DARIUS (521-485 B.C.).--For a short time, a pretender, a Magian, who called himself _Smerdis_, and professed to be the brother of Cambyses, usurped the throne. Cambyses is said to have put an end to his own life. After a reign of seven months, during which he kept himself for the most part hidden from view, Smerdis was destroyed by a rising of the leading Persian families. Darius, the son of Hystaspes, of the royal race of the _Achaemenidae_, succeeded. He married _Atossa_, the daughter of Cyrus. The countries which composed an Oriental empire were so loosely held together that the death of a despot or the change of a dynasty was very likely to call forth a general insurrection. Darius showed his military prowess in conquering anew various countries, including Babylon, which had revolted. He made Arabia tributary, and spread the bounds of his vast empire as far as India and in North Africa. A mighty expedition which he organized against the Scythians on the Lower Danube failed of the results that were hoped from it. The barbarians wasted their own fields, filled up their wells, drove off their cattle, and fled as the army of Darius advanced. He returned, however, with the bulk of his army intact, although with a loss of prestige, and enrolled "the Scyths beyond the sea" among the subjects of his empire. His armies conquered the tribes of _Thrace_, so that he pushed his boundaries to the frontiers of Macedonia. The rebellion of the Greek cities on the Asia-Minor coast he suppressed, and harshly avenged. Of his further conflicts with the Greeks on the mainland, more is to be said hereafter. He had built _Persepolis_, but his principal seat of government appears to have been _Susa_. He did a great work in organizing his imperial system. The division into _satrapies_--large districts, each under a _satrap_, or viceroy--was a part of this work. He thus introduced a more efficient and methodical administration into his empire,--an empire four times as large as the empire of Assyria, which it had swallowed up.