Editing First Founding (section)

==Organization==
[[File:Space Marine Legion.jpg|400px|thumbnail|right|]]
The Legiones Astartes, being far larger than current Space Marine Chapters, were organized along drastically different lines. At the head of the Legion was its [[Primarch]] Commander who oversaw the Legion's headquarters. Prior to reuniting with their Primarch, this position was filled by the Legion Master, the most senior Space Marine in the Legion. Below this were the '''[[Space Marine Chapter|Chapters]]''' of the Legion, each of which was commanded by a [[Chapter Master|Lord Commander]]. Each [[Space Marine Chapter|Chapter]] in turn was divided into a number of '''Battalions''' led by a '''Lieutenant Commander'''. Each battalion was then further divided into '''Companies''' led by a [[Brother-Captain|Captain]]. The Company, itself divided into a number of '''Squads''', was the basic military division of the Legiones Astartes. Due to the varying sizes of each Legion and the varying nature of supply and attrition, there was no fixed number of how many Chapters, Battalions, Companies, and Squads a Legion would contain. But even then, there was no fixed [[Codex Astartes|institution]] that a particular Company should be composed of certain units, with each Company specialising naturally as marines and officers became veterans of a certain form of warfare.

===Number of Legionaries===
The Legions were massive armies, and the size of each could vary tremendously. A precise number was never truly achieved and maintained. Even during the Great Crusade, some Legions were very numerous, while others were not. The numbers would always vary with new recruits and inevitable battle-losses, and also important was the availability of potential recruits and the [[Roboute Guilliman|administrative]] [[Perturabo|skills]] of the Primarch and his officers.

However the closest thing to a 'standard' legion is what the Emperor started with which was 10 chapters to a legion, 2 battalions to a chapter, five companies to a battalion and 100 marines to a company. Theoretical nominal strength: 10,000.

The most numerous Legion of all was the [[Ultramarines]]. The [[Thousand Sons]] of [[Magnus]] were of a small number as many of them had developed mutations or uncontrollable levels of psychic powers. [[Fulgrim]]'s samples had been largely lost, and this left the Legion of the [[Emperor's Children]] also with a very small number. Both of these Legions would increase their numbers to acceptable standards only after their Primarchs were found. The [[Dark Angels]], being the First Legion, were originally the largest one but their numbers declined significantly during the [[Rangdan Xenocides]]. The Iron Warriors were also quite numerous for a while, but Perturabo's [[Death Korps of Krieg|unique view on what qualified as acceptable losses]] changes that in time.

The approximate sizes of a few of the Legions at the start of the Heresy have been given in various sources (it should be noted that originally these numbers were much smaller, a full zero knocked off until they were upped by the BL/Forgeworld writers):

*[[Dark Angels]] - 200,000 or just above, though it is uncertain whether this includes Luther's contingents of the Fallen. Recent Horus Heresy era fluff would seem to suggest that it does not.
*[[Emperor's Children]] - 110,000 before the Isstvan Atrocity
*[[Iron Warriors]] - 150,000 to 180,000 but could have been more, if not for them regularly taking horrific casualties. The estimate is from after the notably costly series of wars that preceded their betrayal, suggesting higher numbers in the past.
*[[White Scars]] - 95,000 (Horus Heresy III: Extermination states they had 800 pioneer companies [[Derp|of as few as 500 marines each]], implying they had [[What|400 000 marines]], but [[Fail|this can probably be discounted]])
*[[Space Wolves]] - 90,000 to 95,000, with 75,000 gathered for Prospero and 20,000 to 25,000 elsewhere
*[[Imperial Fists]] - 100,000, the 20,000 at Phall were said to be 1/5 of the Legion
*[[Night Lords]] - Officially 90,000 to 120,000 but conceivably comparable to the larger Legions at points during the Horus Heresy. One of the most difficult legion sizes to estimate.
*[[Blood Angels]] - 150,000 divided in 300 companies 500 strong. Does not include the small caretaker force of a few additional companies constantly maintained on Baal.
*[[Iron Hands]] - 113,000
*[[World Eaters]] - 150,000
*[[Ultramarines]] - Black Books explicitly say they're the largest Legion at some 250,000 strong. To no-ones surprise Guilliman kept good records so this number is pretty safe.
*[[Death Guard]] - 95,000 (Mortarion wanted a much larger Legion but never came close to attaining it).
*[[Thousand Sons]] - Originally around or under 10,000, retconned to have 80,000 to 85,000.
*[[Sons of Horus]] - 130,000 to 170,000, 70,000 to 110,000 after Isstvan III
*[[Word Bearers]] - 140,000 to 250,000+, their official and explicitly incorrect size was 140K and we don't know who what extent they grew in secret after their shaming at Khur.
*[[Salamanders]] - 89,000
*[[Raven Guard]] - 84,000
*[[Alpha Legion]] - In-universe speculation is 90,000 to 120,000, with 180,000 probably being the greatest probable size. No-one knows for sure.

Using the lowest and highest numbers this means there were 1,933,095 to 2,741,000 Space Marines without including the White Scars. These estimations are the Legions at the closing of the Great Crusade, though it would be a mistake to assume that the number was final and only went down during the Horus Heresy. In fact, many of the Legions were still recruiting at an accelerated rate and their numbers actually went up, [[Raven_Guard#The_Last_Ones_Standing|though at some cost however]]. To put some context to that number, on the low end that's about the size of the American forces in the Korean War, and on the high end that's about all the Soviets that were involved in the Battle of Berlin.

It's also a mistake to assume that the Traitor Legions went turncoat completely en-masse, when in fact the [[Traitor Legion Loyalists|Loyalist elements of those Legions]] counted for a significant portion of their strength. Approximately 100,000 loyalist Legionaries were purged at Isstvan III, practically counting for a Legion-sized force to themselves. Their destruction came at a much greater cost to the Traitor Legions mustered there, cutting the traitor forces down by half, probably more, and so Horus would enter the war with his strength greatly reduced, but could count on daemon auxiliaries for reinforcements, the almost complete annihilation of three Loyalist legions during the [[Drop Site Massacre]] also helped to even out the field between both sides. While rare, there were also a few members of loyalist Legions who sided with the traitors as well - the Dark Angels and White Scars in particular were very nearly torn apart by the resulting infighting. The White Scars only reunited after Jaghatai Khan revealed what he had learned and made the Horus supporters surrender, after which some of the worst offenders were executed and the rest were placed in the most dangerous warzones to redeem themselves. The Dark Angels actually split more dramatically, though their detractors were more inward-looking and can't be seen as aligned with Horus. See their own article for more details.

===Assets===
Besides having far greater numbers of Astartes to draw on, the legions were also better equipped and had a much wider variety of arms and vehicles to choose from. Many armored vehicles that are currently Imperial Guard specific once served in the legions, such as the [[Basilisk Artillery Gun|Basilisk]], while other wargear like [[Volkite]] guns or [[Mastodon]]s were mothballed due to their rarity or their obsolescence for the smaller-sized chapters. Numerous tactical roles were likewise phased out, for better or worse, though some roles did find successors in contemporary Chapters both Astartes and [[Primaris Marine|Primaris]].

'''Heresy-Era Specialties:'''
*[[Breacher Siege Squad]]
*[[Despoiler Squad]]
*[[Destroyer Squad]]
*[[Moritat]]
*[[Reconnaissance Squad]], succeeded by [[Scout Squad|Scouts]], [[Infiltrator]]s and [[Eliminator]]s.
*[[Seeker Squad]]
*[[Sky Hunter Squad]]
*[[Tactical Support Squad]]
*[[Legion Consul]], succeeded by [[Chaplain]] and [[Judiciar]].
*[[Master of the Signal]]
*[[Legion Herald]], succeeded by Ancient and [[Primaris Ancient]].
*[[Praetor (Space Marine)|Praetor]], became the [[Chapter Master]] role.
*[[Legion Vigilator]], succeeded by Scouts and Eliminators as well.
*Various other [[Consul]] roles