The History of the Grecian War (1.1.1-1.1.3)

Thucydides, an Athenian, wrote the war of the Peloponnesians and the Athenians as they warred against each other, beginning to write as soon as the war was on foot, with expectation it should prove a great one and most worthy the relation of all that had been before it; conjecturing so much both from this, that they flourished on both sides in all manner of provision, and also because he saw the rest of Greece siding with the one or the other faction, some then presently and some intending so to do.

For this was certainly the greatest commotion that ever happened among the Grecians, reaching also to part of the barbarians and, as a man may say, to most nations.

For the actions that preceded this and those again that are yet more ancient, though the truth of them through length of time cannot by any means clearly be discovered, yet for any argument that, looking into times far past, I have yet light on to persuade me, I do not think they have been very great, either for matter of war or otherwise.