Detachments were limited to one "top tier" officer (a Commandant), with specific hierarchy rules for designating the army's Warlord. New Units & Characters
Received "free" special weapons, encouraging larger, diverse squads. 10th Edition comparison for your readers? 9th Edition Astra Militarum Codex Pdf
: The "Voice of Command" system was revamped with three tables of 18 total orders, including new Perfectus Orders for Commissars. Detachments were limited to one "top tier" officer
If you are hunting for the 9th edition PDF, you likely own or want to build the new models that debuted alongside it: 9th Edition Astra Militarum Codex Pdf