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.
A supply of iron quickly arrived from Athens, as well as stonemasons and whatever else was needed. Beginning then at the part of the fortification which they already held and building a cross-wall on the side of it facing Megara, from that point they built out on either side of Nisaea as far as the sea, the army apportioning among them the ditch and the walls and using stones and bricks from the suburbs. Moreover, they cut down fruit-trees and forest-wood and built stockades wherever they were needed; and the houses of the suburbs with the addition of battlements of themselves furnished a rampart.
They worked the whole of this first day, but on the next day toward evening when the wall was all but finished the garrison of Nisaea, becoming alarmed by the shortage of food, seeing that they received provisions from the upper-city for only a day at a time, and not anticipating any speedy relief from the Peloponnesians, and believing the Megarians to be hostile, capitulated to the Athenians on condition that they should give up their arms and pay a ransom of a stipulated amount for each man; as for the Lacedaemonians in the garrison, the commander or anyone else, they were to be disposed of as the Athenians might wish. On these terms they came to an agreement and marched out.
The Athenians then made a breach in the long walls in order to separate them from the wall of the city of Megara, took possession of Nisaea, and proceeded with their other preparations.
At this time Brasidas son of Tellis, a Lacedaemonian, happened to be in the neighbourhood of Sicyon and Corinth, preparing a force for use in the region of Thrace. And when he heard of the capture of the walls, fearing for the safety of the Peloponnesians in Nisaea and apprehensive lest Megara should be taken, he sent to the Boeotians requesting them to come in haste with an army and to meet him at Tripodiscus, which is the name of a village in the district of Megara at the foot of Mount Geraneia. He himself set out with two thousand seven hundred Corinthian hoplites, four hundred from Phlius, seven hundred from Sicyon, and such troops of his own as had already been levied, thinking that he would arrive before Nisaea had been taken.
But when he learned the truth—for he happened to have gone out by night to Tripodiscus—he selected three hundred of his own army, and before his approach was known reached the city of Megara unobserved by the Athenians, who were down by the sea. His plan was, ostensibly—and really, too, if it should prove possible—to make an attempt upon Nisaea, but most of all to get into the city of Megara and secure it. And he demanded that they should receive him, saying that he was in hopes of recovering Nisaea.
But the rival factions of Megara were afraid, the one that he might bring in the exiles and drive them out, the other that the populace, fearing this very thing, might attack them, and that the city, being at war with itself, while the Athenians were lying in wait near at hand, might be ruined. They, therefore, did not admit Brasidas, both parties thinking it best to wait and see what would happen.
For each party expected that there would be a battle between the Athenians and the relieving army, and so it was safer for them not to join the side which anyone favoured until it was victorious. So then Brasidas, when he could not persuade them, withdrew once more to his own army.
At daybreak the Boeotians arrived. They had intended, even before Brasidas summoned them, to go to the aid of Megara, feeling that the danger was not alien to them, and were already at Plataea with all their forces; but when the summons actually came, they were greatly strengthened in their purpose, and sent on two thousand two hundred hoplites and six hundred cavalry, returning home with the larger part of their army.