Well, why would they? If they're not military, its not their duty. If they're not religious, they're not doing it for faith.

I know that some merchants scrape together private security forces and mercenaries to do military stuff for them, though the ones I know of were heretics. I suppose nobles could use their private guard, but they'd probably send them against a rival noble more than waste them against enemies of the Imperium that the Guard are supposed to be fighting.

At best, you could probably do something with Rouge Trader houses, but they'd do whatever they do for profit or glory or to explore new stretches of galaxy. They probably wouldn't need an army, and an influential enough one to get one could probably just call in the Guard for a favor.

It's not impossible, there's just very few good reasons or examples, especially since 40k is a setting build primarily around a wargame, so of course the fluff is going to focus on things you can use in the wargame.

>>46398984
>>46398984
Most noble houses have armed forces. Some inquisitors do aswell, rogue traders most definatly have troops, as do the forge and feudal worlds.

>>46399423
>Well, why would they?
Prestige, I figure. Maybe they're trying to show-up the other houses in the sector and impress the Ecclesiarchy or Adeptus Terra in order to gain more power in their region.

>>46398984
Nobles have security forces I'm sure to protect their holdings. As well as spies and assassins. Think cyberpunk corporate security. Not massive in scope, but well armed and reasonably well trained.
But actual armies? Doubtful, that's what the PDF and Guard are for.

>>46399657
Frequently this.

>>46399484
This is also true.

Technically every planet's PDF is meant to be independent of the wider Imperial command structure; the Imperium does not impose draconian law on every planet by the Adeptus Arbites. Local and lower authorities like local planetary enforcers and the PDF or local militia will handle military defense, garrison duties, and law-enforcement. This essentially means every noble lord or planetary governor has their own house troops. Every single planet is the Imperium is this way, and because of it, the Imperium's diversity basically knows no limits, because every planet is different.

The only times the Imperium gets involved are the tithe, the event of the tithe being threatened, and Inquisitorial matters.

Which brings >>46399423 's assessment into play.

Every planet's power games and internal politics are where the vast majority of private armies will be involved. If the planet's ever invaded, it's likely those private armies will see action fighting the enemies of Man, but they'd have few reasons or motives to commit them to wars offworld.

>>46398984
The AdMech?
Inquisition?
Local nobility?
Rouge Traders?

Take your pick.

>>46401028
The Admech and Inquisition have their own militaries and militant arms though. You can consider them both under military or religious branches.

>>46401059
I would argue against that.

They each have their own seat on the Council of Terra, which makes them distinct branches of the Imperium.

>>46401480
But the Guard and the navy have seats there as well. Even the Sisters of Battle have a position, though it hasn't been filled in recent centuries.

bump for interest

>>46401480

You mean in the Senate. High Lords are a very small subset, and while certain imperial institutions nearly always have their leader as a High Lord, this isn't guaranteed and every Imperial institution has at one point or another been excluded.

Having or not having a seat at any given time changes how much power the institution wields, but doesn't actually officially change anything.