Battle of Ipsus
Cassander associated himself with the Argead dynasty by marrying Alexander's half-sister, Thessalonica, and he had Alexander IV and Roxanne poisoned in either 310 BC or the following year. By 309 BC, Polyperchon began to claim that Heracles was the true heir to the Macedonian inheritance, at which point Cassander bribed him to have the boy killed. After this, Cassander's position in Greece and Macedonia was reasonably secure, and he proclaimed himself king in 305 BC. After the Battle of Ipsus in 301 BC, in which Antigonus was killed, he was undisputed in his control of Macedonia; however, he had little time to savour the fact, dying of dropsy in 297 BC.