History of the Peloponnesian War
Thucydides
Thucydides, Vol. 1-4. Smith, Charles Foster, translator. London and Cambridge, MA: Heinemann and Harvard University Press, 1919-1923.
but Gortynia, Atalanta, and some other places capitulated voluntarily out of friendship for Amyntas son of Philip, who accompanied Sitalces; moreover they laid siege to Europus, but were unable to take it. Next they advanced into the other part of Macedonia, which is to the west of Pella and Cyrrhus.
Beyond these places, however, into Bottiaea and Pieria, they did not penetrate, but ravaged Mygdonia, Grestonia, and Anthemus. The Macedonians, on the other hand, did not even think of defending themselves with infantry, but calling upon their allies in the interior for additional cavalry, though few against many, they dashed in among the Thracian army wherever they chose.
And wherever they charged no one could withstand them, for they were good horsemen and protected by cuirasses; but since they were constantly being hemmed in by superior numbers and found themselves imperilled by the horde that was many times their own number, they finally desisted, thinking that they were not strong enough to fight with the larger force.
Sitalces now began to hold parleys with Perdiccas about the matters for which he had undertaken the expedition; and since the Athenians (who did not believe that Sitalces would come, though they sent gifts and envoys to him) had not arrived with their promised fleet, he despatched part of his army into the territory of the Chalcidians and Bottiaeans, and shutting them up within their walls ravaged their lands.
But while he was staying in the neighbourhood of these places, the peoples which dwell to the south—the Thessalians, the Magnesians and other subjects of the Thessalians, and the Hellenes as far south as Thermopylaebecame frightened lest the host should come against them also, and so were making preparations.
The same alarm was felt also by the Thracians who inhabit the plain beyond the Strymon to the north, that is, the Panaeans, Odomantians, Droans, and Dersaeans, independent tribes.