Jewish Mercenaries
From the Letter of Aristeas we gather that Jews had served in the forces of King Psamtik II (e.g. of Egypt) (594 B.C.E.–589 B.C.E.), who waged war against the Ethiopians.
Source: Ben-Zvi, Itzhak. The Exiled and the Redeemed (p. 288); How the Septuagint Differs. Biblical Archaeology Review 2.2 (Jun 1976): 33-34, 38.; Mission To Alexandria Truth and legend about the creation of the Septuagint, the first Bible translation By Leonard J. Greenspoon.; The English translation used in this article is from R.J.H. Shutt, “Letter of Aristeas (A New Translation and Introduction),” which can be found in The Old Testament Pseudepigrapha, vol. 2, ed. James H. Charlesworth (Garden City, NY: Doubleday, 1985).