Editing First Founding (section)

==Legions in 40k==
Technically all of the Chaos Marines are still 'legions', at least in name. They never split into chapters, so legions they technically remain. However, since they are mostly split up into roving warbands and there is no central control ([[Black Legion|with]] [[Word Bearers|a]] [[Death Guard|few]] [[Thousand Sons|exceptions]]) it's hard to say they really count anymore. Perhaps most importantly it's impossible to guess how many dudes there are even technically in any legion's pool. When they aren't fighting the Imperium, they are fighting each other, and since none of the Black Crusades have been successful we can reasonably assume that Chaos Marines aren't pouring out of the Eye of Terror in their hundreds of thousands. It's utterly impossible to guess how many dudes they've got. They obviously have enough to attack the Imperium with (especially since their recruiting practices aren't as picky as their Loyalist counterparts), but probably not much more than the Loyalist Space Marines. Probably more than they came to the Eye with though, between further recruiting (from the Eye of Terror human population and anyone they can abduct/brainwash) and former Loyalists turning to Chaos.

As for the Loyalists... Since the introduction of the [[Codex Astartes]], there are obviously no longer any loyalist Space Marine legions though that does not stop certain chapters from being described or implied to be at ''"Legion Strength"''. Though this is often a common [[Neckbeard]] error and sometimes even gets used in the fluff, where the term is mistakenly used to describe any significantly oversized chapter, though even then they never compare to the forces from the Great Crusade. Though some make a good attempt at it:
 
*[[Imperial Fists]] - As it turned out, Dorn didn't fully break up his Legion. Every Son of Dorn chapter has a secret plan dubbed "The Last Wall"- if the main Chapter were to encounter an immediate threat to Terra, it could call its successor chapters to unite them into a full Legion until the threat is dealt with; the prospect of so many chapters working in such close cooperation was something that frightened the [[High Lords of Terra]] and they did not approve. Nonetheless, this plan not only saved Terra from [[The War of The Beast|the largest Ork WAAAGH!! the Imperium has ever dealt with]], but also rescued the Imperial Fists from ''actual'' extinction in the process.
*[[Black Templars]] are obviously over-strength in multiples of 1000 and keep to the spirit of the Great Crusade unlike any other chapter. This force is made up of three primary crusade fleets of unknown size which can end up spread over up to thirty engagements, where the size of a force could be as large as [[Dawn of War|"nearly" chapter strength]] ''(but not '''over''' for obvious reasons)'' or as small as a [[Dawn of War 2|single ship and a handful of squads]], so can be averaged at around chapter strength for each primary fleet. This arrangement is meant to be fluid, and changes all the time as fleets merge and disperse. Respectable figures put their numbers between 2000-6000 (with some more recent sources claiming even as high as 25000). The Templars are able to get away with this due to an obscure exception in the Codex allowing chapters to be over-strength during major Crusades in order to easily replace losses, and the Templars are ''always'' crusading. This is unofficially tolerated by the High Lords because of fanatical loyalty, constant casualties, consistent results and the fact that the Templars are so spread out. They may be legion sized 'total' but they're not Legion sized at any single location.
*[[Space Wolves]] make no secret of the fact they ignore the Codex Astartes, but even then they are no-where near their original size. In M32 during the '''Battle of the Fang''' it is remarked that most of ''The Aett'' is actually abandoned. Furthermore, Logan Grimnar's own Great Company numbers 200 marines prior to the Sanctus Reach campaign and is the largest company on its own ''(i.e.: not including the chapter assets)''. Their current number was originally between 1200-3000, but following the Siege of Fenris it is almost certainly smaller. Though the influx of Primaris Marines they received shortly afterwards likely also replenished their losses, and perhaps even surpassed their original numbers. Vikings aren't exactly renowned as avid number-keepers at the best of times though, so who the hell knows (though it is almost certain it is above official chapter strength).
*[[Astral Claws]] were ''actually'' accused of Legion building and declared heretics even when they were not yet followers of [[Chaos]], their number at the time of the Badab War was around 3000, though they never even used that number as a single force and spread themselves throughout their '''[[Warhammer_40,000/6th_Edition_Tactics/Tyrant%27s_Legion|PDF forces]]'''.
*[[Dark Angels#The Unforgiven|The Unforgiven]] are most likely one of the closest examples of a true Legion in that each of the successor chapters arrange themselves under one ''secret'' command structure (the '''Inner Circle'''). Though they each [[RAW|obey the letter, if not the spirit]] of the [[Codex Astartes]] and maintain mostly standard chapters of ten companies. The combined numbers of Dark Angel's successors would put them at around ''150,000 marines'', and this is just a rough estimate, though we don't know if all of the Dark Angel's successors actually consider themselves part of the Unforgiven. Some definitely do though. Oh yes indeed. The Inner Circle has been known to send a random successor chapter across the galaxy to do the space marine equivalent of getting them a six pack (of traitors) when the main chapter is too busy.
*[[Ultramarines]] - The 23 [[Second Founding]] chapters of the Ultramarines are all represented in the senate of [[Ultramar]] and some of them would cooperate on matters of Codex orthodoxy to ensure that there were no deviations. The [[Genesis Chapter]] in particular routinely loaned squads and officers to the Ultramarines to fill in gaps, while other successors could loan squads to the [[Ultramarines Honour Company]] and get to wear the blue uniform. Because the Ultramarines account for nearly half of the later-founded chapters in the Imperium, they would amount to around ''500,000 marines'' and nominally look to their progenitor for the source of their leadership and guidance, with instances of Marneus Calgar stepping in to settle disputes between chapters not even of his bloodline or issuing decrees against [[Minotaurs|chapters]] in matters that have nothing to do with the Ultramarines directly. With the return of [[Roboute Guilliman]] and his re-organisation of both the Codex and the region of Ultramar; even though chapters officially maintain their sovereignty apart from each other, he has formally created a cross-Chapter command structure of Tetrarchs to coordinate and protect the Five-Hundred Worlds.

All of the original legions maintain ties with with their subsequent founding chapters (except for the Salamanders, who didn't have any confirmed successors until the Ultima Founding, and ignore the unconfirmed ones), though the level of formality is different from Chapter to Chapter. The Blood Angels occasionally call all their bros together and go to war, even going to far as to demand they provide the Blood Angels with new squads so that they could rebuild their weakened chapter, but even in those cases, [[Gabriel Seth]] had to remind [[Dante]] that he had no authority to actually demand troops from his successors and might get further by asking nicely.

The Imperial Fists successors did the same thing during the War of the Beast by donning Imperial Fist colours to ensure that the Chapter would not go extinct after it was nearly wiped out. The new Imperial Fists considered changing their colours controversial and a little bit blasphemous, and the [[High Lords of Terra]] generally weren't happy about that many Space Marines working in such close cooperation at all.

While musing with Aeonid Thiel, Guilliman's original dream for the Codex was not to split up the Legions at all, but to create a single unified Legion formed of self-sufficient chapters that would come together or break apart as necessary, irrespective of their individual bloodlines, while making it harder for a taint in one chapter to affect the whole.

Given the number of times multiple chapters from different legions have gotten together for a big crusade, he arguably succeed in this goal. Much of what goes on with the Ultramarines tended to be done out of starry-eyed respect and deference towards them rather than grudging support, so in this case, their high level of cooperation appears to be following the spirit of Guilliman's original idea quite well.

Obviously, the High Lords would prefer to think otherwise because they were scared to death of the possibility of a second Space Marine unification and uprising, even going so far as to plotting to overthrow the resurrected Lord Guilliman before he took control over the Senatorum (which instantly backfired when the Custodians got wind of it in about ten minutes, also you know, '''PRIMARCH''').