Polygamy was used by Macedonian kings both before and after Amyntas to secure marriage alliances and produce enough heirs to offset losses from intra-dynastic conflict.

He claims that Eurynoe prevented her mother and her lover (unnamed, but likely Ptolemy of Aloros) from assassinating Amyntas late in his reign by revealing the plan to her father.

[2][8] According to Justin, Amyntas spared Eurydice because they shared children, but that she would later help murder Alexander and Perdiccas in order to place Ptolemy on the throne.

[9] Alexander was in fact killed by friends of Ptolemy at a festival in 368 BC, but the extent to which Eurydice knew of or participated in this plot is opaque.

[15] Amyntas also adopted the Athenian general Iphicrates around 386 BC in recognition of his military services and marital ties with the Thracian king, Cotys I.

[21] As Diodorus tells us, the younger Amyntas seized the throne at this point in 393/2 BC after assassinating the previous king Pausanias.

To shore up his country against the threat of the Illyrians, Amyntas established an alliance with the Chalcidian League led by Olynthus.

In exchange for this support, Amyntas granted them rights to Macedonian timber, which was sent back to Athens to help fortify their fleet.

That Olynthus was backed by Athens and Thebes, rivals to Sparta for the control of Greece, provided them with an additional incentive to break up this growing power in the north.