The military historian Richard Holmes pointed out in one of his books that at the height of UK imperial power someone managed to rise from private soldier to Field Marshall and Chief of the Imperial General Staff and that apparently today an equivalent rise would be impossible:
Absolutely untrue, at least in a US context. Michael Boorda rose from the bottom of the enlisted ranks to become Chief of Naval Operations in the 1990s.
https://en.wikipedia.org/wiki/Sir_William_Robertson,_1st_Bar...