I'm reading Horus Rising right now and I don't get the EC ranks. Eidolon is in charge of a company of a 100 marines (or at least the company that they sent to Murder was that big) and Lucius and Tarvitz are captains despite seemingly being in charge of just a single squad. So are they just sergeants with a fancy title? How come they get such fancy wargear for a sargeant? Meanwhile Loken, also a captain, has a whole company of around 600 at his command.