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geeksquared
19-08-2010, 15:16
I know the listed strength is 1000 marines minus casualties from ongoing ops but I reckon it has to be a lot more than that.

Begin with the core strength. Each company is 100 normal marines plus a captain and a standard bearer and sometimes his personal guard so you've already got 2-7 extra marines per company. for a total of between 20-70 extra marines. Then there is the chapter master, his bodyguard, the chapter standard bearer all told thats another 5-10.

Next we have all the guys in seperate divisions of the chapter. Chaplains, Apothacaries, Librarians, Techmarines,Fleet officers and (technically) Dreadnaughts.

After those there are all the guys who drive the tanks. Each company has one rhino per squad plus all the different tanks. They can't be crewed by the squad they transport because then when they disembark they'll be leaving a valuable vehicle unattended. Each Rhino needs and Driver and each tank of any type needs a Driver and between 1 and 3 gunners. There aren't enough guys in the reserve companies to drive all the vehicles of the chapter so unless there are several hundred Techmarines dedicated to operating vehicles there must be designated drivers in each company.

Lastly there are all the marines who are to badly injured to continue as combatants but are still fit enough to perform a task for the chapter like administration or initiate selection and training.

By my reckoning a single chapter could be up to 2000 strong when at full strength. What do you guys think?

mrln68
19-08-2010, 15:29
No.

1000 is the rule - but it is normally broken. The current Vanilla Marines Codex includes a break down of the Ultramarines (surprised?) and they are likely one of the largest normal marine chapters (also a much more detailed one in the 3rd Ed. Codex). You can take a few minutes and add everything up yourself - though IIRC it was around 1500 or so assuming that all the vehicles had their own crews and all the command structure was not counted within the company structure.

massey
19-08-2010, 16:07
Chapters have a variable size. Don't think of it as a "hard cap", there is some wiggle room.

You've normally got a 1st company. These are the veterans, and they're nominally capped at about 100, though most active chapters won't have enough veterans to fill that. These guys have centuries of combat experience, and so any losses here take quite a while to recover. Just guessing, I'd say an average chapter has between 50-80 of these guys.

Then you've got the 4 battle companies, where you've got about 100 marines in each. Likewise, that's 100 marines when they're "full", since these guys do the majority of the fighting, they'll take the majority of the casualties. So their numbers will always be in a bit of flux, between guys dying, guys moving up from reserve companies, guys getting promoted into the 1st company, etc. Most chapters would try to keep their battle companies full.

Then you've got your 4 reserve companies. While they are technically supposed to have 100 members each, they're less important than the battle companies, and probably would not always be at full strength. It might not be uncommon for them to be as low as half strength, depending upon how recently the chapter had been engaged in heavy combat. Likewise, it's easier to hide your numbers in a reserve company, so if a chapter is over-strength, this would probably be the place to put your extra guys.

Then you have the 10th company. There is no set size limit on scouts, since they're not considered full-blood marines yet. Most chapters that see a lot of combat would keep up a very steady recruitment drive, possibly having several hundred scouts at any one time (much like Nebraska football used to do with their walk-on program -- the NCAA limits schools to having 85 scholarship players, so Nebraska would have about 300 local boys who would work out and practice with the team in hopes that they might one day earn a scholarship).

Then you'll have the associated staff guys, from command squads to rhino drivers. Technically, vehicles are driven by guys from the reserve tactical companies, the 6th and 7th. And the staff positions could be filled by guys within the standard company organization, as well. They don't need extra guys. A chapter that had just been through heavy combat and did not have a huge group of scouts waiting to step up could be "full strength" (on paper) and have maybe 800 guys. On the other hand, a chapter could also squeeze dudes into every possible opening (special assigned honor guard, chapter fortress security squad, sternguard squad, etc) and be trucking around with 1500 to 2000 guys. I'd imagine that your average chapter probably struggles to keep 1000 active battle brothers, that their recruitment just barely offsets the losses they suffer in battle. Other chapters, probably 1st founding, have the luxury of over-strength reserve companies, guys on permanent special assignment, fully manned honor guard squads, etc. They look the same on paper, but while the average chapter would have empty placesettings at the dining hall, the Dark Angels are bringing out extra tables and chairs, and have dudes sitting over on the couch playing X-Box.

wxyz
19-08-2010, 16:15
Here's a good article about it:

http://www.bolterandchainsword.com/index.php?autocom=ineo&showarticle=291

magath
19-08-2010, 16:29
The way I look at it is like this:

Every company will have 106 marines, which is 100 marines, commander and full command squad.
On top of that, you have a number of additional staff. Say, roughly 10 tech marines, 30 dreadnoughts, 10 chaplains and about 6 librarians, your quickly looking at over 1100
The 10th company has no fixed size, even the Exorxists run two scout companies, so your maybe looking at an additional 100 or so bodies there.

As a rough guess, I reckon 900 line marines (inc first company) and about 350 ancilliary blokes including scouts.

The vehicle thing, I explain mine as being driven by chapter serfs and servitors, so it saves any BS about a secret tank driving company and so on.

The real interesting thing comes when you consider non marine fighting units, like chapter serfs, servitors and so on, a chapter could feasably keep thousands of helots on staff.

Marshal Argos
19-08-2010, 16:30
There's a big article over on B&C about this very topic, I'm just lazy to go look it up. If you do a search here on Warseer you'll find that this comes up pretty often and the general consensus is that yes, most chapters are larger than 1k. Usually anywhere from 1250 to 1500.

here a few examples:
http://www.warseer.com/forums/showthread.php?t=252897&highlight=chapter+size
http://www.warseer.com/forums/showthread.php?t=248356&highlight=chapter+size

@Massey; do you have your answer to this question saved? I seem to remember you always replying with pretty much the same answer.

massey
19-08-2010, 18:18
@Massey; do you have your answer to this question saved? I seem to remember you always replying with pretty much the same answer.

Nah, I'm just repetitive. :)

SharpSilver
19-08-2010, 19:47
Really depends on the Chapter.

Some Chapters such as the Black Templars, Space Wolves and Salamanders do not follow the Codex Astartes as strictly as the vast majority of second founding Chapters, therefore, their 'Companies' or 'Great Companies' (In regards to the Wolves and Salamanders) have more per Company than any other Chapter, and the Black Templars use 'Fighting Companies' within their Crusade Fleets, which in the words of Black Templar Fluff, can be 10 marines or 100 marines, or more.

The Space Wolves are probably the most Anti-Codex Astartes of the three, because they don't follow it really in any format. The only act Leman Russ did to please Robute and his Codex-Astartes lark was to reduce the Size of the Legion to Chapter-size in accordance, but apart from that, nearly nothing else matters from it because each Great Company maintains it's own fleet, Scouts, and is specialized for different tasks, with nothing set in stone. One Wolf lord may prefer Mechanised assault where another Drop Pod engagements, this allows for far more flexibility instead of the static- 'textbook' rubbish sprouted from Robute. :D

But enough of the Wolves. 99.9% of Chapters will stick to the 1,000 Fighting Strength + Support personnel number spread amongst 10 Companies with the 1st being Veteran and the 10th being Scout.

Chaplain Dionitas
19-08-2010, 20:20
Rough Ballpark figure on the B;ack Templars was somewhere around 4k+ Marines. Most of your non-codex chapters will normally have larger numbers

starlight
19-08-2010, 20:34
Wolves and Templars have been estimated as large as 4-6K overall, although a few have placed them as high as 10K depending on how you read the numbers... :shifty:


The Dark Angels (due to the whole Unforgiven thing) essentially run at least that large (6-10K), as do the Ultramarines (due to the Ultramar thing). While technically they both adhere to the *1000 Marines per Chapter* rule, they can command much, much larger forces due to their relationships with their Successor Chapters.

Lupe
19-08-2010, 20:34
The exact figure stopped being relevant after the Second Founding chapters first came into being. And even then, it wasn't relevant if there were 900 or 1100 marines in a chapter. So long as there weren't 20 thousand or more marines operating as a single, unified force, under command of one superhuman but still fallible general, a few squads' worth of marines wouldn't attract any reprimands from the High Lords. Besides, given the length of scout training one has to undergo before becoming a marine, it'd be impractical to even attempt to limit recruitment when suitable candidates are found.

And I do believe the scout company can still be as large as the chapter sees fit. Only full fledged marines count towards the 1000 figure. Neither do the dreadnoughts and the auxiliary personnel where that occurs.

Still, the Space Wolves are probably sitting at around 3000 marines, and the Black Templars somewhere between 8-10 thousand, and they've been openly doing so for thousands of years.

At any rate, for Codex chapters, the 1000 figure does not mean that the 1001st marine gets put on stasis until someone dies, or anything.

Read it more as 1 Chapter ~ 1*** marines.

Col. Tartleton
20-08-2010, 01:06
I wouldn't be surprised if the scout "company" was still a Pre Heresy 1,000-10,000 men in most chapters. The Scout Captain acting more as an administrator type while the actual units are under the leadership of veterans acting as Veteran Sergeants who probably oversee 50 odd scouts a piece. You have to put the machine in scale.

Basic marine scouts are comparable to our modern day Marine Recon Scout Snipers albeit with futuristic gear and stuff. However in our modern military these are the pinnacle of human fighting machine. In the Adeptus Astartes these are a bunch of wannabes who think they've got what it takes to play with the big dogs. The united states with a pool of recruits in the tens of million range has over 200,000 Marines. There are only three battalions of Recon Marines. Only a fraction of those also possess the skill set to be snipers.

So with a pool of millions being recruited from only a few hundred may qualify to become Space Marine Scouts. On top of this, they serve in the role of Scout for years in high risk high value situations while being evaluated and pushed to breaking time and again. Losing half their number in that time is probably low balling it. I'd expect 3 of every 10 scouts to reach a position as Full Marines. Full Marines are now to special forces what special forces are to civilians. On top of that you have Veteran Marines who serve as Full Marines for decades to centuries... These are one in several billion men. This is why there is a marine for every planet...

Did I mention how tough the Primarchs were. :D

Lord_Crull
20-08-2010, 02:32
One Wolf lord may prefer Mechanised assault where another Drop Pod engagements, this allows for far more flexibility instead of the static- 'textbook' rubbish sprouted from Robute. :D


That's not quite how the Codex works. It revolves around tactical flexbility. You go with the approach that works best in a paticular situation. So rather than being specialized in one tactic, battle companies can be expected to perform equally in all aspects of warfare.


Alongside the Ultramarines, the Imperial Fists have become the epitome of Codex doctrine. All ranks are able to make tactical decisions and are encouraged to act on initiative. The Imperial Fists combine all arms in flexible balanced battle groups each of which can present an opponent with a diversity of threats then press their attack so swiftly that the foe is overwhelmed before he can react.

In that way they are more flexible than Great Companies who tend to favor one type of warfare. (Of course I'm not saying that the Wolves can't do that all when required, being specialised like that tends to leave one less skilled in other areas. Ultramarines go with what works practical)

As for the number issue, I always took that to be a 1000 line brothers with the extra number simply being support staff added on.

Post
20-08-2010, 12:14
There seem to be two extreme camps of Codex Adherents, those who claim it as their holy book and are fanatical in their dogma, Ultramarines, Sons of Gulliman and those who consider it to be more of guidelines than actual rules, with minor deviations here and there, like the Iron Hands, Dark Angels.

Lord_Crull
20-08-2010, 12:25
There seem to be two extreme camps of Codex Adherents, those who claim it as their holy book and are fanatical in their dogma, Ultramarines, Sons of Gulliman .

I dont recall anything that states that the Sons of Guilliman chapter follow it religously, maybe you are thinking of the Black Consuls?


and those who consider it to be more of guidelines than actual rules, with minor deviations here and there, like the Iron Hands, Dark Angels.

The Iron Hands don't follow it at all. From what I recall reading their Index Astartes article they have some pretty heavy deviations.

Leftenant Gashrog
20-08-2010, 13:26
A Codex chapter is 1,000 marines in the same way that a kilobyte is 1,000 bytes.

The fact that a chapter has more than 1,000 marines is as serious a problem to the Imperium as a kilobyte having more than 1,000 bytes is a serious problem to the average computer user.

ChrisMurray
20-08-2010, 15:44
As has been shown before it's not an exact number. It seems to be one of those legal issue type numbers, I always assume it to be 1000 battle brothers howver a captain etc isn't a battle brother, he's a captain ;)

In the space wolves codex it says that Ragnar(sp?)'s great company has around 200 marines and is by far the largest.

Mike_the_magi
21-08-2010, 21:51
The way I see it from what I have read is...

At full Strength you have the 9 companies each of 100 Marines plus command staff, plus vehicle crews, plus support staff.

The Scout squad I would see as being larger than 100 due to a large attrition rate of dead scouts and those who don't make the grade so it will need to be larger to supply the need for new marines. Obviously this would also come with command staff, vehicle crews, instructors and support staff.

Then we have the additional stuff like the armoury, the Chaplaincy, the Librarians, the Chapter command staff. This would also have serfs and support staff.

So as a Vague Estimate I would say the average chapter is around 1200-1500 Actual Space marines, including command Staff and Vehicle crews. Then supporting that would be around ten to fifty thousand serfs, servitors, ships crew, simple armourers, servants, dogsbodies, toadies and Buerocrats which keep the place running.

After all... is your average Space Marine Captain gonna want to cook his own meals or do his own accounts? No... he wants to be out there smiting the enemies of the Empire.

Well thats my opinion anyway, and its what I am going with as I slowly build a Space Marine company.

SharpSilver
21-08-2010, 21:59
In the space wolves codex it says that Ragnar(sp?)'s great company has around 200 marines and is by far the largest.

Logan Grimnar's Great Company is the largest, and Ragnar Blackmane's is second to that.

Ragnar's Great Company boasts 'Almost 200 battle-hardened Warriors', which doesn't suggest that number is including the Blood Claws who might not be Battle-hardened. Therefore a actual number could be even higher. Perhaps closer to the mid 200 mark. Or perhaps Ragnar's Company is fortunate in the sense that every member is battle-hardened, which is unlikely because every Great Company, as do Codex Chapter's Companies, regularly recruit to maintain their numbers and replace the dead.

starlight
21-08-2010, 22:05
Although I recall a bit in the background that says that the remnants of the old Great Wolf's Great Company effectively becomes part of the new Great Wolf's Great Company (or the new one absorbs the old one, which is effectively the same)...which could be read as it being substantially larger than many people think... :shifty:

N0-1_H3r3
21-08-2010, 22:25
Although I recall a bit in the background that says that the remnants of the old Great Wolf's Great Company effectively becomes part of the new Great Wolf's Great Company (or the new one absorbs the old one, which is effectively the same)...which could be read as it being substantially larger than many people think... :shifty:
Well, there is the chapter command (which would originally have been Leman Russ's forces, but which now just covers support assets, dreadnoughts and the like), which is notionally distinct from any one Wolf Lord's Great Company, but which ends up being part of the Great Company of whichever Wolf Lord becomes Great Wolf.

So, if Logan Grimnar died in battle, his Great Company would be commanded by a successor chosen from amongst his Wolf Guard... but the Command section would go to whichever Wolf Lord is chosen to be the new Great Wolf (Ragnar Blackmane, for example), who in turn would replace their personal heraldry with the Wolf That Stalks the Stars heraldry of Leman Russ.

geeksquared
22-08-2010, 01:24
A Codex chapter is 1,000 marines in the same way that a kilobyte is 1,000 bytes.

The fact that a chapter has more than 1,000 marines is as serious a problem to the Imperium as a kilobyte having more than 1,000 bytes is a serious problem to the average computer user.

But when you're dealing with Tbs of data those pesky 24 extra bytes really add up and then they really are a problem. if each chapter has 1024 marines rather than 1000 and there are roughly 1000 chapters then there are 24,000 marines unaccounted for.

Thats an entire pre-heresy legion!

callsign-husker
22-08-2010, 05:34
The Codex (Imperial guidelines layed down by Guilleman not GW ruleset) outlines a preferred Chapter composition of ten companies of 100 marines + Captain, Chaplain and other command staff. Add to that Fleet and vehicle Astartes crewmen, the Librarius, Armourers, Techmarines, Dreadnaughts, Chapter command staff, equerries, servitors and non-astartes fleet crewmen.
A chapter easily comprises a couple of thousand (minimum) plus a various unspecific number of scouts.
The guideline points more towards limiting a chapter to around a thousand FIGHTING men, limiting it's power and aiming to prevent mutiny a la the Horus Heresey, and it is just a guideline, each chapter will vary in numbers Space Wolves being a notable example of this. It's the 40k equivelent to a British Standard, it's a guideline, not immutable law.

massey
22-08-2010, 14:05
But when you're dealing with Tbs of data those pesky 24 extra bytes really add up and then they really are a problem. if each chapter has 1024 marines rather than 1000 and there are roughly 1000 chapters then there are 24,000 marines unaccounted for.

Thats an entire pre-heresy legion!

So what? The purpose isn't to limit the number of Space Marines overall. The purpose is to divide up their power so that one guy can't start a civil war. An extra 20 thousand or 50 thousand or however many marines isn't a big deal, when they're spread out over 1000 chapters.

Basically, if, once you count every support guy and honor guard and dude on a starship, Chapter X has like 1300 marines, it's not a big deal. Because their power isn't appreciably greater than a chapter that has exactly 1000 guys. Sure, they've got a bigger number of guys, but it's still in the same ballpark. What they're trying to avoid is one chapter having 50,000 guys.

starlight
22-08-2010, 14:32
Which is what they have with outfits like the Dark Angels and Ultramarines and their respective Successors...just in a different name... :shifty:


Pretty much *everything* that a given power in 40K has tried to avoid has come to be under a different name/guise...

Lord_Crull
22-08-2010, 14:47
Which is what they have with outfits like the Dark Angels and Ultramarines and their respective Successors...just in a different name... :shifty:


Not quite. The Dark Angels chapters only measure up to about 14,000 or so combined, that's hardly 50,000 men. The second is actually rather strange when we compare the 5th edition fluff to chapters like the the Mortifactors, who have had contact with the Ultramarines for 10,000 years and clashed quite heavily. Of course that could be just GW contridicting themselves again.

starlight
22-08-2010, 14:55
14,000...that we *know* of... :shifty: After all, we're taking about the only Chapter who was able to have an entire Chapter created to do their bidding... :shifty: ...and one who isn't known to suffer Inquisitorial oversight gladly... :shifty:


As for the Ultramarines, as of the current Codex Calgar can call on the Chapter Masters of his Successor Chapters, and given the new *everyone wants to be like Marneus* theme, they'll all come a' runnin... :shifty:


Not that I agree with that theme as a good thing, but it's there nonetheless. :( And given the Fleet and IG-equivalent assets the Ultramarines command... :shifty: Let's just say it's a pretty big power base...

Lord_Crull
22-08-2010, 15:03
14,000...that we *know* of... :shifty: After all, we're taking about the only Chapter who was able to have an entire Chapter created to do their bidding... :shifty: ...and one who isn't known to suffer Inquisitorial oversight gladly... :shifty:


Not really, creating a chapter is not an easy thing to do. Remember it's only the High Lords who can effectively raise new chapters.



As for the Ultramarines, as of the current Codex Calgar can call on the Chapter Masters of his Successor Chapters, and given the new *everyone wants to be like Marneus* theme, they'll all come a' runnin... :shifty:


Not really. The Codex uses the term ''aid'' and makes it sound more like a self-defense pact than anything else. If Calgar has the power we certainly have not seen him use it. Even in the Balur Crusade Calgar went to war with just elements of six chapters one of which was the Black Templars and no Ultramarine sucessors showed up for Behemoth.



Not that I agree with that theme as a good thing, but it's there nonetheless. :( And given the Fleet and IG-equivalent assets the Ultramarines command...

Fleet and IG assets? Ultramar has the Ultramarines chapter fleet and a rather limited self-defense fleet as seen in Chapter's Due. It's hardly a comparison to the actual Segmentum Fleets. And calling the Ultramar PDF ''IG-equivalent'' is rather dubious considering most IG regiments would have vastly more experiance


Let's just say it's a pretty big power base...

Not really, first of all the Ultramarines control a grand total of eight system (eight planets really) that's utterly insignifcant compared to a Segmentum, let alone the Imperium as a whole. The PDF and Defense fleet are not quite up to the levels of the actual Navy and Guard IMO (Of course for the Guard that is hard to qualify since we have such varying degress of competence and equipment)

As for the rest of the chapters.......actually getting them into play would be a massive feat given the difficulties of communication and travel between the chapters. Plus we have Chapters like the Mortifactors who don't answer Calgar as their spiritual leige but are Second Founding Ultramarines.

Given that the Chapters have homeworlds and places of the galaxy of their own to defend, plus the difficulties of communication and travel........only a very small percentage would be able to answer Calgar if needed. It would take a long time and be highly impractical to gather them all.

MagosHereticus
22-08-2010, 15:40
for the record, codex chapters dont deserve a bonus on their boarding action rolls in bfg

geeksquared
22-08-2010, 18:14
Can someone tell me where the untrlmarine get all these extra guys? I follow the black library books and play a lot of dark heresy but I gave up on playing 40K a while ago in favour of specialist games like Necromunda and Blood Bowl. The last SM codex I read was the 3rd ed Space Marine Codex which said that the Codex Astartes gives a full chapter as 1000 battle brothers.
Every bit of fluff I've read regarding the Ultramarines stresses that they follow the dictates of the Codex TO THE LETTER. Its like their holy text. So where did this 'Ultramarines are 20,000 strong' thing come from? is it space marine fanboys or GW contradicting themselves again (one of the reasons I stopped playing).

jb85
22-08-2010, 18:55
Not really. The Codex uses the term ''aid'' and makes it sound more like a self-defense pact than anything else. If Calgar has the power we certainly have not seen him use it. Even in the Balur Crusade Calgar went to war with just elements of six chapters one of which was the Black Templars and no Ultramarine sucessors showed up for Behemoth.

That is a very good point in relation to Calgar being able to exert significant influence over sucessor Chapters. In one of the Ultramarines darkest hours, dozens of sucessor Chapters did not rush to Ultramar in its defence, the only aid came from the Imperial Navy fleet at Bakka. In addition, in the subsequent clean-up operations, it was Dante and the Blood Angels that provided the Ultramarines with support.

starlight
22-08-2010, 22:15
Of course this was also:

a) to paint a picture of extreme heroism in the face of overwhelming odds
and
b) well before the current *Codex:Ultramarines* flavour being pushed.


It wouldn't be so great a tale if it was really the combined First Companies of a dozen or so Ultramarine Successors having what amounts to a live fire exercise... :shifty: ...and it was at a different point in the timeline of GW...

massey
23-08-2010, 03:35
Can someone tell me where the untrlmarine get all these extra guys? I follow the black library books and play a lot of dark heresy but I gave up on playing 40K a while ago in favour of specialist games like Necromunda and Blood Bowl. The last SM codex I read was the 3rd ed Space Marine Codex which said that the Codex Astartes gives a full chapter as 1000 battle brothers.
Every bit of fluff I've read regarding the Ultramarines stresses that they follow the dictates of the Codex TO THE LETTER. Its like their holy text. So where did this 'Ultramarines are 20,000 strong' thing come from? is it space marine fanboys or GW contradicting themselves again (one of the reasons I stopped playing).

Perhaps you should reread the thread. The general consensus is that chapters have about 1000 marines. This, however, does not include guys like Techmarines, Chaplains, Apothecaries, various officers, people who hold certain ceremonial duties, etc. In fact, the codex specifically allows for these positions to not count against the 1000 number. It also does not include scouts.

So this means that the Ultramarines, devout followers of the codex, can have over 1000 marines and still be perfectly within the rules. Yes, it's their holy text. But you'd better believe that they know exactly what is within the rules. They wrote the book, after all.

I once got into an religious argument with a guy. He was a know-it-all and berated me and several others for believing our silly little faiths. He brought up the subject of Purgatory, and when we didn't defend the idea, he mocked us for not even understanding or following our own religion. Then I had to point out that I'm a Baptist, and Baptists don't believe in Purgatory. He also made a big deal about the fact that Christians don't follow the Old Testament dietary restrictions (no eating pork, etc). Someone else then pointed out that there's a line (I forget where) that is interpreted as lifting those dietary restrictions. I'm not sure what his concept of Christianity was, but he didn't understand that even extremely religious people can have very nuanced interpretations of their holy book.

To apply this to the Ultramarines, sure they follow their holy book, but the idea of only 1000 marines is a gross simplification. They take the codex very seriously, but that doesn't mean that they follow the 1000 men restriction to the exclusion of all else. I'm sure if you sat down and had a conversation with an Ultramarine, he could give you a very eloquent and well thought out explanation on exactly how that restriction applies. He'd be very serious and would believe that they are following the codex to the letter. What it boils down to is that the codex allows for more men and more flexibility than you give it credit for.

The 20,000 number that you reference was people talking about the Ultramarines calling upon their successor chapters. The current Space Marine book mentions that the Ultramarines maintain very good relations with many of their successors, and often fight alongside them. What that means is that Marneus Calgar can effectively command a mini-Space Marine Legion. He calls up, say, the Black Consuls, the Sons of Orar, the Novamarines, the Howling Griffins, the Silver Skulls and the Eagle Warriors, and if they are available, they will show up. Since Calgar is the commander of the Ultramarines, he will take overall command of the task force. That is where people get the larger numbers. I think the relationships are probably less formalized than, say, the Dark Angels, who seem to still be a Legion in all but name.