That insane expedition across the Danube into Scythia comes now to be recounted. It was undertaken by Darius for the purpose of avenging the inroad and devastation of the Scythians in Media and Upper Asia, about a century before. The lust of conquest imparted unusual force to this sentiment of wounded dignity, which in the case of the Scythians could hardly be connected with any expectation of plunder or profit. In spite of the dissuading admonition of his brother Artabanus,[480] Darius summoned the whole force of his empire, army and navy, to the Thracian Bosphorus,—a force not less than seven hundred thousand horse and foot, and six hundred ships, according to Herodotus. On these prodigious numbers we can lay no stress. But it appears that the names of all the various nations composing the host were inscribed on two pillars, erected by order of Darius on the European side of the Bosphorus, and afterwards seen by Herodotus himself in the city of Byzantium,—the inscriptions were bilingual, in Assyrian characters as well as Greek. The Samian architect Mandroklês had been directed to throw a bridge of boats across the Bosphorus, about half-way between Byzantium and the mouth of the Euxine. So peremptory were the Persian kings that their orders for military service should be punctually obeyed, and so impatient were they of the idea of exemptions, that when a Persian father named Œobazus entreated that one of his three sons, all included in the conscription, might be left at home, Darius replied that all three of them should be left at home,—an answer which the unsuspecting father heard with delight. They were indeed all left at home,—for they were all put to death.[481] A proceeding similar to this is ascribed afterwards to Xerxês;[482] whether true or not as matters of fact, both tales illustrate the wrathful displeasure with which the Persian kings were known to receive such petitions for exemption.