17. Even if we descend to the consideration of such trivial matters as hunting, the case is still the same; for he will be most successful in the chase who is acquainted with the size and nature of the wood, and one familiar with the locality will be the most competent to superintend an encampment, an ambush, or a march. But it is in great undertakings that the truth shines out in all its brilliancy, for here, while the success resulting from knowledge is grand, the consequences of ignorance are disastrous. The fleet of Agamemnon, for instance, ravaging Mysia, as if it had been the Trojan territory, was compelled to a shameful retreat. Likewise the Persians and Libyans,[59] supposing certain straits to be impassable, were very near falling into great perils, and have left behind them memorials of their ignorance; the former a monument to Salganeus on the Euripus, near Chalcis, whom the Persians slew, for, as they thought, falsely conducting their fleet from the Gulf of Malea[60] to the Euripus; and the latter to the memory of Pelorus, who was executed on a like occasion. At the time of the expedition of Xerxes, the coasts of Greece were covered with wrecks, and the emigrations from Æolia and Ionia furnish numerous instances of the same calamity. On the other hand, matters have come to a prosperous termination, when judiciously directed by a knowledge of the locality. Thus it was at the pass of Thermopylæ that Ephialtes is reported to have pointed out to the Persians a pathway over the mountains, and so placed the band of Leonidas at their mercy, and opened to the Barbarians a passage into Pylæ. But passing over ancient occurrences, we think that the late expeditions of the Romans against the Parthians furnish an excellent example, where, as in those against the Germans and Kelts, the Barbarians, taking advantage of their situation, [carried on the war] in marshes, woods, and pathless deserts, deceiving the ignorant enemy as to the position of different places, and concealing the roads, and the means of obtaining food and necessaries.