Roman Legion in late Antiquity

[Macedon]

At least according to Dio, the Batavi need not be Batavians themselves as they were a picked cavalry corpse, that was called thus after Batavia, the island in Rhine, where the best horsemen are. So, the actual units might be comprised of German or even (although it would be my personal opinion that a certain cultural uniformity was maintained) non-German horsemen as he he seems to suggest. I have to say here, that the era in question is not one I know much about, since I only lately have occupied myself in depth with the relevant sources, so I do acknowledge that other sources I have not studied yet may easily claim or prove otherwise.

"ξένοι τε ἱππῆς ἐπίλεκτοι, οἷς τὸ τῶν Βατάουων ἀπὸ τῆς Βατάουας τῆς ἐν τῷ Ῥήνῳ νήσου ὄνομα, ὅτι δὴ κράτιστοι ἱππεύειν εἰσί, κεῖται·" 55.24.7.