History of the Peloponnesian War

The rest of the army were mercenaries, hired by Brasidas out of Peloponnesus. [But] Brasidas himself the Lacedaemonians sent out, chiefly because it was his own desire;

notwithstanding the Chalcideans also longed to have him, as one esteemed also in Sparta every way an active man. And when he was out, he did the Lacedaemonians very great service.

For by showing himself at that present just and moderate towards the cities, he caused the most of them to revolt; and some of them he also took by treason. Whereby it came to pass that if the Lacedaemonians pleased to come to composition (as also they did), they might have towns to render and receive reciprocally. And also long after, after the Sicilian war, the virtue and wisdom which Brasidas showed now, to some known by experience, by others believed upon from report, was the principal cause that made the Athenian confederates affect the Lacedaemonians.

For being the first that went out, and esteemed in all points for a worthy man, he left behind him an assured hope that the rest also were like him.

Being now come into Thrace, the Athenians upon notice thereof declared Perdiccas an enemy, as imputing to him this expedition, and reinforced the garrisons in the parts thereabouts.

Perdiccas with Brasidas and his army, together with his own forces, marched presently against Arrhibaeus, the son of Bromerus, king of the Lyncesteans, a people of Macedonia, confining on Perdiccas his dominion, both for a quarrel they had against him and also as desiring to subdue him.