If Dan Abnett is to be believed (which admittedly he sometimes isn't) If there isn't a proper leader like a Lord General on the planet, the highest ranking Guard Infantry officer in the field is in charge of operations. so most of the time the ghosts (who only have a colonel) have to answer to a regiment with a General. However there is a time (the book with Vervunhive in) where Gaunt gets to order around a General of a Leman Russ Regiment. Which is justified with "an infantry officer takes precedent over an armour officer"

Wow: I wished that one worked out in the real world. That's a bit of awful writing. I'd rather he'd have got around it by pulling the 'I'm a commissar' thing.

'Sorry, General: I might must be a Captain, but you're a tanker, and I'm PBI, so I outrank you'

Narkasis Broon said:

Also this might be a complete lie, i'm hoping someone will shed light on it because it's niggling at my memory

I have heard stories that there is a particular unit of either British of American special forces where the highest rank you can attain within this organisation is sergeant, but a sergeant from this organisation will often be able to exert influence on conventional military units even if their leaders outrank him, because the organisation is so well respected. just as a side note

There's no formation of troops within the British military where rank is capped at Sgt. Although rank within specialised units is harder to attain due to their size, so tends to get a little more respect.

All armed forces have a tradition of listening to the opinions of experienced/specialised/special forces staff and treating their opinions as more valuable because of their experience (Hell: Nothing would ever get done if junior officers didn't let their CSMs pretty much run things!). But there's a big difference to having your opinions considered by those of senior rank and actually issuing orders to them.

In the US armed forces Sergeant's are the top of the enlisted tree. The trick is to get to sergeant you've got to prove yourself by enlisting and starting at the bottom (well, presumably).

Officers start off being able to give orders and command groups of troops fresh out of school.

Given that, in a combat situation a veteran sergeant is going to be able to provide real insight and good ideas to an officer, junior or otherwise, who may not have that combat expereince. The good ones listen and learn.

As for the guard and officers commanding other formations, it all depends on how the guard is organized, and it's 100% believable, at least to me, that in the Imperium’s infinite wisdom they have ranks within ranks and allow Infantry commanders to boss around tanks, given that the vast bulk of the guards army consists of men walking. It may not be the most logical, but this is the IG after all.

Narkasis Broon said:

It's been a while since I read it, but I thought part of that was that it was a PDF tank regiment and Gaunt had played the Commissar card to oust the officer commanding the whole defense due to traitorous actions.

All Spoilers

He does play the commissar card to get rid of General Sturm. but then him and General Grizmund (I think) meet up with him and is like 'I will defer to the infantry commander.' at which point Gaunt is like u go fight with your regiment, I'll organise defense of the Hive

Stupid forums and their stupid editing:

CONTINUE SPOILERS...

Narkasis Broon said:

All Spoilers

He does play the commissar card to get rid of General Sturm. but then him and General Grizmund (I think) meet up with him and is like 'I will defer to the infantry commander.' at which point Gaunt is like u go fight with your regiment, I'll organise defense of the Hive

Everyone else was dead, and the two highest ranking officers were Grizmund and himself. Grizmund deferred to the Infantry commander primarily because that was standard proceedure- there is a really wierd line about that in there, which honestly I just attributed to the guard being as backwards as any bureaucratic machine. They did however agree on their plan, and Grizmund probably could've fought for control but Gaunt was pretty respected by field commanders.

Plus given how completely ****ed the hive looked at that point I wouldn't want to be the guy in command would you?