, and their ally Seleucus (Battle of Ipsus, 301). In the meantime, the Successors of Alexander had accepted the royal title.note[Plutarch, Life of Demetrius 18.2.]
In 298, Cassander died. Unlike the other Diadochi, he did not create a dynasty; he was succeeded by Demetrius Poliorcetes of the House of Antigonus.