Book VI of Thucydides deals, through its speeches in particular, with Athenian motivation towards sending the great expedition to Sicily, with the attitudes of various factions involved, and with the seeds of the expedition's ultimate disastrous conclusion. It contains memorable sections on Alcibiades, on the Athenians' excitement at the sailing, on the mutilation of the Herms and a digression on the fall of Athenian tyranny a century earlier. This edition, with introduction and notes, is designed to help senior school and university students read, understand and enjoy Thycydides. Its notes aim to assist translation, draw attention to features of language and style characteristic of the author, make explicit what the author took for granted in his original Greek audience, comment on the historical background, and offer grounds on which to reach decisions as to whether the author's historical statements are true or false.