History of the Peloponnesian War

For they thought they might do it boldly, falsely estimating the power of the Athenians to be less than afterwards it appeared, and making a judgment of it according to [blind] wilfulness rather than safe forecast; it being the fashion of men, what they wish to be true to admit even upon an ungrounded hope, and what they wish not, with a magistral kind of arguing to reject.

Withal, because the Athenians had lately received a blow from the Boeotians, and because Brasidas had said (not as was the truth, but as served best to allure them) that when he was at Nisaea the Athenians durst not fight with those forces of his alone, they grew confident thereon, and believed not that any man would come against them.

But the greatest cause of all was that for the delight they took at this time to innovate, and for that they were to make trial of the Lacedaemonians, not till now angry, they were content by any means to put it to the hazard. Which being perceived, the Athenians sent garrison soldiers into those cities, as many as the shortness of the time and the season of winter would permit. And Brasidas sent unto Lacedaemon to demand greater forces, and in the meantime prepared to build galleys on the river Strymon.