Energetic Persian emperor whose forceful actions to suppress revolt & centralize authority restored the borders of his far-flung empire, but whose brutal tactics & harsh treatment of opponents created conditions for its disintegration after his death. The fourth son of long-reigning Artaxerxes II (404-358 BCE), Ochus acted to take control of affairs even before his indolent aged father died, by instigating the elimination of his older brothers. On assuming the throne, he adopted his father's throne name & eliminated more than eighty relatives (both male & female) whom he saw as potential rivals.

Then turning his attention to western satrapies that had gotten used to acting independently in his father's last years, he ordered local governors to disband their armies & defeated the few in Asia Minor who dared to defy his order. However, his first attempt to regain Egypt, which his father had lost to a native dynasty, was thwarted (350 BCE) & that failure led other provinces on the Mediterranean rim to rebel. This so angered Ochus that he returned with a huge imperial army that destroyed the Phoenician city of Sidon, which had led the revolt, impaling hundreds of its citizens on javelins even after their surrender (347 BCE). Then he led his army south to reconquer Egypt (346 BCE). When the native pharaoh (Nectanebo II) fled south to Nubia, Artaxerxes leveled the walls of Egypt's major cities & unleashed his soldiers to pillage & plunder palaces & temples alike.

His successful generals were granted control of vast regions that put nominally autonomous satrapies under centralized control. The naval commander, Mentor of Rhodes, was granted control of the whole Mediterranean rim, while the Egyptian eunuch Bagoas was sent to Babylon, charged with administration of eastern satrapies. The  latter was eventually made chiliarch (grand vizier) of the whole empire & restored civil order for half a dozen years.

The emperor's untimely death, however, jeopardized Bagoas' authority, so he poisoned the emperor's oldest sons & installed the youngest, Arses, as his successor. While the 1st c. BCE Greco-Roman historian, Diodorus of Sicily, claimed Bagoas poisoned Ochus himself, Persian records indicate that the latter had died of natural causes. At any rate, with the death of Artaxerxes III, Persian power began to fragment & his subjects' widespread resentment of the brutal tactics which he used to restore his empire created the conditions for its collapse in less than a decade.   

References:  Diodorus Siculus, Library of History 16.40-52, 17.5.
                   Arrian, Anabasis of Alexander 2.14.
                   Plutarch, Parallel Lives: Artaxerxes 26-30.
                   Justin, Epitome of Trogus' Philippic History 10.1-3.
                   Josephus, Antiquities 11.7.1.

 Other resources on line:

• Artaxerxes III - annotated article in Encyclopedia Iranica.

• Artaxerxes III Ochus and His Reign - N. C. Hirschy's 1909 study of allusions to Ochus' reign in Old Testament sources [Internet Archive].

• Artaxerxes III - R. Gottheil & E. Meyer assess Persian emperor's character & accounts of his impact on Jews [from 1906 Jewish Encyclopedia].

• Persepolis: Tomb of Artaxerxes III - Jona Lendering's illustrated description of the last of the royal tombs in the ancient Achaemenid capitol [Livius.org].

• Artaxerxes III -  annotated entry in Wikipedia's web.