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.
And they arrived on the coast of Thrace on the fortieth day after the revolt of Potidaea.
The news of the revolt of the cities quickly reached the Athenians also; and when they learned that troops under Aristeus were also on the way to support the rebels, they sent against the places in revolt two thousand of their own hoplites and forty ships, under Callias son of Calliades with four other generals.
These first came to Macedonia and found that the former thousand had just taken Therme and were besieging Pydna;
so they also took part in the siege of Pydna. But afterwards they concluded an agreement and an alliance with Perdiccas, being forced thereto by the situation of Potidaea and tie arrival of Aristeus, which compelled them to hasten, and then they withdrew from Macedonia.
On their way they came to Beroea and thence to Strepsa,[*](In Mygdonia, north of Therme.) and after an unsuccessful attempt upon this place proceeded overland to Potidaea with three thousand hoplites of their own and with many of their allies besides, and with six hundred Macedonian cavalry, who were under the command of Philip and Pausanias; and at the same time their ships, seventy in number, sailed along the coast.
And marching leisurely they arrived on the third day at Gigonus, and went into camp.
The Potidaeans and the Peloponnesians under Aristeus were awaiting the Athenians, encamped on the Olynthian side of the isthmus; and they had established a market outside of the city.
The allies had chosen Aristeus general of all the infantry, and Perdiccas of the cavalry; for Perdiccas had immediately deserted the Athenians again[*](For his first desertion of the Athenians, see Thuc. 1.57.) and was now in alliance with the Potidaeans, having appointed Iolaus as his administrator at home.
The plan of Aristeus was as follows: he was to hold his own army on the isthmus and watch for the approach of the Athenians, while the Chalcidians and the other allies from outside of the isthmus[*](i.e. the Bottiaeans, who, like the Chalcidians, lived outside the isthmus.) and the two hundred horse furnished by Perdiccas were to remain at Olynthus; then when the Athenians should move against the forces of Aristeus, the others were to come up and attack them in the rear, and thus place the enemy between their two divisions.