=Second Persian War.=--The second war began ten years later with an invasion. Xerxes united all the peoples of the empire, so that the land force amounted, as some say, to 1,700,000 men.[75] There were Medes and Persians clad in sleeved tunics, armed with cuirasses of iron, bucklers, bows and arrows; Assyrians with cuirass of linen, armed with clubs pointed with iron; Indians clad in cotton with bows and arrows of bamboo; savages of Ethiopia with leopard skins for clothing; nomads armed only with lassos; Phrygians armed with short pikes; Lydians equipped like Greeks; Thracians carrying javelins and daggers. The enumeration of these fills twenty chapters in Herodotus.[76] These warriors brought with them a crowd equally numerous of non-combatants, of servants, slaves, women, together with a mass of mules, horses, camels, and baggage wagons. This horde crossed the Hellespont by a bridge of boats in the spring of 480. For seven days and nights it defiled under the lash. Then traversing Thrace, it marched on Greece, conquering the peoples whom it met. The Persian fleet, 1,200 galleys strong, coasted the shores of Thrace, passing through the canal at Mount Athos which Xerxes had had built for this very purpose. The Greeks, terrified, submitted for the most part to the Great King and joined their armies to the Persian force. The Athenians sent to consult the oracle of Delphi, but received only the reply; "Athens will be destroyed from base to summit." The god being asked to give a more favorable response, replied, "Zeus accords to Pallas [protectress of Athens] a wall of wood which alone shall not be taken; in that shall you and your children find safety." The priests of whom they asked the interpretation of this oracle bade the Athenians quit Attica and go to establish themselves elsewhere. But Themistocles explained the "wall of wood" as meaning the ships; they should retire to the fleet and fight the Persians on sea. Athens and Sparta, having decided on resistance, endeavored to form a league of the Greeks against the Persians. Few cities had the courage to enter it, and these placed themselves under the command of the Spartans. Four battles in one year settled the war. At Thermopylæ, Leonidas, king of Sparta, who tried to bar the entrance to a defile was outflanked and overwhelmed. At Salamis, the Persian fleet, crowded into a narrow space where the ships embarrassed one another, was defeated by the Greek navy (480). At Platæa the rest of the Persian army left in Greece was annihilated by the Greek hoplites; of 300,000 men but 40,000 escaped. The same day at Mycale, on the coast of Asia, an army of the Greeks landed and routed the Persians (479). The Greeks had conquered the Great King.