AWA299 - Who or what made the decisions about where Roman army units were based or moved around the Empire?

'A question for Murray, who or what made the decisions about where Roman army units were based or moved around the Empire? I am presuming if it were a vexillation from Hadrian's Wall to York, it would be a local commander's decision, but what if it was a cohort sent from York to Gaul, ie between adjacent provinces? Was that worked out by the military staff of the respective governors? And then what about legions moving from, say, Gaul to Syria for military reasons or even for civil engineering projects? Was there a general staff in Rome comprised of ex-field generals, gnarly old centurions and civil servants, or was it down to the Emperor/Senate (depending on the period) to plan it all?' Thanks for that question Keith.   Join us on Patron patreon.com/ancientwarfarepodcast