Star Mercs
“The Imperium is a remote centralised government possessed of great industrial and technological might, but unable, due to sheer distances and travel times to exert control at all levels everywhere within its star-spanning realm. Conflicting local interests often settle their differences by force of arms with Imperial forces only intervening when conflicts threaten either the security or economy of the area as a whole.”
(Mercenary, Book 4, Traveller, GDW 1978.)
Mercenary units have always been a common part of the Imperium and in the chaos and collapse of the civil war, have flourished. With the vacuum of the disintegration of Imperial rule and the wholesale return of piracy and enemy invasions their numbers have rapidly grown. Of course the thin line between legitimate star merc and pirate is a thin one that has often been crossed. In many parts of the collapsed Imperium they are begrudgingly seen as a necessary evil as naval and marine assets are spread thin. Star Mercs commonly contract for convoy escort duties, trade missions and their speciality of system defence.
It has long been a common Naval practice that local SDB & second line units are run by colonial and planetary navies with their own crews and personnel. The Imperial Navy thus being free to run ‘proper’ jump capable and higher tech craft. Of course the large Imperial monitors and battle riders are an exception o this rule but with none present in any numbers it is an irrelevancy.