The Persians immediately determined to resort to the measures which Themistocles had recommended to prevent the escape of any part of the Greek fleet. There was a small island between Salamis and the coast of Attica, that is, on the eastern side of Salamis, called Psyttalia, which was in such a position as to command, in a great measure, the channel of water between Salamis and the main land on this side. The Persians sent forward a detachment of galleys to take possession of this island in the night. By this means they hoped to prevent the escape of any part of the Greek squadron in that direction. Besides, they foresaw that in the approaching battle the principal scene of the conflict must be in that vicinity, and that, consequently, the island would become the great resort of the disabled ships and the wounded men, since they would naturally seek refuge on the nearest land. To preoccupy this ground, therefore, seemed an important step. It would enable them, when the terrible conflict should come on, to drive back any wretched refugees who might attempt to escape from destruction by seeking the shore. By taking possession of this island, and stationing galleys in the vicinity of it, all which was done secretly in the night, the Persians cut off all possibility of escape for the Greeks in that direction. At the same time, they sent another considerable detachment of their fleet to the westward, which was the direction toward the isthmus, ordering the galleys thus sent to station themselves in such a manner as to prevent any portion of the Greek fleet from going round the island of Salamis, and making their escape through the northwestern channel. By this means the Greek fleet was environed on every side--hemmed in, though they were not aware of it, in such a way as to defeat any attempt which any division might make to retire from the scene. The first intelligence which the Greeks received of their being thus surrounded was from an Athenian general named Aristides, who came one night from the island of AEgina to the Greek fleet, making his way with great difficulty through the lines of Persian galleys. Aristides had been, in the political conflicts which had taken place in former years at Athens, Themistocles's great rival and enemy. He had been defeated in the contests which had taken place, and had been banished from Athens. He now, however, made his way through the enemy's lines, incurring, in doing it, extreme difficulty and danger, in order to inform his countrymen of their peril, and to assist, if possible, in saving them.