(blocking the exit), they came round to a north–south alignment (see diagram). The Persian fleet seems to have been formed into three ranks of ships (according to Aeschylus); with the powerful Phoenician fleet on the right flank next to Mount Aigaleo, the Ionian contingent on the left flank and the other contingents in the centre. Diodorus says that the Egyptian fleet was sent to circumnavigate Salamis, and block the northern exit from the Straits. If Xerxes wanted to trap the Allies completely, this maneuver would have made sense (especially if he was not expecting the Allies to fight). However, Herodotus does not mention this (and possibly alludes to the Egyptian presence in the main battle), leading some modern historians to dismiss it; though again, others accept it as a possibility. Xerxes had also positioned around 400 troops on the island known as Psyttaleia, in the middle of the exit from the straits, in order to kill or capture any Greeks who ended up there (as a result of shipwreck or grounding). The opening phase Regardless of what time they entered the straits, the Persians did not move to attack the Allies until daylight. Since they were not planning to flee after all, the Allies would have been able to spend the night preparing for battle, and after a speech by Themistocles, the marines boarded and the ships made ready to sail. According to Herodotus, this was dawn, and as the Allies "were putting out to sea the barbarians immediately attacked them". If the Persians only entered the straits at dawn, then the Allies would have had the time to take up their station in a more orderly fashion. Aeschylus claims that as the Persians approached (possibly implying that they were not already in the Straits at dawn), they heard the Greeks singing their battle hymn (paean) before they saw the Allied fleet: Herodotus recounts that, according to the Athenians, as the battle began the Corinthians hoisted their sails and began sailing away from the battle, northwards up the straits. However, he also says that other Greeks denied this story. If this did in fact occur, one possible interpretation is that these ships had been a decoy sent to reconnoitre the northern exit from the straits, in case the arrival of the encircling Egyptian detachment was imminent (if indeed this also occurred). Another possibility (not exclusive of the former) is that