DARIUS THE GREAT, one of the greatest rulers of the Achaemenid dynasty, who was noted for his administrative genius and for his great building projects. Darius attempted several times to conquer Greece; his fleet was destroyed by a storm in 492, and the Athenians defeated his army at Marathon in 490.

Darius was the son of Hystaspes, the satrap (provincial governor) of Parthia. The principal contemporary sources for his history are his own inscriptions, especially the great trilingual inscription on the Bisitun (Behistun) rock at the village of the same name, in which he tells how he gained the throne. The accounts of his accession given by the Greek historians Herodotus and Ctesias are in many points obviously derived from this official version but are interwoven with legends.

According to Herodotus, Darius, when a youth, was suspected by Cyrus II the Great (who ruled from 559 to 529 BC) of plotting against the throne. Later Darius was in Egypt with Cambyses II, the son of Cyrus and heir to his kingdom, as a member of the royal bodyguard. After the death of Cambyses in the summer of 522 BC, Darius hastened to Media, where, in September, with the help of six Persian nobles, he killed Bardiya (Smerdis), another son of Cyrus, who had usurped the throne the previous March. In the Bisitun inscription Darius defended this deed and his own assumption of kingship on the grounds that the usurper was actually Gaumata, a Magian, who had impersonated Bardiya after Bardiya had been murdered secretly by Cambyses. Darius therefore claimed that he was restoring the kingship to the rightful Achaemenid house. He himself, however, belonged to a collateral branch of the royal family, and, as his father and grandfather were alive at his accession, it is unlikely that he was next in line to the throne. Some modern scholars consider that he invented the story of Gaumata in order to justify his actions and that the murdered king was indeed the son of Cyrus.

Darius did not at first gain general recognition but had to impose his rule by force. His assassination of Bardiya was followed, particularly in the eastern provinces, by widespread revolts, which threatened to disrupt the empire. In Susiana, Babylonia, Media, Sagartia, and Margiana, independent governments were set up, most of them by men who claimed to belong to the former ruling families. Babylonia rebelled twice and Susiana three times. In Persia itself a certain Vahyazdata, who pretended to be Bardiya, gained considerable support. These risings, however, were spontaneous and uncoordinated, and, notwithstanding the small size of his army, Darius and his generals were able to suppress them one by one. In the Bisitun inscription he records that in 19 battles he defeated nine rebel leaders, who appear as his captives on the accompanying relief. By 519 BC, when the third rising in Susiana was put down, he had established his authority in the east. In 518 Darius visited Egypt, which he lists as a rebel country, perhaps because of the insubordination of its satrap, Aryandes, whom he put to death.