I.e, a cadre of high-ranking professional soldiers responsible for directing military policy and administration for the Empire as a whole?
To elaborate: if we're narrowing down a time period, how about Augustus to the 3rd century crisis?
Fantastic question. Would you mind getting more specific? That question covers a few hundred years of history. Maybe even thousands. I would assume you are asking about O ctavian-esque Rome? Maybe even Agustus?