(Κυαξάρας), was, according to Herodotus, the third king of Media, the son of Phraortes, and the grandson of Deioces. He was the most warlike of the Median kings, and introduced great military reforms, by arranging his subjects into proper divisions of spearmen and archers and cavalry. He succeeded his father, Phraortes, who was defeated and killed while besieging the Assyrian capital, Ninus (Nineveh), in B. C. 634. He collected all the forces of his empire to avenge his father's death, defeated the Assyrians in battle, and laid siege to Ninus. But while he was before the city, a large body of Scythians invaded the northern parts of Media, and Cyaxares marched to meet them, was defeated, and became subject to the Scythians, who held the dominion of all Asia (or, as Herodotus elsewhere says, more correctly, of Upper Asia) for twenty-eight years (B. C. 634-607), during which time they plundered the Medes without mercy. At length Cyaxares and the Medes massacred the greater number of the Scythians, having first made them intoxicated, and the Median dominion was restored. There is a considerable difficulty in reconciling this account with that which Herodotus elsewhere gives (1.73, 74), of the war between Cyaxares and Alyattes, king of Lydia. This war was provoked by Alyattes having sheltered some Scythians, who had fled to him after having killed one of the sons of Cyaxares, and served him up to his father as a Thyestean banquet. The war lasted five years, and was put an end to in the sixth year, in consequence of the terror inspired by a solar eclipse, which happened just when the Lydian and Median armies had joined battle, and which Thales had predicted. This eclipse is placed by some writers as high as B. C. 625, by others as low as 585. But of all the eclipses between these two dates, several are absolutely excluded by circumstances of time, place, and extent, and on the whole it seems most probable that the eclipse intended was that of September 30, B. C. 610. (Baily, in the Philosophical Transactions for 1811; Oltmann in the Schrift. der Brel. Acad. 1812-13; Hales, Analysis of Chronology, i. pp. 74-78; Ideler, Handbuch der Chronologie, i. p. 209, &c.; Fischer, Griechische Zeilttafeln, s. a. 610.) This date, however, involves the difficulty of making Cyaxares, as king of the Medes, carry on a war of five years with Lydia, while the Scythians were masters of his country. But it is pretty evident from the account of Herodotus that Cyaxares still reigned, though as a tributary to the Scythians, and that the dominion of the Scythians over Media rather consisted in constant predatory incursions from positions which they had taken in the northern part of the country, than in any permanent occupation thereof. It was probably, then, from B. C. 615 to B. C. 610 that the war between the Lydians and the Medians lasted, till, both parties being terrified by the eclipse, the two kings accepted the mediation of Syennesis, king of Cilicia, and Labynetus, king of Babylon (probably Nebuchadnezzar or his father), and the peace made between them was cemented by the marriage of Astyages, the son of Cyaxares, to Aryennis, the daughter of Alyattes. The Scythians were expelled from Media in B. C. 607, and Cyaxares again turned his arms against Assyria, and, in the following year, with the aid of the king of Babylon (probably the father of Nebuchadnezzar), he took and destroyed Ninus. [SARDANAPALUS.] The consequence of this war, according to Herodotus, was, that the Medes made the Assyrians their subjects, except the district of Babylon. He means, as we learn from other writers, that the king of Babylon, who had before been in a state of doubtful subjection to Assyria, obtained complete independence as the reward for his share in the destruction of Nineveh. The league between Cyaxares and the king of Babylon is said by Polyhistor and Abydenus (ap. Euseb. Chron. Arm., and Syncell. p. 210b.) to have been cemented by the betrothal of Amyhis or Amytis, the daughter of Cyaxares, to Nabuchodrossar or Nabuchodonosor (Nebuchadnezzar), son of the king of Babylon. They have, however, by mistake put the name of Asdahages (Astyages) for that of Cyaxares. (Clinton, i. pp. 271, 279.) Cyaxares died after a reign of forty years (B. C. 94), and was succeeded by his son Astyages. (Hdt. 1.73, 74, 103_106, 4.11, 12, 7.20.) The Cyaxares of Diodorus (2.32) is Deioces.
Respecting the supposed Cyaxares II. of Xenophon, see CYRUS.