With the fall of Thermopyae and the contact established between his army and his fleet, Xerxes found his route open for the invasion of Attica. Since there was no possibility of opposing him on land, the population of the province was removed and Athens left to its fate. Themistocles, who was in command of the Athenian division of the Greek fleet, now urged the assembling of the fleet at Salamis, partly to cover the withdrawal of the Athenians and partly to assist in the defense of the Isthmus of Corinth, which was to be the next stand of the Greeks. The advice was adopted and the fleet assembled off the town of Salamis. Athenian refugees had crowded into the town and from the heights above they watched the smoke of their burning city. Their own future and the future of Athenian civilization hung on the long lines of triremes drawn up on the shore. A glance at the map of the region of Salamis shows the advantages offered by the position for the defensive. The fighting off Artemisium had shown the peril of attacking a greatly superior force in the open because of the danger of being outflanked. In the narrow straits between Salamis and the mainland the Greek line of battle would rest its flanks on the opposite shores. But it is one thing to choose a position and another to get the enemy to accept battle in that position. If the Persians ignored the Greek fleet and moved to the Isthmus, the Greeks would be caught in an awkward predicament. To regain touch with the Greek army, the fleet would be then compelled to come out of the straits and fight at a disadvantage in the open. There was only one chance of defeating the Persian fleet and that was to make it fight in the narrow waters of the strait where numbers would not count so heavily. Everything depended on bringing this to pass. Nor could the Greeks wait indefinitely for the Persians. Already the incorrigible jealousies of rival cities had almost reached the point of disintegrating the fleet. Although the commander in chief was the Spartan general Eurybiades, the whole Spartan contingent was on the point of deserting in a body to its own coasts. The situation was saved by Themistocles. Having wrung from his allies a reluctant consent to stop at Salamis temporarily to cover the withdrawal of the Athenian populace, the story is that he secretly dispatched a messenger to Xerxes to say that if he would attack at once he could crush the entire naval forces of the Greeks at a blow, but if he delayed the Greeks would scatter. Acting on this advice, Xerxes landed troops on the island of Psyttaleia, dispatched a squadron to block the western outlet of Salamis Straits, and proceeded to move the main body of his fleet to attack the Greeks by way of the eastern channel. The preparations were made during the night and were not completed till dawn of the day of battle, September 20, 480 B.C.