Antigonus III Doson Antigonus III Doson ( ) was king of Macedon from 229 BC to 221 BC . He was a member of the Antigonid dynasty . Family Background . Antigonus III Doson was a half - cousin of his predecessor , Demetrius II Aetolicus . Doson ' s father was Demetrius the Fair ( briefly king of Cyrene ) , the son of Demetrius Poliorcetes and his third wife , Ptolemaïs , daughter of Ptolemy I Soter and Eurydice , daughter of Antipater . As such , Demetrius the Fair was , on his father ' s side , a younger half - brother of Demetrius II ' s father , Antigonus II Gonatas , the son of Poliorcetes by his first wife , Phila , another of Antipater ' s daughters ; as well as a nephew of both Ptolemy Keraunos and Meleager on his mother ' s side . According to Eusebius , Doson ' s own mother was a Thessalian noblewoman , Olympias , daughter of Pauliclitus of Larissa . Antigonus also had a brother named Echecrates , whose son , named Antigonus after Doson himself , was put to death by Perseus on the latter ' s accession to the throne of Macedon . Doson ' s father , Demetrius the Fair , died sometime around 250 BC , as a result of events that occurred after being summoned from Macedonia to Cyrene to marry Berenice II , the daughter and heir of Magas of Cyrene . Rather than contenting himself with his young bride , Demetrius openly became the lover of her powerful mother , Apama II . So the jealous bride took her revenge by having him assassinated . It is unclear whether Doson ' s mother had died before this time . The meaning of Antigonus ' by - name is uncertain . According to Plutarch it " implied that he was given to promising but did not perform his engagements " , though even the exact meaning of this is unclear . Regent of Macedonia . When Demetrius II died in battle in 229 BC , his son and would - be successor , the later Philip V , was only nine years old . According to Plutarch , both the Macedonian army and nobility thought the political situation too volatile to wait for Philip V to mature enough to assume command . As a consequence , the Macedonian nobility turned to Doson , who was subsequently made regent of the kingdom and married to his predecessor ' s widow and the mother of Philip , Chryseis . However , it was only after Doson demonstrated his leadership abilities by succeeding ( where his cousin Demetrius had failed ) in defeating the Dardanii invaders and also in putting down a rebellion by the Thessalians , and showing his rule to be generally moderate and good , that he given the title of king . Unlike his Antigonid ancestors , he had no viable rivals to challenge his right to rule . Yet , even as king he apparently envisioned himself as caretaker for his cousin ' s son , Philip V . King of Macedonia . As king , Antigonus III proved to be as much a master of tactical diplomacy as of military strategy . In less than a decade of rule he not only secured the borders of his nation , he also reestablished Macedon as the dominant power in the region . Unlike previous Macedonian rulers who attempted direct dominion over their fiercely independent neighbors to the West and South , he formed alliances with Epirus and the Achaean League . When Sparta , under Cleomenes III , attempted to establish hegemony over the whole Peloponnese , Aratus of Sicyon - long the leader of Greek opposition to Macedonian domination - invited Antigonus to intervene ( 226 BC ) . Establishing his base on the heights above Corinth , Antigonus reconstituted a broad - based Hellenic league ( 224 BC ) under his leadership before launching his attack on Sparta . The Spartan forces , outmatched by the larger , better equipped Macedonian army , were so overwhelmed in the battle of Sellasia ( 222 BC ) that Cleomenes only managed to escape with a few horsemen , and ultimately had to seek refuge in Egypt . However , in a magnanimous gesture , Antigonus restrained his soldiers from plundering Sparta , saying it was Cleomenes , not Sparta , that was his enemy . Antigonus did not long survive this victory . For , while his forces were campaigning in the southern Peloponnese , Illyrians invaded Macedonia from the north . Antigonus had to rush north to repel this new threat . On his way , Antigonus passed through Tegea and Argos , his arrival at the latter coinciding with the beginning of the Nemean Games , where he was honoured by the Achaean League and various other cities . His death occurred soon after , when he returned to Macedon and engaged the Illyian army ; for though Macedonian forces were once again victorious , the commander became sick during the battle ( possibly though not necessarily as a result of a ruptured blood vessel ) and died .