Herodotus’ statements as to the greatness of the objects of this expedition of Mardonios would not of themselves be convincing did not its magnitude, when compared with the expedition of 490, imply that its aims were infinitely more ambitious. The fleet which took part in the earlier expedition seems to have been at least as large as that of two years later; and, in addition to the fleet, Mardonios had, as has been said, a very large land army, for he had brought down with him a considerable number of troops over and above those already in West Asia which the suppression of the revolt would render largely available. The punishment of Athens and Eretria was an essential part of the programme of this expedition; but it was only a part. The dictates of policy would render it advisable for Darius to show the European Greeks that they could not with impunity interfere in the affairs of Asia. But the expedition was not, like that of 490, limited in its scope to Athens and Eretria. It threatened Greece as a whole. The results of Mardonios’ campaign were that Macedonia and Thrace (the southern part of it) were re-conquered, and remained passive in the hands of Persia for thirteen succeeding years. Thasos was also annexed. Herodotus’ estimate of its result is coloured by the failure of the design in so far as Greece was concerned; but, on his own showing, the campaign was a success in so far as the operations in Macedonia and Southern Thrace were concerned. Darius, now definitely prepared to carry out his schemes against the liberty of European Greece, was in no way diverted from them by the disaster off Mount Athos. He only altered his plan of action. #STRATEGY OF 492 AND 490.# Alike on the north and east of the Ægean, circumstances had been in 492, for the first time in Persian history, favourable for the prosecution of his plans west of that sea. The events of the past twenty years had only served to emphasize some of the more important considerations which must have been present in his mind when the plan was originally formed. He knew, he must have known, that, unless he were prepared to adopt the dangerous policy of entrusting the commanders in the West with a large permanent force, the recurrence of a rising on the part of the ever-restless Greek might be looked for so long as the liberty of his brethren across the sea contrasted with his own servitude in Asia. He greatly under-estimated the difficulties of the conquest of European Greece; but that he regarded it as a serious undertaking is shown by the magnitude of the expedition which was despatched to Europe under Mardonios. The strategic plan of that campaign was similar to that adopted in the expedition of 480. The disaster off Athos modified his design. It showed him the dangers attendant upon the voyage of a large fleet by that circuitous route in those stormy seas,—a voyage which would be protracted by the necessity of keeping touch with the slow advance of the army on land.