The most conspicuously brave of all the German tribes in Gaul, the Batavi, hold little of the river- bank, but do hold the Rhine island. They were once a section of the Chatti, and on the occasion of a civil war they migrated to their present home...

Tacitus, Germania, 29

Cohors I Baetasiorum civium Romanorum ob virtutem et fidem was a part-mounted unit raised in Lower Germany before 103ce. It was awarded Roman citizenship because of conduct in the conquest of southern Scotland, 139-142 ce. The cohort was at Maryport on the western end of Hadrians Wall from the mid 160s to 180s. Their officer, T. Attius Tutor, prefect, went from Maryport to become tribune of legio II Adiutrix, based at Acquincum (Budapest), prefect of ala I Tungrorum Frontoniana, in Dacia, and prefect of ala I Batavorum milliaria, also in Dacia.