Darius II, originally called Ochus, was emperor of Persia from 423 BC to 404 BC.
Artaxerxes I, who died shortly after December 24, 424 BC, was followed by his son Xerxes II. After a month and a half Xerxes was murdered by his brother Secydianus or Sogdianus (the form of the name is uncertain). His illegitimate brother, Ochus, satrap of Hyrcania, rebelled against Sogdianus, and after a short fight killed him, and suppressed by treachery the attempt of his own brother Arsites to imitate his example. Ochus adopted the name Darius (in the chronicles he is called Nothos, meaning "the bastard"). Neither Xerxes II nor Secydianus occurs in the dates of the numerous Babylonian tablets from Nippur; here the reign of Darius II follows immediately after that of Artaxerxes I.
Of Darius II's reign we know very little (a rebellion of the Medes in 409 is mentioned in Xenophon), except that he was quite dependent on his wife Parysatis. In the excerpts from Ctesias some harem intrigues are recorded, in which he played a disreputable part. As long as the power of Athens remained intact he did not meddle in Greek affairs; even the support which the Athenians in 413 gave to the rebel Amorges in Carla would not have roused him, had not the Athenian power been broken in the same year before Syracuse. He gave orders to his satraps in Asia Minor, Tissaphernes and Pharnabazus, to send in the overdue tribute of the Greek towns, and to begin a war with Athens; for this purpose they entered into an alliance with Sparta. In 408 he sent his son Cyrus to Asia Minor, to carry on the war with greater energy. In 404 Darius II died after a reign of nineteen years, and was followed by Artaxerxes II.