It is quite possible, then, that some report of disaster did lead to the formation of a plot in which all the tyrants were more or less implicated, but which for some unknown reason never came to a head. If it had been a one-man plot, in which Miltiades had played a solo part, surely his design must have become known to Darius. #ORIGIN OF THE LEGEND.# And yet on return to Asia Darius passed through Miltiades’ dominions, the only part, apparently, of the Hellespontine region to which the infection of rebellion had not spread. If Miltiades had taken part in the plot, and if any judgment can be formed from the general practice of Persian kings, it can hardly be supposed that he would have lived to fight at Marathon. It now remains to consider briefly how the extraordinary story of the march beyond the Ister can possibly have originated. Doubtless the Greeks in the cities on the north coast had many a tale brought to them by the native traders from the interior of the commotion caused by the sudden appearance of this strange army within the Scythian borders. These tales, probably wild exaggerations even in their original form, would not, it may be certain, lose aught in the course of their evolution. An element common to all of them would be that somewhere in the Hinterland this army had appeared; and it may well be that within a comparatively short period the most easterly of the Greek cities came to regard their own Hinterland as the scene of its operations. This would bring the imaginary march of the army to the neighbourhood of the Don and the Volga. In actual fact, however, it is impossible to suppose that the most extreme point ever reached by Darius was far north of the Ister. It is in the highest degree improbable that he ever passed the well-defined boundaries set by the Carpathians and the Pruth. With regard to the motives of the expedition, Herodotus declares that it was intended as a retaliation for the Scythian invasion of Western Asia, which spread desolation through part of the continent, and was about synchronous with, and largely the cause of, the fall of the Assyrian Empire. Apart from the improbability of Darius cherishing resentment for occurrences of such ancient date, or for injuries of which he was in no real sense heir, he was probably aware, though Herodotus was not, that the people who lived to the north of the Euxine were wholly distinct from the Sakæ, whom Herodotus calls Scyths, who had troubled the continent more than a century before this time. The unreliability and vagueness of the story of the campaign have led to the formation in modern times of many conjectures as to the object with which it was undertaken.