History of the Peloponnesian War

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.

Then, finally, when their whole army was at hand, consisting of not less than six thousand hoplites, and the Athenian hoplites were in line about Nisaea and the sea, while the lightarmed troops were scattered up and down the plain, the Boeotian cavalry fell upon the latter and drove them to the sea. The attack was unexpected, for hitherto no reinforcements had ever come to the Megarians from any quarter.