During the 1st century A.D./B.C., what was the deciding factor on who was recruited into the legions and who was recruited into auxillia units. By this time period, most of the legions were recruited in the provinces and I know that citizenship was a defining factor on whether the draftee was going to be in the legions or the auxillia. But, many auxillia units were recruited in the provinces like the Batavians out of present day Holland. I know that alliances with tribes would give Rome mass quantities of levies for the auxillia units during the late republic. I was also under the impression that Hadrian extended citizenship to all people residing in the provences, so by that time, where was Rome getting its Auxillary units from?