Ptolemy Keraunos
In 282 BC, Seleucus declared war on Lysimachus and the next year defeated and killed him at the Battle of Corupedium in Lydia. He then crossed to Europe to claim Thrace and Macedonia, but Ptolemy Keraunos, the son of Ptolemy, murdered Seleucus and seized the Macedonian throne. Antigonus decided the time was ripe to take back his father's kingdom, but when he marched north, Ptolemy Keraunos defeated his army.