Of these the first seems to have been but half accomplished; and though more success had been attained with the second, the failure to fully accomplish the first made it impossible for Darius to avail himself for the time being of the advantages won along that western route. He had found the Thracians, as others found them in later days, a much more difficult conquest than he had in all probability anticipated.
It is now possible to consider whether the attempt to arrive at an ethnic frontier is the only object which may be suggested as guiding the policy with regard to Thrace. Despite the obscurity of the evidence, it seems clear that Darius intended the conquest of Thrace to be a prelude to further conquest westwards, and that, in pursuance of this design, European Greece was to be the next object of attack. Whether the conquest of Greece was to be merely a second stage in a great scheme of conquest along the northern shores of the Mediterranean, or whether it was merely designed for the purpose of securing the western borders of the empire by subjugating the free kinsmen of the most western subjects of the empire, cannot now be said, inasmuch as there is no evidence which throws light upon the question.
It now remains to consider the evidence,—
(1) As to Darius’ design of conquest westward;
(2) As to the reasons why the attempts to carry it out was postponed for many years.
The operations of Megabazos on the Strymon, followed by the demand for the submission of Macedonia, are certainly strong indications, if not conclusive evidence of, the design to get hold of the coast route to Northern Greece.
For the carrying out of operations on the scale requisite for an expedition aiming at the reduction of Greece as a whole, the command of a land route was necessary. The carrying capacity of a ship of those days was so small that it would have been very difficult, if not impossible, to transport a force of the magnitude required across the Ægean. The expedition of 490 represents in all probability the utmost that Persia could accomplish by sea transport, and that was merely directed against Athens and Eretria, and had as its declared object the punishment of the only two states of European Greece which had interfered in the Ionian revolt.
But the results of Megabazos’ campaign, if unsupported by other facts, would afford very inadequate evidence of a design on Greece.
H. iii. 138.
There is, however, a tale in Herodotus, the very telling of which by that historian argues strongly for its general truth. It is the story of Demokedes, the famous physician of Kroton, who, having been in the service of Polykrates of Samos, was captured by the Persians at the time of his murder, and after a series of adventures became court physician at Susa. PERSIANS EXPLORE THE GREEK COAST. About the time when Darius was starting for the Scythian expedition, this Demokedes had rendered a great service to Atossa, the wife of Darius, who, instructed by him, persuaded Darius to send him with an expedition to explore the coasts of Greece, with a view to the subsequent invasion of the country. H. iii. 136. Accompanied by some prominent Persians, Demokedes went down to Sidon in Phœnicia, where the expedition embarked on two triremes and set sail for Greece. They circumnavigated the land, keeping close to the shore, surveying the coasts, and making notes thereof in writing. “At length, having examined the greatest part of it, they proceeded to Tarentum in Italy.” What happened thereafter is not so important. Suffice it to say that, with the aid of the tyrant of Tarentum, Demokedes made his escape, and went to Kroton, whither the Persians followed. The Krotonians refused to surrender him. The Persians accordingly sailed back to Asia, but, “not having their guide, they did not attempt to explore Greece any further.” It is not necessary to recount the rest of their adventures. H. iii. 129–138. Herodotus closes the tale by remarking that they were the first Persians who came from Asia to Greece, and that they were spies.