[15][16] Although not mentioned in ancient historiography, Sirras was possibly the Illyrian chieftain during the Peloponnesian War taking the side of Athens, as an ally of the Lynkestian king Arrhabaeus against Perdiccas II of Macedon.
[17][18] At first Sparta avoided involvement in Macedon's war with Arrhabaeus, but in 423 BC they joined an expedition which ended with a retreat by the Macedonians and a brilliantly contrived escape of the Spartans.
[21] Thucydides reports Brasidas saying that the Illyrians may terrify those with an active imagination, they are formidable in their outward bulk, their loud yelling is unbearable and the brandishing of their weapons in the air has a threatening appearance, but when it comes to real fighting with an opponent who stands his ground they are not what they seemed; they have no regular order that would make them ashamed of deserting their positions when hard pressed; with them flight and attack are equally honourable, and afford no test of courage; their independent mode of fighting never leaving anyone who wants to run away without a fair excuse of doing so.
Perdiccas was interested in peace with Lynkestis due to his recent defeat in the Lynkestian campaign, the Illyrian-Lynkestian collaboration, and his new enmity with Brasidas.
[24] In 413 Perdiccas's son Archelaus obtained the throne of Macedon, and he evidently continued his father's conflict against the Lynkestians, probably involving Illyrians.
[25] Additionally, Archelaus made general ameliorations to the military and reinforced the borders of his kingdom,[26] which apparently held the Illyrians momentarily at bay.