If Darius had ever entertained doubts as to the necessity for occupying European Greece to ensure the preservation of peace in her Asiatic sister-country, the revolt of Ionia must have completely dissipated them.  It was a question whether the cities which had so obstinately defied him for six long years, would ever resign themselves to servitude as long as they saw the peoples of their race maintaining their independence on the opposite shores of the AEgean, and while the misdeeds of which the contingents of Eretria and Athens had been guilty during the rebellion remained unpunished.  A tradition, which sprang up soon after the event, related that on hearing of the burning of Sardes, Darius had bent his bow and let fly an arrow towards the sky, praying Zeus to avenge him on the Athenians:  and at the same time he had commanded one of his slaves to repeat three times a day before him, at every meal, “Sire, remember the Athenians!"*

* The legend is clearly older than the time of Herodotus, for in the Persae of Eschylus the shade of Darius, when coming out of his tomb, cries to the old men, “Remember Athens and Greece!”

As a matter of fact, the intermeddling of these strangers between the sovereign and his subjects was at once a serious insult to the Achaemenids and a cause of anxiety to the empire; to leave it unpunished would have been an avowal of weakness or timidity, which would not fail to be quickly punished in Syria, Egypt, Babylon, and on the Scythian frontiers, and would ere long give rise to similar acts of revolt and interference.  Darius, therefore, resumed his projects, but with greater activity than before, and with a resolute purpose to make a final reckoning with the Greeks, whatever it might cost him.  The influence of his nephew Mardonius at first inclined him to adopt the overland route, and he sent him into Thrace with a force of men and a fleet of galleys sufficient to overcome all obstacles.  Mardonius marched against the Greek colonies and native tribes which had throw off the yoke during the Ionian war, and reduced those who had still managed to preserve their independence.  The Bryges opposed him with such determination, that summer was drawing to its close before he was able to continue his march.  He succeeded, however, in laying hands on Macedonia, and obliged its king, Alexander, to submit to the conditions accepted by his father Amyntas; but at this juncture half of his fleet was destroyed by a tempest in the vicinity of Mount Athos, and the disaster, which took place just as winter was approaching, caused him to suspend his operations (492).  He was recalled on account of his failure, and the command was transferred to Datis the Mede and to the Persian Artaphernes.  Darius, however, while tentatively using the land routes through Greece for his expeditions, had left no stone unturned to secure for himself that much-coveted sea-way which would carry him straight into the heart of the