Auxilia units

[D B Campbell]

But my question is how quick would the identity have been mixed up by other tribes and maybe even other cultures?

This ... is what happens in Gaul, where the recruitment areas for auxiliary units broadened over time (and especially after the Civilis revolt), diluting the originally strong ethnic identity of the auxiliary units.

Equally, if the bulk of your recruits come from Spain, Gaul and Thrace, there's bound to be a change in the ethnic make-up of any reinforced unit. This is what (we think) happened to the ala Gallorum et Thracum Classiana: probably starting as a Gallic unit (the ala Classiana), it received so large an influx of Thracians that it changed its name to reflect the new make-up.