Epipolae, and began constructing lines intended to extend from shore to shore, while their ships blockaded the harbour. For a brief space all seemed going well; the Syracusans were frequently repulsed in sallies against these lines (though Lamachus was killed in one of them); and in their despair they deposed their generals, Hermocrates and his colleagues, and began treating with Nicias for a surrender. The rapid reversal of these fair prospects is one of the most dramatic incidents in military history, and may be directly traced to Alcibiades. It was by his advice that the Spartans resolved upon taking an active part in a war, which in itself did not concern them or justify a breach of the fifty years' peace. That justification was, however, easily found in a plundering expedition on the part of the Athenians on the coast of Laconia. Gylippus was despatched from Sparta with a small force and arrived at Tarentum when the fortunes of the Athenians seemed at their highest point. He might even now have been intercepted, but Nicias regarded the smallness of his force with contempt, and made no effort to prevent his sailing through the straits. He therefore coasted along the northern shore of Sicily and landed at Himera. Here he collected large numbers both of Greeks and native Sicels and marched to Syracuse, penetrating the Athenian lines at a point where they were incomplete and weakly guarded. His arrival turned the scale completely. A cross-wall was built which for ever prevented the completion of the circumvallation by the besiegers, and Nicias for
