Note 184 — THE AUXILIA DURING THE FIRST TWO CENTURIES A.D.
Reading edition
The crucial passage is of course Tac. Ann. xvi. 13 ‘eodem anno dilectus per Galliam Narbonensem Africamque et Asiam habiti sunt supplendis Illyrici legionibus’, which appears to come from the acta senatus. But the evidence for imperial control is very strong, and the Senate may merely have been consulted as a matter of courtesy. Tiberius used to bring military questions before the Senate in the same way—‘de legendo vel exauctorando milite ac legionum et auxiliorum descriptione’, Suet. Tib. 30—without giving up his prerogative.