Roman Legion in late Antiquity

[Robert Vermaat]

They couldn't have been recruited from the area the Batavi were formerly settled in because that Area was full of Frisii in 297 AD onwards. Any units from that area would have been known as "Frixiavonum"

Nono, the Frisii are not there at all. We see some early movement from Drenthe (eastern parts of The Netherlands) towards the Rhine, and only a few across it, but by far the most keep returning to the areas north of the Rhine. This continues until the later 4th c., when we see the first settlers in Brabant and finally Toxandria. During the early 5th century the original settlements in Drenthe begin to empty, until they are empty after the second half of the 5th c.

Frisians become part of the move towards Britain at that time, but their lands from Schleswich to Zeeland are actually settled by what we would call Danes and Saxons. Only after the middle of the 6th century do we see these peoples arrive at the Rhine. No Frisians present in the old Batavi lands therefore during the 3rd-4th centuries.