The truth of this statement is demonstrated when we find a single fact referred to twice, as happens frequently in Thucydides' history: in one place as conclusion and elsewhere as prelude. Even the case of Nicias's letter offers evidence of this: that letter is mentioned right after the Athenian failure as the result of this failure ("Moreover, as he saw his own difficulties increase, day by day, along with the enemy forces, he too sent messengers rushing to Athens"). But after a chapter about Thrace, which makes a break and marks a change of episode, we move to Athens, to the beginning of winter, when that same letter arrived, and this time the text of the letter is given. It plays a new and primary role: it convinces the Athenians to send Demosthenes with reinforcements. As such, it becomes part of a different group, one in which, in a parallel manner, the different preparations made during the winter in each of the two camps are revealed. Clearly, from beginning to end of the two books, there is continuity: Alcibiades' speech leads to Gylippus's departure, Gylippus's success leads to Nicias's letter, and Nicias's letter leads to Demosthenes' departure. Yet this continuity is quite strongly marked by those narrative threads identified earlier; these make the continuity apparent despite clear junctions that interrupt the succession of events. The double role played, in this instance, by a single event is meant specifically to create bridges between these succeeding moments that accommodate the dual demand of unity and analysis.