Before ascending the throne Artaxerxes was a satrap and commander of his father's army. Artaxerxes came to power after one of his brothers was executed, another committed suicide, the last murdered and his father, Artaxerxes II died. Soon after becoming king, Artaxerxes murdered all of the royal family to secure his place as king. He started two major campaigns against Egypt. The first campaign failed, and was followed up by rebellions throughout the western part of his empire. In 343 BC, Artaxerxes defeated Nectanebo II, the Pharaoh of Egypt, driving him from Egypt, stopping a revolt in Phoenicia on the way.
In Artaxerxes' later years, Philip II of Macedon's power was increasing in Greece, where he tried to convince the Greeks to revolt against the Achaemenid Empire. His activities were opposed by Artaxerxes, and with his support, the city of Perinthus resisted a Macedonian siege.
There is evidence for a renewed building policy at Persepolis in his later life, where Artaxerxes erected a new palace and built his own tomb, and began long-term projects such as the Unfinished Gate.
Artaxerxes III (Old Persian: 𐎠𐎼𐎫𐎧𐏁𐏂, Artaxšaçrā, "he whose empire is well-fitted" or "perfected", or Arta:"honoured" + Xerxes: "a king" ("the honoured king"), according to Herodotus "the great warrior") was the throne name adopted by Ochus when he succeeded his father in 358 BC. He is generally referred to as Ochus, but in modern Iran he is known as Ardeshir III (Persian: اردشیر سوم). In Babylonian inscriptions he is called "Umasu, who is called Artakshatsu". The same form of the name (probably pronounced Uvasu) occurs in the Syrian version of the Canon of Kings by Elias of Nusaybin.