=50.= Meanwhile the Greeks had not been idle. The ten years since the battle of Marathon had been employed in active drilling of forces, by sea and land. Each state furnished its quota; and though but a handful compared with the myriads of invaders, they had the strength, derived from patriotism and high discipline, to oppose the mere material mass and weight of the Persian host. It was mind against matter. [Sidenote: B. C. 480.] =51.= Abandoning the defense of Thessaly, which was open by too many avenues to the Persians, the little army of Leon´idas, king of Sparta, had made a resolute stand at Thermopylæ, a narrow pass between Mount Œta and the sea. The whole force amounted to only 6,000 men, of whom but 300 were Spartans. Xerxes waited several days upon the Trachinian plain, expecting that this little band would melt away from mere terror at the sight of his vast numbers. At length he sent the Median cavalry to force a passage. They were repulsed with loss. The Immortals made the same attempt with no better success. At this point, Ephial´tes, a Malian, offered for a large reward to show the invaders a mountain-path by which they could reach the rear of the Spartan camp. The Phocian guards of this path were overpowered. Leonidas learned that he was betrayed, and declaring that he and his Spartans must remain at their post, dismissed all the rest of his army except the Thespians and Thebans. Then, before the body of Persians who were crossing the mountain, under lead of the traitor, could attack him from behind, he threw himself upon the enemy in front, resolving to exact as dear a vengeance as possible. Many of the Persian host fell beneath the Spartan swords, many were trodden to death by their own multitudes, and many were forced into the sea. Leonidas soon fell, and the contest for his body inspired his men with new fury. Having recovered it, they placed their backs against a wall of stone and fought until every man was slain. =52.= During the same days several battles were fought at sea between the Greek and Persian fleets. No decisive advantage was gained by either side, but the result was most disheartening to the Persians, who had been most confident of success. The elements, too, had neither been scourged nor scolded into good behavior; a terrible hurricane raged three days and nights upon the coast of Thessaly, tearing the ships from their moorings and dashing them against the cliffs. At least four hundred ships of war were thus destroyed, beside a countless number of transports with their stores and treasures. Another squadron of two hundred vessels, which had been sent around Eubœa to cut off the retreat of the Greeks, perished, in a sudden tempest, upon the rocks. The Grecian commanders were unable to profit by these advantages, for the defeat at Thermopylæ compelled them to withdraw from Artemis´ium to provide for the safety of Attica and the Peloponnesus.