Smith's Bible Dictionary

1. The first Artaxerxes is mentioned in Ezr_4:7 and appears identical with Smerdis, the Magian impostor and pretended brother of Cambyses, who usurped the throne B.C. 522, and reigned eight months.

2. In Neh_2:1, we have another Artaxerxes. We may safely identify him with Artaxerxes Macrocheir or Longimanus, the son of Xerxces, who reigned B.C. 464-425.

Taken from: Smith's Bible Dictionary by Dr. William Smith (1884)