Naming conventions

[Giannis K. Hoplite]

Both are correct. We usually use the second,but it's a matter of focus and expression. When the adjective follows the noun,and especially in the end of the phrase,you focus more in the adjective. For example two different imaginary phrases:
"He took charge of the Agrianes peltastas and attacked in the flanks"
And
"In the flanking maneuver he also used peltastas Agrianes"
In the second case it is not that the adjective before the noun would be wrong,but the whole "feeling" of the sentence would be a bit different. And certainly the focus wouldn't be so much in the origin of the peltasts,as in the fact that they were peltasts. But these are in no way definite rules and one could use both in either case.
Khaire
Giannis