Xerxes fell into the trap laid for him, and modified his plans accordingly. For the successful accomplishment of the new Persian design three conditions were necessary:—the action must be prompt; it must be secret; the blocking of the eastern and western channels of Salamis strait must be carried out simultaneously. Even were there not more conclusive reasons for rejecting the time of the movement of the Persian fleet to the eastern strait as given by Herodotus, the fact that it would have conspicuously failed to fulfil the two most important of these evident conditions would render the accuracy of his statement a matter for serious consideration. But this does not afford any reason for rejecting Herodotus’ evidence as to the _nature_ of the movement. His description of it clearly identifies it with part of the movement which Æschylus and Diodorus attribute to the night preceding the battle. The identity is further confirmed by the fact that in all three historians no previous movement on the part of the Persian fleet at Phaleron is mentioned. ◆H. viii. 70.◆ Herodotus says that the Persian fleet, on being ordered to put out from Phaleron, sailed towards Salamis, and quietly took up its order in its various divisions. ◆Æsch Pers. 366, _ff_.◆ Æschylus says that Xerxes’ orders were that the fleet should put out after nightfall, and that “the close array of ships should be drawn up in three ranks to guard the exits of the straits and the roaring firths,” while others should circumnavigate the “Island of Ajax,” so as to close that line of retreat to the Greek fleet. Diodorus is practically in agreement with Æschylus in so far as the latter goes. ◆Diod xi. 17.◆ The king, he says, placed credence in the message which he had received, and hastened to prevent the naval forces of the Greeks from getting near the land army. He therefore immediately despatched the Egyptian contingent, ordering it to block the passage between Salamis and the Megarid.[161] ◆Cf. Plut. Them. 12.◆ The rest of the ships he sent towards Salamis, ordering them to attack the enemy, and decide the struggle by a naval battle. It is clear, then, that neither Æschylus nor Diodorus has any mention of a movement of the Persian fleet from Phaleron until after the receipt of Themistocles’ message; and Æschylus expressly states that the movement to the east end of the strait was made after the fall of night. ◆Plut. Them. 12.◆ As has been already pointed out, if it had been made during the daytime, the Greeks on board the fleet, among whom was Æschylus, could not have failed to know of it. Plutarch, though unreliable as an independent witness, is in agreement with Æschylus and Diodorus as to the Persian movement being subsequent to the receipt of Themistocles’ message.