Berthold is the author of the book Rhodes in the Hellenistic Age (Cornell University Press, 1984)[3] and of the self-published Dare to Struggle: The History and Society of Greece (2009).
in 1969 with the thesis The Battle at Marathon[5] and completing his Ph.D. in 1971 with the dissertation Rhodian Foreign Affairs 205-164 B.C..[6] After a year as a part-time lecturer at Cornell, he joined the faculty of the University of New Mexico in 1972 as an assistant professor.
[7] On the day of September 11, 2001 terrorist attacks Berthold, an extremely popular lecturer, quipped to his large Western Civilization and Greek History classes that "Anybody who blows up the Pentagon gets my vote,"[8] which was the kind of remark students expected from him but was in this instance in bad taste.
After a university investigation, Berthold received an official reprimand, signed a confession and was removed from the freshman Western Civ course he had been teaching for thirty years.
[10] In 2005 he was barred from a local religious conference center after presenting archaeological research contradicting the biblical story of the Exodus.