It is, however, evident that the main part of the material for the history of the campaign up to the point where this apology begins, is taken from a version emanating from an “aristocratic” source—that is to say, from that party which was most bitterly opposed to Pericles at the time at which Herodotus wrote. It has already been pointed out that the Persian expedition of 490 was organized on a less ambitious scale than that of 492, and that it must consequently be concluded that its objects were less ambitious. How far Herodotus was able in later days to obtain authentic information from the Persian side with regard to the end which Darius had in view, it is impossible to say; but there is a remarkable accord between one of his statements of the Persian motives and his actual narrative of facts. This feature of his account would not be so striking, were it not conspicuously absent from other important parts of his history. The motives of the expedition seem to have been twofold— (1) A declared motive,—the punishment of Athens and Eretria. (2) A motive which the Persian had good reason for keeping, in so far as possible, in the background,—the establishment of a _tête-du-pont_ on the European shore in Attica. The first of these is expressly stated by Herodotus. Of the existence of the second he appears to have had an inkling. ◆H. vi. 94.◆ He says that the expedition was due to Darius’ desire for revenge, and to the charges and importunities of the Peisistratidæ. He further says that Darius wished “on this pretext” (_i.e._ the representations made by the Peisistratidæ) “to subdue those people in Greece which had not given earth and water.” From an historical point of view, exception must be taken to one phase of this last statement; in fact, in other words in the same chapter Herodotus narrows it down to a noticeable extent. He omits all mention of the recalcitrant states, and says that Darius appointed Datis and Artaphernes to the command “with orders to enslave Athens and Eretria, and to bring the slaves into his presence.” The facts with regard to the expedition make it evident that Darius was anxious to limit, in so far as possible, the declared scope of it. It did not aim at a large measure of conquest in Greece. The contrast in point of numbers between it and the expedition of Mardonios has been already referred to. The Persian war policy of this age is characterized by one invariable feature—a large numerical margin relative to the end to be attained. Darius’ recent experiences in Ionia were not likely to make him grossly underestimate the forces requisite for any large design of conquest in Greece. If this be recognized, certain features of the Persian policy at this particular time become explicable. Let it be assumed that ◆H. vi. 49.◆ Herodotus’ statement as to the wide nature of the demand for “earth and water” is correct.[59]