The Persians, hoping to gain an advantage from their superior numbers, now detached a squadron which was to coast along the eastern shores of Euboea, enter the strait at its southern end, and fall on the rear of the Greeks, while the main body attacked them in front. Eurybiades and Themistocles had early intelligence of this movement, but were not alarmed by it. Shortly before sunset the Greeks bore down on the Persians, attacked them in the narrow waters where their numbers could not tell, sank some thirty ships by ramming them, and then drew off as the night came on. It was a wild night. The Greeks had hardly regained their sheltered anchorage when the wind rose, lightning played round the mountain crests on either hand, the thunder rolled and the rain came down in torrents. The main Persian fleet, in a less sheltered position, found it difficult to avoid disaster, and the crews were horrified at seeing as the lightning lit up the sea masses of debris and swollen corpses of drowned men drifting amongst them as the currents brought the wreckage of the earlier storm floating down from beyond Cape Sepias. The hundred ships detached to round the south point of Euboea were still slowly making their way along its rocky eastern coast. Caught in the midnight storm most of them drove ashore and were dashed to pieces. In the morning the sea was still rough, but the Greeks came out of the strait, and, without committing themselves to a general action, fell upon the nearest ships, the squadron of Cilicia, and sank and captured several of them, retiring when the main fleet began to close upon them. On the third day the sea was calm and the Persians tried to force the narrows by a frontal attack. There was some hard fighting and loss on both sides, but the Greeks held their own. As the sun set the Persians rowed back towards their anchorage inside Cape Sepias. When the sun rose again the Greek fleet had disappeared. Eurybiades and Themistocles had agreed in the night after the battle that the time was come to abandon the defence of the Euboean Strait and retire to the waters of Salamis. The Persian army was now flooding the mainland with its myriads of fighting men, and was master of Attica. A fleet, depending so much on the land for supplies and for rest for its crews, could not maintain itself in the straits when the Persians held the mainland and were in a position to seize also the island of Euboea. Before sunrise the Greek ships were working their way in long procession through the Strait of Negropont. Early in the day they began to pass one by one the narrows at Chalcis, now spanned by a bridge. Then the strait widened, and there were none to bar their way to the open sea, and round Cape Sunium to their sheltered station in the straits behind the island of Salamis.