(M414) The reconquest of Ionia being completed, the satrap proceeded to organize the future government, the inhabitants now being composed of a great number of Persians. Meanwhile, Darius made preparations for the complete conquest of Greece. The wisdom of the advice of Miltiades, to destroy the bridge over the Danube, when Darius and his army would have been annihilated by the Scythians, was now apparent. Mardonius was sent with a large army into Ionia, who deposed the despots in the various cities, whom Artaphernes had reinstated, and left the people to govern themselves, subject to the Persian dominion and tribute. He did not remain long in Ionia, but passed with his fleet to the Hellespont, and joined his land forces. He transported his army to Europe, and began his march through Thrace. Thence marched into Macedonia, and subdued a part of its inhabitants. He then sent his fleet around Mount Athos, with a view of joining it with his army at the Gulf of Therma. But a storm overtook his fleet near Athos, and destroyed three hundred ships, and drowned twenty thousand men. This disaster compelled a retreat, and he recrossed the Hellespont with the shame of failure. He was employed no more by the Persian king. (M415) Darius, incited by the traitor Hippias, made new preparation for the invasion of Greece. He sent his heralds in every direction, demanding the customary token of submission—earth and water. Many of the continental cities sent in their submission, including the Thebans, Thessalians, and the island of Ægina, which was on bad terms with Athens. The heralds of Darius were put to death at Athens and Sparta, which can only be explained from the fiercest resentment and rage. These two powers made common cause, and armed all the other States over which they had influence, to resist the Persian domination. Hellas, headed by Sparta, now resolved to put forth all its energies, and embarked, in desperate hostility. A war which Sparta had been waging for several years against Argos crippled that ancient State, and she was no longer the leading power. The only rival which Sparta feared was weakened, and full scope was given, for the prosecution of the Persian war. Ægina, which had submitted to Darius, was visited by Cleomenes, king of Sparta, and hostages were sent to Athens for the neutrality of that island. Athens and Sparta suspended their political jealousies, and acted in concert to resist the common danger. (M416) By the spring of 490 B.C. the preparations of Darius were completed, and a vast army collected on a plain upon the Cilician shore. A fleet of six hundred ships convoyed it to the rendezvous at Samos. The exiled tyrant Hippias was present to guide the forces to the attack of Attica. The Mede Datis, and Artaphernes, son of the satrap of Sardis, nephew to Darius, were the Persian generals. They had orders from Darius to bring the inhabitants of Athens as slaves to his presence.