Space Marine Legions

"Alone, a Legionary is a formidable foe as far beyond a man as the wolf is beyond the sheep. Together, bound by ties of unshakeable loyalty, a Legion is a force that can extinguish the stars and shake the very heavens."

— Attributed to Lorgar Aurelian, primarch of the Word Bearers Legion

Legiones Astartes (Space Marine Legions)
Race	Mankind
Headquarters	Space Marine Legion homeworlds across the Milky Way galaxy
Government	Imperium of Man
Leader	Primarchs of each Legion
Military Forces	Twenty Legiones Astartes
Establishment	First Founding (ca.700.M30)

The Space Marine Legions, or the Legiones Astartes in High Gothic, were the original unit formations of the Firstborn Space Marines created during the First Founding by the Emperor of Mankind on Terra in ca. 700.M30.

This initial Founding happened before the start of the Great Crusade that reunited the scattered worlds of Humanity beneath the banner of the Imperium of Man, while the Unification Wars were still raging on Terra. Unlike the current Adeptus Astartes, who serve the Imperium of the 41st Millennium primarily as a planetary assault and rapid strike force, the Space Marine Legions were the primary frontline military forces of the ancient Imperium of Man, responsible for frontline combat in most military engagements, with the Imperial Army serving as auxiliary support and garrison troops.

This operational role changed after the Second Founding during the Time of Rebirth of the 31st Millennium, when the Astra Militarum replaced the Legiones Astartes as the Imperium's frontline armed forces, relegating the now-much smaller Space Marine formations known as "Chapters" to a more elite role. Their primary tactical specialties at present include force-multiplying special operations deployments, ship-to-ship combat and boarding operations, command and control decapitation strikes and planetary assaults.

Legiones Astartes

The I^st Legion, later called the "Dark Angels", assembled and awaiting departure for the Great Crusade.

A Space Marine Legion was a frontline force of shock-infantry comprising tens of thousands of transhuman Astartes warriors armed and equipped with the finest wargear the Imperium could supply. A Space Marine Legion, unlike the 1,000-man Chapters of the present-day Adeptus Astartes created after the Second Founding following the Horus Heresy, could number anywhere from 10,000 to more than 250,000 Space Marines, as well as the Legion's associated Imperial Army, logistical support forces and Armada Imperialis fleet elements.

A force of a hundred of these genetically and biochemically-enhanced transhuman warriors could quell a rebellious city in solar hours. Thousands could conquer an entire world in only solar days, and tens of thousands or even hundreds of thousands wielded at once were the doom of entire spacefaring species, capable of reducing alien civilisations to mere dust and memory in a span no greater than the single course of Terra's orbit around Sol.

Founded amid the bloodshed of the Unification Wars of Terra that swept the Emperor of Mankind to dominion over the cradle of Humanity in the 30th Millennium, the original military formation of the Legions was the division of twenty numbered units of genetically enhanced warriors, organised very much along the lines of the Thunder Regiments that proceeded them in the Emperor's service and who they would eventually replace.

Much of the discipline and organisation of the early Legiones Astartes owed greatly to the ancient and proven Terran patterns of military strategy, hierarchy and functions as laid down in the revered texts of the Principia Belicosa of Roma and Krom's (Oliver Cromwell) fragmentary "New Model" that had survived in the hands of the tyrants of Old Earth down the blood-stained generations of the Age of Strife.

To these venerable treatises the Emperor and His commanders had added their own genius and created a sturdy but adaptable strategic framework that spoke to the fundamental strengths and superhuman abilities of the Astartes themselves. At the outset of the Great Crusade in ca. 798.M30, many of these early Legions were raised along the so-called "Terran Pattern" of tactical organisation as formulated by the Imperium's Officio Militaris.

Of the twenty original Space Marine Legions, eighteen would survive to grow into vast forces by the end of the Great Crusade in the early 31st Millennium; as for those that did not (the II^nd and XI^th Legions), nothing can be said of their fate in current Imperial records.

Nine of these Legions would continue to stay utterly loyal and faithful to the Emperor during the Horus Heresy and thus they serve as the genetic forbears of all current Loyalist Space Marine Chapters of the present era. The Space Marine Legions and their primarchs were the Emperor's primary military force and most important advisers, respectively, and were intended to be the political and military speartip of the Great Crusade.

However, the Emperor also wanted to create a civilian government for the Imperium which would ultimately hold authority over even the primarchs, a change embodied in the creation of the Council of Terra in the early 31st Millennium that angered many of the Emperor's gene-sons and ultimately became one of the contributing factors to the outbreak of the Horus Heresy.

Sons of Horus Astartes infantry in Mark III Iron Power Armour armed with boltguns move forward during the final days of the Great Crusade supported by a Deredeo Pattern Dreadnought and Land Raider Proteus.

The Legions were aided by the combined ground and naval forces of the Imperial Army, the predecessor of the present-day Astra Militarum and Navis Imperialis, but these usually unaugmented Human forces more often served in support and garrison duties while the heaviest combat and the most important and difficult missions were always carried out by the Legiones Astartes.

As the Great Crusade continued the expansion of the nascent Imperium into the galaxy, the re-discovery of the primarchs and their newly adopted homeworlds helped to stem an impending crisis that was not widely known at the time outside of the exalted ranks of the Imperium's ruling War Council: namely, the diminishing stability of the Astartes gene-seed itself through over-use and the increasing need for more Space Marines in the field.

This was a matter that only worsened as the Great Crusade pushed ever wider afield into the galaxy. Imperial forces could no longer be concentrated as easily as before, and attrition was taking its toll as standard years of near-constant battle became solar decades. To slow the relentless pace of the Great Crusade's progress and the reunification of Humanity was for the Emperor simply not an option. As such, the simple truth was that more Space Marines were needed and they needed to be created faster than before.

In the later solar decades of the Great Crusade a secret conclave of gene-wrights under the Emperor's direct supervision posited the solution to the Legions' manpower needs that became known as Grabiya's Theorem, which demonstrated that a sample of a primarch's genetic code could be used to stabilise and expand the Astartes gene-seed stocks created from his template with what was hoped to be "minimal deviation".

Alongside this accelerated gene-culturing technique, other previously unavailable genetic technologies were put into effect, reducing the processing time required to create a battle-worthy Space Marine to as little as a single Terran year in some extreme cases. Such accelerated gene-seed techniques, along with absent, inadequate or over-forceful hypno-indoctrination techniques, were later found to have unseen fundamental flaws. Many Imperial scholars since have come to believe that the drive to create larger Space Marine Legions at an accelerated speed played a prime role in the degradation of the sanity and psychological make-up of certain Legions and paved the way for the horror that was to come.

A Salamanders Legion force deployed during the Horus Heresy including Leviathan Siege Dreadnoughts and Astartes infantry in Mark III Iron Power Armour.

Nine of the twenty original Space Marine Legions chose to follow the Warmaster Horus Lupercal and pledge their lives and service to his rebellion and later Chaos. They became the Traitor Legions of Chaos Space Marines that still threaten the Imperium today.

In the end, the Horus Heresy made clear that no single commander could be trusted to wield the enormous power of a Space Marine Legion, never mind several at once. The Ultramarines' primarch Roboute Guilliman led the post-Heresy reformation of the Imperium during the Time of Rebirth that reshaped the Legiones Astartes into the Adeptus Astartes and broke up each of the remaining Loyalist Space Marine Legions into the myriad 1,000-man Space Marine Chapters to protect Humanity from the potential rise of another Horus.

The remaining two Legions and their primarchs raised during the First Founding were lost to the Imperium some time before the Horus Heresy, with no trace of them remaining. It has been suggested that they were destroyed by, or under direct order of, the Emperor for some unknown, grave transgression, or flaw in their gene-stock, and all evidence of their existence was entirely purged from Imperial records.

Legion Size

A force of the Sons of Horus during the Horus Heresy accompanied by Mastodons, two Warlord-class and one Reaver-class Titan.

The Space Marine Legions were massive armies, and the size of each could vary tremendously. A precise, pre-set formation was never truly achieved or maintained. Even during the Great Crusade some Legions were very large, while others were not. The size of each Legion was fluid, with the numbers of combat-ready Astartes dependent on the number of new recruits, the inevitable battle-losses, the availability of potential recruits, and the administrative skills of the Legion's commanding primarch and his officers.

The largest of all the Space Marine Legions at the time of the Horus Heresy's start was the Ultramarines, followed by the Word Bearers. The Ultramarines numbered approximately 250,000 Astartes at their peak before the Battle of Calth and the Word Bearers approximately 100,000. It was the Ultramarines' sheer size, as well as the purity and stability of their gene-seed, which insured that more Second Founding Successor Chapters were created from the XIII Legion than from any of the other Loyalist Legions.

The Thousand Sons Legion of Magnus the Red was most likely the smallest of the Astartes Legions as many of the Space Marines within its ranks had developed rampant mutations or uncontrollable levels of psychic power and had to be granted the Emperor's Peace. The primarch Fulgrim's gene-seed stores had been largely lost on Terra due to an accident and viral contamination, making it difficult to develop new gene-seed for his III Legion, and this meant that the Emperor's Children found it difficult to recruit new Astartes, also leaving it with a relatively small number of Space Marines. Both of these Legions would increase their numbers to acceptable levels only after their primarchs were found by the Emperor during the course of the Great Crusade.

Other estimates exist, though all such numbers are always hard to pin down. Certainly the Legions were large, as they were responsible for the ultimate conquest of Terra during the Unification Wars and later for countless star systems and Human-settled worlds during the Great Crusade.

The Space Marine Legions that set off from Terra in the early days of the Great Crusade numbered at least 100,000 each, far larger than the 1,000 warrior Chapters of the 41st Millennium. But that alone was still not enough for the task of subduing a galaxy. In this optimistic era of reconquest for the newborn Imperium, Space Marines were rarely deployed to a combat theatre alone. They were the tip of Humanity's reforged spear, the shock troops who shattered the resolve of enemy empires, crushed xenos tyrants and blazed a trail for the more numerous but slower forces of the millions-strong Imperial Army.

As the Legions were slowly reunited with their primarchs, their composition changed, including their overall numbers. Some grew swiftly, while others favoured a more compact organisation -- and they all came to reflect the cultures of their adoptive homeworlds and the preferences of their gene-fathers. Some of these changes in size were well-recorded, while others were only ever estimated. With many Legions fighting across multiple warfronts, and recruitment largely their own specific purview, no single source can be 100% accurate.

Some Legions stuck rigidly to their original structure, like the Imperial Fists, ever keen to uphold the Emperor's original vision for a new Human golden age.

Others were known to have grown significantly. The Ultramarines were much larger than the other Legions by the time the Horus Heresy broke out in 005.M31, while the Sons of Horus and Word Bearers were also numerous. The Iron Warriors rivalled the Ultramarines in size, with pre-Heresy estimates putting that Legion at as much as 180,000 warriors.

Many Legions were smaller as much as the result of attrition as any logistical choice. The Thousand Sons and Space Wolves had tumultuous histories even before the Horus Heresy, and both were reduced further by their tragic conflict engineered by the machinations of the Warmaster Horus at the Burning of Prospero. The Space Wolves deployed 75,000 troops to this battle, yet only a third of that number survived by the time the Prospero fell -- where that left their overall strength, however, is anyone's guess. The Thousand Sons fared even worse, though no Imperial record can truly say how many escaped the wrath of Leman Russ.

The Dark Angels entered the Heresy in reduced numbers after a bruising campaign against the xenos Rangda during the Rangdan Xenocides. These bloody battles of extermination laid low almost an entire Legion's worth of Space Marines, a good number of them the gene-sons of Lion El'Jonson.

The size of some Legions can only be guessed at. No truly definitive Imperial records exist of the White Scars, Night Lords, or Alpha Legion*, though Imperial historitors know that at least 50,000 of Alpharius' gene-sons were present at the Drop Site Massacre on Isstvan V.

Traitor numbers at the start of the Horus Heresy are harder to be sure of, as most had undergone a period of "purging" Imperial Loyalists from their ranks. The Death Guard numbered around 95,000 by the end of the Great Crusade, for example, and are estimated to have culled about a quarter of their strength during the Battle of Isstvan III. The World Eaters, Sons of Horus and Emperor's Children were similarly purified of all potential dissenters.

A Salamanders Legion assault force makes a combat drop on the Urgall Depression of Isstvan V during the Drop Site Massacre. Present here is a Saturnine Dreadnought, as well as Astartes infantry and a squad of Saturnine Terminators as Drop Pods make planetfall in the background.

Many Legions shrank quickly in size as the brutal attrition of the Horus Heresy inter-Legion war began. None more so than the three Loyalist so-called "Shattered Legions" at the Drop Site Massacre. The Raven Guard and Salamanders deployed in almost full strength, and most were slain. The Iron Hands, meanwhile, were present in lesser numbers, but deployed their most elite companies, almost all of whom perished alongside their primarch. Despite this, all three of the Shattered Legions retained enough of their strength to become a thorn in the side of the Traitors even as they marched on Terra.

As the Horus Heresy ground on over the seven standard years following the Drop Site Massacre, many Legions accelerated their recruitment rates, struggling to match the constant rate of attrition, so brutal were the battles of the Age of Darkness. By the time of the Siege of Terra in 014.M31, most Legions had resorted to dangerously accelerated gene-seed implantation and indoctrination processes, swelling their ranks with thousands of untested but battle-hungry neophytes known as Inductii. These warriors were still Space Marines, but to them the glories of the Great Crusade were already only half-understood legend. They lived only to fight and die in a hate-filled civil war against other Space Marines.

By the time the Warmaster Horus Lupercal's Traitors reached Terra in 014.M31, hundreds of thousands, if not millions, of Legionaries, both fresh recruits and veterans, had fallen across the galaxy. Those Astartes who had served within a Legion prior to Horus' betrayal were now the minority, aged, veteran battle-brothers standing tall amid ranks who knew nothing but a Legion consumed by desperation or heretical corruption. Gone was the unity of a single Legion, for their numbers were scattered across the galaxy with varying adherence to Legion cultures and tactical disposition and specialties, each a pale imitation of an age of progress and hope now rendered extinct.

The approximate manpower available to several of the Space Marine Legions at the start of the Horus Heresy in the early 31st Millennium is recorded as follows, from largest Legion to smallest:

Legion Number	Legion	Prior Cognomen	Loyalty	Legion Strength
XIII	Ultramarines	War-Born	Loyalist	By 899.M30, the Ultramarines numbered around 166,000 Astartes, which stood them in the forefront of their peers. With the loss of 50,000 Legionaries sustained during the Third Rangdan Xenocide, the Dark Angels no longer secured primacy over their fellow Legions and had fallen in number and evened this figure. Following the dissolution and/or destruction of the II and XI Space Marine Legions, the ranks of the Ultramarines supposedly swelled to approximately 250,000 Astartes, making them the largest Legion at the start of the Horus Heresy.
I	Dark Angels	The First	Loyalist	Once the most numerous and powerful of the Space Marine Legions, conservative estimates placed the Dark Angels Legion at approximately 200,000 Legionaries at the beginning of the Great Crusade. Sadly, their numbers would be depleted and their primacy ended by solar decades of savage warfare, particularly in the wars of the Rangdan Xenocides, one of the most apocalyptic campaigns of the Great Crusade. They suffered massive casualties holding the line during the Third Rangdan Xenocide; the blood of 50,000 Space Marines was spent in preventing the destruction of perhaps the entire northern Imperium by the alien menace from the outer darkness.
XX	Alpha Legion	Ghost Legion	Traitor	Exact figures for the martial strength of the Alpha Legion at the outset of the wars of the Horus Heresy are impossible to obtain. Sources and estimates vary wildly, some making extravagant claims which may both overestimate or undervalue the Alpha Legion's manpower. Most contemporaneous accounts around the time of the Drop Site Massacre put the Alpha Legion at between 120,000 and 130,000 Astartes strong, placing it within the middle tier of Legion strengths. Some theorists have pointed the figure as far lower, somewhere in the 90,000 range based upon the largest concentration of Alpha Legion forces ever seen in operation in a single theatre. With hindsight and diligent corroboration however, evidence of multiple simultaneous battle-groups operating in far distant locales suggests a far higher figure than either of these estimates, well into the range of 180,000 Legionaries which, if accurate, would make it one of the most formidable Legions in sheer size alone, a factor unguessed by both sides of the interstellar civil war that was to follow.
IV	Iron Warriors	None	Traitor	At the time of the outbreak of the Horus Heresy, the Iron Warriors Legion is estimated to have had an active strength of between 150,000 and 180,000 Astartes, along with a very substantial war fleet of over a hundred capital class vessels. More accurate assessment than this is, however, impossible given the considerable portion of sub-deployments and garrisons that were maintained by the Legion scattered across the Imperium and its increasingly isolationist tendencies in the years before the civil war. It is believed that the Legion had further accelerated its indoctrination and recruiting program, as well as local shipbuilding at Olympia in the lead-up to the rebellion, and so the lower division of these estimates may indeed be erroneous.
XVI	Sons of Horus	Luna Wolves	Traitor	130,000-170,000 Astartes during the latter days of the Great Crusade; approximately 70,000-110,000 Legionaries following the losses sustained during the Isstvan III Atrocity. Heavily engaged on the surface of Istvaan III, it is estimated that some 30,000 of the Sons of Horus were dead or unaccounted for in the aftermath of that battle.[Note 1]
XII	World Eaters	War Hounds	Traitor	150,000 Astartes estimated at the XII Legion's peak. It is commonly estimated that of all the Legions that had fought at Istvaan III in the purge of the Loyalist faction within their ranks, it had been the World Eaters who had suffered the greatest casualties, with well over 35,000 World Eaters Legionaries believed to have met their deaths on both sides. Aside from the many wounded, it is recorded that a number had succumbed entirely during the protracted fighting to an insane bloodlust and had to be forcibly restrained and removed back to the World Eaters fleet for containment.
XVII	Word Bearers	Imperial Heralds	Traitor	Exact numbers unknown; approximately 140,000 Astartes at the time of the Drop Site Massacre, though following their rebukement at Khur, the XVII Legion had grown to far greater strength than was originally reported.
IX	Blood Angels	Revenant Legion	Loyalist	Approximately 120,000 Astartes estimated at the Legion's peak.
X	Iron Hands	Storm Walkers	Loyalist	In excess of 113,000 Astartes at the start of the Horus Heresy. Following the disaster of the Drop Site Massacre on Istvaan V, the X Legion was reduced to a mere shadow of its former strength. Exact estimates are unknown.
III	Emperor's Children	Unknown	Traitor	110,000 Astartes during the latter days of the Great Crusade; approximately 50,000 Traitor Legionaries survived the Istvaan III Atrocity. No reliable account exists of the fatalities suffered by the III Legion during the excision of its Loyalist elements on Istvaan III, but it is believed to have been proportionally very high.
VII	Imperial Fists	None	Loyalist	The strength of the Imperial Fists was never measured in large numbers. Though not small, their tallies of warriors during the Great Crusade never rose above 100,000 Astartes. At the time of the withdrawal to Terra, the Legion records show that the Temple held the majority of its living warriors, although such a number cannot be taken as accurate. The vagaries of Warp travel, Astropathic communication and the volume of space across which the Great Crusade was fought means that all that is certain is that this tally is nothing but plausible estimation.[Note 2]
VI	Space Wolves	None	Loyalist	At the time of the Great Crusade and the Horus Heresy, the VI Legion comprised approximately 95,000 to 100,000 Legionaries.
XIV	Death Guard	Dusk Raiders	Traitor	95,000 Astartes at its peak. With the conclusion of the bitter fighting on Istvaan III, it is estimated that the XIV Legion had been reduced by well over 25,000 casualties, counting both the stubborn Terran Loyalists, betrayed to their deaths in the ash-mantled ruins of Istvaan III's Choral City, and Mortarion's sons of Barbarus whose lives had been spent to purchase their demise.
XV	Thousand Sons	None	Traitor	Estimated total strength of perhaps 80,000-90,000 Legionaries at the time of the Fall of Prospero in 004.M31. 62,000 were present on Prospero by judgement of after-action reports (many of which are contradictory). Apocryphal sources state that approximately 1,242 Traitor Legionaries supposedly survived the massacre by the Space Wolves to escape to the Planet of the Sorcerers in the Eye of Terror.[Note 3]
XVIII	Salamanders	Dragon Warriors	Loyalist	Total number unknown; approximately 89,000 Astartes at the end of the Great Crusade. 83,000 Legionaries deployed with their Primarch Vulkan to Isstvan V. During the Drop Site Massacre, the XVIII Legion suffered nearly a total loss, rated by some sources as high as 98% of the Legion's Space Marine personnel. However, other detachments such as the garrison maintained at Geryon Deep and the Castellan of Prometheus' forces were comprised of about 2,000 to 3,000 total Astartes, alongside the full intake of Salamanders Neophytes in training on Prometheus. There also were several line companies of the Salamanders Legion on detached deployment elsewhere at the time of the Drop Site Massacre, leaving the total number of the XVIII Legion's effectives after the Drop Site Massacre unknown.
XIX	Raven Guard	None	Loyalist	When the Raven Guard committed to the Istvaan V drop, they did so in numbers approaching their full strength, just under 80,000 Legionaries, with all assets, both surface and spaceborne, in attendance. The Raven Guard were to lose nearly 75,000 Astartes during the betrayal known as the Istvaan V Drop Site Massacre, and by the end of the ninety-eight solar days that followed, could muster but a fraction of their former strength. Leaving aside these unknown numbers operating alone in the outer darkness, the Raven Guard barely numbered around 4,000 effectives, including those despatched to garrison Deliverance. For the first time in their glorious history the Raven Guard were truly laid low.
VIII	Night Lords	None	Traitor	At the time of the Drop Site Massacre, the Night Lords were estimated to comprise slightly over 90,000 Legionaries, though others put their number closer to 120,000 Astartes. Following their campaign against the Dark Angels in the Thramas Sector, their numbers had dwindled to an estimated 10,000 Legionaries. This reduced number comprised the VIII Legion during the remainder of the Horus Heresy.
V	White Scars	Star Hunters	Loyalist	The V Legion is believed to have comprised 95,000 Astartes at the end of the Great Crusade, making it one of the smaller Legions.

Notes on Size

The size of a Space Marine Legion has been a contentious issue over the years, with various numbers mentioned in multiple sources intended to reflect the notional size of a Space Marine Legion.

This matter is further complicated by the fact that the size of the different Legions may vary based on source material or an author's lack of background information, which can result in conflicting numbers.

In general, the canon for the size of the Space Marine Legions has been set at numbers in the low hundreds of thousands, using the work of Alan Bligh in The Horus Heresy series for Forge World as the definitive source.

Games Workshop lead games designer and author Andy Chambers addressed this issue about pre-Heresy organisation in White Dwarf 272, "GW Mailbox," stating, "There really isn't any information on pre-Heresy organisation. We work on the principle that Space Marines started out in Legions approximately 10,000 strong (or more, depending on the specific Legion), which were broken down into Chapter-sized Great Companies rather like the Space Wolves (who are renowned for not adopting the Codex Astartes alteration made by Guilliman post-Heresy and who thus probably follow the pre-Heresy organisation more closely)."

• Note 1: In the novel Dark Creed by Anthony Reynolds, before the invasion of the Boros Gate by the Word Bearers Traitor Legion in the 41st Millennium, it is mentioned that the Black Legion's strength is unparalleled, and that they easily outnumber the Word Bearers by almost 10-to-1. This means that if the Word Bearers had somehow managed to maintain their ranks around 100,000 Chaos Space Marines, this would imply that the Black Legion has vastly increased its overall size since the Horus Heresy, with a primacy of around 1 million Traitor Marines.

• Note 2: In the novella The Crimson Fist by John French, it is mentioned that the Imperial Fists' Retribution Fleet numbers around 20,000 Legionaries, which constitutes one-fifth of the entirety of the VII Legion. This makes their overall number stand at around 100,000 Astartes.

• Note 3: In the novel A Thousand Sons by Graham McNeill, it is stated at the conclusion of the Burning of Prospero that First Captain Ahzek Ahriman counts around 1,242 Legionaries present during this conflict, and states that this constitutes approximately one-tenth of the XV Legion, which would place the Thousands Sons at only around 10,000 Astartes at their prime. But according to the information within The Horus Heresy Book Seven: Inferno, released in February 2017, the estimated strength of the Thousand Sons stood at approximately 80,000-90,000 Legionaries, with 62,000 being present on Prospero. This source also goes on to state that some of the detachments fighting in the Great Crusade elsewhere in the Imperium were to be destroyed by their allies before news of Prospero's destruction reached them: 2,000 under Sentor Rahme of the 9th Fellowship were slaughtered in their encampments by the Ultramarines attached to the same force, and 300 Veterans of the 7th Fellowship were abandoned to their deaths during the assault on Maktor VIII by the Imperial Fists to name but two of the more prominent cases. Of all the main contingents of the Thousand Sons abroad in the galaxy, only two were known to have escaped Imperial justice, the majority of the 4th Fellowship, some 5,000 Astartes who fled their Great Crusade assignment after hearing of the Space Wolves' attack on Prospero, and a force, perhaps of several thousand, of the 6th Fellowship present on the Forge World of Zhao-Arkhad as part of the agreement between the XV Legion and that distant and enigmatic Mechanicum forge. All of this information has obviously been retconned from the original numbers for the XV Legion presented in the novel.

Legion Organisation

Strategic Disposition of a Space Marine Legion during the later Great Crusade

The smallest formation within the "Logos Terra Militia" and therefore within the early Space Marine Legions was the squad. This consisted of a group of Astartes under the command of a non-commissioned officer with the rank of sergeant.

Squads varied widely in both size and specialisation, with the majority of the units ranging between 10 to 20 Space Marines. Conversely, very specialised squads such as reconnaissance units or those that had suffered heavy casualties might only consist of a handful of Space Marines in active service.

The chain-of-command was simple and direct, and the Legions' officers, themselves mighty warriors, would lead their Astartes into battle personally as had long been the wont of the techno-barbarian tribes of Old Earth. The battle would always be taken to the enemy because to defeat a foe was never enough for the Legiones Astartes, only the utter destruction of an enemy of the Emperor counted as a victory.

This cold logic, coupled with their inhuman strength and bearing, and the sheer dread they inflicted on friend and enemy alike, was to give the Space Marines one of their earliest appellations, and perhaps their most appropriate -- "the Angels of Death". It would be a name they would earn time and time again.

Legion Integration and Development

The Legiones Astartes of the Great Crusade were a fusion of dual natures. They were the product of the Emperor's conquest of Terra and the Sol System. Selected from Terran stock and moulded by the final years of the Unification Wars fought to create the nascent Imperium, these Legions held a certain commonality of culture and character.

A sense of unity and an almost familial bond pervaded their ranks. Given that they were all of the first generation of Astartes, born of Terra, they shared the imprint of their genetic forging and warlike history, and it is no surprise that members of the early Legions regarded each other as siblings, as brothers-in-arms.

Training, hypno-indoctrination and the shared experience of battle on Old Earth and in the Sol System reinforced this belief within the Legiones Astartes, encouraging the idea that they were a family born in the cradle of war. This bond of brotherhood would survive as the Imperium grew, but perhaps it was never as strong as it was when the Legions first conquered the techno-barbarians under the Terran sun.

The second face of each Legion was that of the people and cultures which had flourished under different stars. As the war to unify Terra became a crusade to conquer and re-unify the Human-settled galaxy, the Legions grew. Casualties had to be replaced, and as the wars grew in scale so too did the number of losses and the number of recruits that were needed to take the places of the fallen.

Initially intakes were drawn from Luna, Saturn's orbital stations, the Proximal worlds, and dozens of other Human colony planets of the near Segmentum Solar fed the Legions' needs for warrior stock. As this occurred, the Terran foundations and character of each Legion became diluted but were never overwhelmed, for the warrior tribes and cultures of Old Earth were many and their commitment to the Great Crusade resolute.

With the re-discovery of the primarchs and in many cases newly adopted homeworlds used as Legion fiefs (most commonly the worlds upon which a Legion's new master had been found), this was to change the character of the Legions profoundly. Some alterations were superficial: a habit of speech, a change in close-quarter tactics, martial traditions and warranted additions to iconography and even language. But for others the change would prove dramatic, with entire paradigms of culture, tradition and even ideology overwriting what had come before, such as in what came to be known as the Space Wolves, Blood Angels and Dark Angels Legions.

In many cases the stamp of the Legions and the will of the primarchs on their recruits came to largely outweigh differences of birth or blood, but in other Legions such as the Luna Wolves and the Emperor's Children, a subtle divide would grow between those veterans who had been recruited into the ranks of the Astartes by the Emperor from Terra and those who had come into the Legion from their primarch's homeworld. This rift would be one factor among many that would lead several of the First Founding Legions towards ultimate damnation.

By the middle years of the Great Crusade the ongoing effects of these shifts within the Legions had resulted in a wide disparity in culture and organisation between them. The outward sign of this was the development of a distinct character which meant the original Terran military patterns they had adhered to at the outset of the Great Crusade had been largely abandoned or become so modified and diluted as to be in some cases unrecognisable.

There were, of course, exceptions in whole or in part, such as could be found within the Ultramarines and Iron Warriors Legions, who built upon rather than abandoned what had gone before, as well as those such as the White Scars to who the strictures and precepts laid out by the Officio Militaris of Terra were no longer even notionally applied.

There are those that have cited this increasing idiosyncrasy in hindsight as the seeds of division, of a sense of insularity and "otherness" growing between one Legion and another. This itself only fuelled rivalries and feuds that had begun to simmer beneath the surface of the Great Crusade, both between the primarchs and their Legions, that would later be exploited by Horus and his heretical conspiracy, and lay them open to the introduction of the Davinite warrior lodge cult structures into those Legions he favoured. These warrior lodges were the avenue by which the stain of the Warp would later taint those Legions that turned Traitor.

Legion Structure

By the time of the outbreak of inter-Legionary hostilities during the Isstvan III Atrocity in 005.M31, the command and organisational structure of a Space Marine Legion was often more a mirror of the character and preferences of its primarch and its abiding culture than formal writ.

While certain formations and features were common across the Legions as an outgrowth of practical manners such as deployment and logistics, their organisation and use was far from standardised. During the Great Crusade there were numerous terms for the internal constituent units of a Space Marine Legion, presented here from largest to smallest: "great companies", "regiments", "chapters", "battalions", "cohorts", "demi-chapters", "companies", "squads" and "maniples".

Most often, the practical reality of their disposition would vary still more as terminology used within different Legions for equivalent ranks and specialisations bore the mark of the Legion's character and culture rather than the desires of the Imperium's central administrators for a common military nomenclature.

In some cases this discrepancy increased as local languages and dialects such as Fenrisian or Khal'd had come to replace Imperial Terran (the forerunner of High Gothic). With these caveats in mind, the Strategic Disposition of a Space Marine Legion chart above describes the broad and most common structural basis of a Space Marine Legion (as well as some of the more commonly used terminology of rank) in the latter half of the Great Crusade.

Generic Space Marine Legion Order of Battle

By the time of the middle years of the Great Crusade, there was great variation in each Space Marine Legion's order of battle and size. However, in the most generalised sense, a Space Marine Legion was a force comprised of approximately 11 or more smaller sub-units known as "chapters", each subsequently further divided into a deep hierarchy of smaller sub-units led by officers whose rank terminology often differed from Legion to Legion.

The order of battle presented here should be considered generic and to be superseded by the more specific structure and rank terminology of a given Legion, if such information is available within current Imperial records.

• Legion Command: Primarch or Legion Master (if the Legion's primarch had not been rediscovered)
  • Praetorate or Ancients of the Legion (Senior Staff Officer Cadre)
    • Consular Representatives [Senior representatives of the Armourium, Astropathic Chamber, Navigators-Plenipotentiary, Librarus (if present in Legion), Apothecarion, Masters of the Fleet, Castrum of Ordnance, Castellans of Domain, et al]
    • Vexillarius (Legion Standard Bearers, Subalterns and Equerries)
    • Honour Guard (Praetorian Bodyguard Formations for Primarch -- number and structure varied by Legion)
    • Legion Assets:
      • Planetary Domains
      • Capital Class Warships
      • Secondary Escort Squadrons
      • Legion Armourium
      • Legion Apothecarion
      • Legion Librarus (if present in Legion)
      • Auxiliary Forces (Non-Space Marine, usually Imperial Army)
      • Legion Support Corps (Victuallers, Commissary, Legion Serfs, Indentures, Servitors, etc.)
• Chapter I (Chapters were alternatively designated as Great Companies, Harrows, Millennials, etc.)
  • Originally each Chapter was composed of roughly 1,000 line Astartes, but as the Legions grew, this number began to vary substantially by Legion, and also through the vicissitudes of war and the availability of replacement recruits
• Chapter II
• Chapter III
• Chapter IV
  • Battalion I (Battalions were alternatively designated as Cohorts, Regiments, Battle Groups, etc.)
    • Battalion Command (Example): Lieutenant Commander (alternatively designated as Commander, First Captain, Shadow Captain, Marshal, Legate, etc.)
      • Battalion Consuls (Senior Specialists and Advisors)
        • Battalion Vexillarius (Standard Bearers, Subalterns and Equerries)
        • Battalion Command Bodyguard
        • Battalion Assets:
          • Strike Cruisers
          • Navigators Ordinary
          • Drop Pods and Rams
          • Light Gunship Squadrons
          • Super-heavy Detachments
          • Skimmer Strike Detachments
          • Support Artillery Detachments
          • Techmarine Covenants
          • Apothecarion Sections
          • Dreadnought Talons
          • Reconnaissance Sections
        • Company I (Companies were alternatively designated as Maniples, Bands, Brotherhoods, etc.)
          • Nominally Battalions numbered five companies, each of a hundred Legionaries -- Company I was composed of Veterans and other elite units, II, III and IV were line companies and the V Company was comprised entirely of specialist troops such as dedicated Assault, Outrider or Destroyer units. However, in practice many larger Legions regularly exceeded this number of companies, maintaining battalions with seven or ten companies each folded under a particular command, while individual companies also varied in strength
        • Company II
        • Company III
        • Company IV
        • Company V
          • Company Command (Example): Company Captain (alternatively Centurion, Prime, Wolf Lord, Blooded, etc.)
            • Company Standard Bearer
            • Company Command Bodyguard Squad
            • Company Assets:
              • Heavy Support Squads (5-10 Space Marine Legionaries)
              • Assigned Veteran or Specialist Squads (Various)
              • Gunships
              • Rhino Armoured Transports
              • Tank Detachments
              • Support Weapons Batteries
              • Dreadnoughts
              • Techmarines
              • Apothecaries
            • 1st Lieutenant
              • Lieutenants were the most junior officers of the Legion. They also differed in designations such as Dominar, Decurion, Pack Leader or Chieftain, and in some Legions the numerical positioning of the officer within the Company indicated seniority or ceremonial role and had further titles in rank
              • Legion Tactical Squad (10-20 Space Marine Legionaries)
              • Legion Tactical Squad (10-20 Space Marine Legionaries)
              • Support Squad (5-10 Space Marine Legionaries)
            • 2nd Lieutenant
              • Legion Tactical Squad
              • Legion Tactical Squad
              • Legion Tactical Support Squad
            • 3rd Lieutenant
              • Tactical Squad
              • Tactical Squad
              • Legion Tactical Support Squad
        • Company VI
        • Company VII (etc.)
  • Battalion II
• Chapter V
• Chapter VI
• Chapter VII
• Chapter VIII
  • Chapter Command (Example): Lord Commander (Alternatively Chapter Master, Khan, Warsmith, Magister, etc.)
    • Chapter Consuls (Senior Specialists and Advisors to the Lord Commander)
      • Chapter Vexillarius (Chapter Standard Bearers, Subalterns and Equerries)
      • Chapter Command Bodyguard
      • Chapter Assets:
        • Chapter Flagship Battle Barge/Capital Ship
        • Planetary Assault Craft and Drop Ships
        • Escort Squadrons
        • Gunship Squadrons
        • Chapter Armourium
        • Legion Armoured Divisions
      • Battalion I
      • Battalion II
        • Nominally each battalion was composed of five hundred line Legionaries each, as well as various specialists and support staff
• Chapter IX
• Chapter X
• Chapter XI (etc.)

Original Legion Names

The Legiones Astartes were for a very long time after their initial creation under the direct command of the Emperor and originally all Space Marine recruits were drawn from Terra itself rather than the later Legion homeworlds of the primarchs.

The Terran Space Marines would always remember these early times before their primarchs were re-discovered and the Legions initially had overwhelmingly Terran cultural traditions and origins. Later, as the primarchs were re-discovered, the new recruits would have very strong loyalties towards them, and some of the primarchs would re-name their Legions to accord with their own personalities and cultural sensibilities.

The Emperor saw no problems with this development; He believed the loyalty of the primarchs to Him was unshakable. This reasoning would be proven to be sadly mistaken; for all their seeming physical and mental perfection they were still Human beings and prone to all the sins of Humanity, including greed, anger and the lust for power, recognition and advancement -- all emotions that left them susceptible to the temptations offered by the Ruinous Powers of Chaos.

The first primarch to be found was Horus Lupercal, rediscovered on the Mining World of Cthonia in 801.M31. He was always the Emperor's favourite, and he and his XVI^th Legion, the "Luna Wolves", were granted the honour of being renamed the "Sons of Horus" following Horus' elevation to the rank of Warmaster, and his survival despite the wound that had nearly killed him on the Nurglish plague moon of Davin.

The I^st Legion was given the name "Dark Angels" by Lion El'Jonson, and the XIV^th Legion, the Dusk Raiders, had their moniker changed to the Death Guard by Mortarion.

While its original name is unknown, the great honorific "Emperor's Children" was awarded by the Emperor to the III^rd Legion only after a speech made by their recently-rediscovered primarch Fulgrim so impressed the Emperor that He granted that coveted moniker to Fulgrim's Legion, as well as the sole right to wear the Palatine Aquila upon their chest plates of their power armour.

The V^th Legion was originally called the "Star Hunters" before being reunited with their primarch Jaghatai Khan, who renamed them the "White Scars".

The IX^th Legion was known as the "Revenant Legion" early in the Great Crusade. This was because of its penchant for taking recruits who were suffering from genetic and environmental diseases and remaking them as healthy Astartes and because its Astartes often took on the identities of senior officers who were slain in battle, using their mutated Omophagea implant to ingest their flesh and gain their memories and skills. To outsiders, it seemed that many of the Astartes of the Revenant Legion kept returning from certain death. When the Primarch Sanguinius was reunited with his Legion, he renamed them the Blood Angels, determined to remake them in his more noble image.

The XII^th Legion was originally known as the "War Hounds" by the Emperor before the primarch Angron renamed them the "World Eaters".

The XVII^th Legion, the Imperial Heralds, were renamed the Word Bearers after they were reunited with their highly religious Primarch Lorgar, who tragically intended to bring word of the Emperor's divinity to every world that his Legion brought into Imperial Compliance.

The XX^th Legion was originally kept a secret from even the other primarchs and its existence was only rumoured as that of the "Ghost Legion". Later, after the Legion began to operate more openly, if still covertly, some time in either the solar decade immediately preceding the commencement of the Farinatus Extermination or as appearing as an unexpected reinforcing power during the darkest days of the Third Rangdan Xenocides, it was renamed as the "Alpha Legion".

Initial Heresy Deployments

Loyalist Legions

Even as acts of wanton brutality and mindless treachery, the opening stages of Horus Lupercal's rebellion against the Emperor during the Isstvan III Atrocity and the Drop Site Massacre of Isstvan V were fastidiously planned. The Warmaster's initial goal was to cripple those Loyalist Space Marine Legions which could not be turned against the Imperium, and leave the way clear for his rapid drive on Terra and victory.

The cruel genius of the Warmaster's plans was how he isolated so many of the major threats before the civil war had even truly begun. Ferrus Manus, renowned as one of the greatest battlefield commanders in the Imperium, was baited into a brutal, one-sided fight. Roboute Guilliman, with all the might of his vast Ultramarines Legion, was kept isolated from the main Imperial effort and the Wolf King Leman Russ was manipulated by Horus into spending much of his Legion's might breaking the Thousand Sons on Prospero.

Yet Space Marine Legions were vast and often spread widely throughout the galaxy at the time of the Great Crusade. It is impossible to account for the entirety of their strength in this period, but Imperial scholars of the 41st Millennium do have a decent idea of where they mostly were at the time of the Drop Site Massacre in ca. 566.006.M31.

• Dark Angels - Even before he made his first treacherous move, Horus knew Lion El'Jonson would have no part of his schemes. Rather than face the Dark Angels from the onset, he simply used his position as Warmaster to order the I^st Legion far from Terra and far from the Isstvan System. In a stroke, one of his main foes was removed from the board. Once they learned of the Isstvan III Atrocity, the Dark Angels spent much of the Horus Heresy attempting to battle their way through back to Terra and vengeance.

• White Scars - Deployed to Chondax to cleanse it of an Ork infestation, the White Scars found themselves battling against an unexpected and mysterious foe. This was later revealed to be elements of the Alpha Legion, acting under orders from the Warmaster. The Jaghatai Khan's response was to break free of their blockade during the Chondax Campaign, and race for Terra -- where they would ultimately fight as an integral part of the defence of the Imperial Palace.

• Space Wolves - Sent to bring Magnus the Red to justice for his wanton disregard of the Edicts of Nikaea with his psychic penetration of the wards placed upon the Imperial Palace through the use of forbidden sorcery, Leman Russ and his Space Wolves were manipulated by the Warmaster. Instead of bringing Magnus back to Terra to face justice as the Emperor had intended, Russ unleashed the fury of his Censure Host and devastated the Thousand Sons' homeworld during the campaign remembered as the Burning of Prospero. Magnus escaped with the aid of the Chaos God Tzeentch, effectively driven into the Warmaster's treacherous designs despite his determination to warn the Emperor of Horus' treachery. Upon learning of Horus' betrayal at Isstvan III, Russ and his gene-sons swore oaths to hunt down the Traitor Warmaster and all his allies.

• Imperial Fists - When the Emperor withdrew to Terra to accomplish his great work of creating the Imperial Webway Project, he took Rogal Dorn and the Imperial Fists with Him. As the Warmaster fomented his schemes, Rogal Dorn and his Legion fortified Terra and transformed the Imperial Palace into an impregnable stronghold. When word reached Terra of the treachery on Isstvan III, Dorn organised the reprisal mission -- sending the mighty Imperial Fists Retribution Fleet to join his brothers. The fleet would never arrive at its intended destination, instead emerging from the Warp through the machinations of the Ruinous Powers in the Phall System...and into the jaws of an Iron Warriors ambush of epic proportions. Even so, Dorn and his Imperial Fists would form the lynchpin of the Imperial defence in the approaching Solar War over control of the Sol System.

• Blood Angels - As the Horus Heresy began in the Isstvan System, the IX^th Legion were already in a terrible strategic position. Horus had ordered the Blood Angels and their primarch Sanguinius to Signus Prime, where they faced the Daemonic horrors of the Warp in the terrible Signus Campaign. This was a calculated move on the part of Horus, who sought to remove one of the mightiest of the Emperor's gene-sons and perhaps his greatest rival from any ability to interfere with his plans -- or even better, turn Sanguinius to the side of Chaos. The battle on Signus Prime between Sanguinius and the Khornate Bloodthirster Ka'Bandha left scars on the psyche of the Legion and its primarch that would haunt them forever more. Battered and bloodied, the Blood Angels learned of Horus' rebellion during the campaign and set off on the long road to Terra, which would take them nearly seven standard years to reach as a result of the Traitors' conjuring of the Ruinstorm.

• Iron Hands - Driven to insensate rage by Horus' treachery and personally aggrieved that his beloved brother Fulgrim of the Emperor's Children had turned against him and the Emperor, Ferrus Manus led the X^th Legion to Isstvan V, committing many thousands of his Legion, including his elite Veteran companies. The Iron Hands were a respected and formidable Legion, but Horus manipulated their expected obsessive drive for vengeance -- and so they charged headlong into the Traitors' trap. Ferrus Manus died at Fulgrim's hands during the Drop Site Massacre and his Legion was broken. The remnant scattered, rallying in disparate groups and launching a campaign of vengeance that would last the remainder of the civil war.

• Ultramarines - The most numerous of the Space Marine Legions by the dawn of the 31st Millennium, the Ultramarines posed a terrible threat to Traitor schemes. To neutralise them, Horus turned to Lorgar and his Word Bearers and the pretence of a rapprochement for a former feud between Lorgar and Roboute Guilliman over the humiliation the Word Bearers had suffered at the world of Khur four solar decades before. On the planet of Calth in the Realm of Ultramar, the two Legions came together, but the veneer of friendship was shattered as the Word Bearers perpatrated a massacre upon the Ultramarines and the people of Calth. The system was devastated and its star killed, in an act of terrible ritual significance -- the catalyst for the emergence of a galaxy-wide Warp storm that prevented effective astrotelepathic communication and Warp travel for the Loyalists. Cut off from Terra by this "Ruinstorm", Guilliman and his gene-sons rallied, rebuilt and fought to secure the Five Hundred Worlds of Ultramar from the continued assault of the Word Bearers and World Eaters.

• Salamanders - Readily joining the Imperial reprisal fleet sent to Isstvan V on the orders of Rogal Dorn, the Salamanders were part of the first Loyalist wave into the drop site. The result was the disaster of the Drop Site Massacre, the Legion's backbone broken and its primarch, Vulkan appeared slain by a tactical nuclear strike unleashed by the Traitors. Blooded and beaten, the Salamanders were not quite out of the fight. Surviving elements would regroup and battle on, often alongside other survivors of the Isstvan V massacre. As for Vulkan, he later became the key to the Imperial defences upon Terra due to his immortal nature as a Perpetual, first revealed at Isstvan V.

• Raven Guard - The third of the Loyalist "Shattered Legions" crushed in the Drop Site Massacre, the Raven Guard were haunted by their failure. Among the smallest of the Legions from the start, they were nonetheless well-suited to fighting in unorthodox ways -- and they put these skills to good use terrorising the Traitors at every turn. As his Legion fought a brutal guerilla war against the Warmaster's forces, Corvus Corax sought a way to rapidly replace his Legion's tragic losses...a quest that would ultimately lead to further disaster through the machinations of the Alpha Legion.

Traitor Legions

At the onset of the Horus Heresy, the Traitor Legions found themselves in an advantageous position: three Loyalist Legions had been broken at the Drop Site Massacre on Isstvan V, and most of the others were out of position due to the Warmaster's treacherous pre-war scheming.

The Traitors ended the Drop Site Massacre in a position of great strength. The Loyalists were fragmented -- and in some cases decimated -- and the galaxy was apparently ripe for the taking.

• Emperor's Children - Flushed with victory on Isstvan V and jubilant at the personal triumph of Fulgrim over Ferrus Manus, the Emperor's Children were ready for the long road to Terra. While there would be no shortage of battles along the way, the main detour for portions of the III^rd Legion was into the Eye of Terror in search of the supposed Aeldari weapon known as the Angel Exterminatus, where Fulgrim ascended to Daemonhood with a little (unwilling) help from his brother Perturabo. Flooded with Daemonic power, Fulgrim and his increasingly corrupted warriors joined the Siege of Terra at Horus' bidding, though tales of their savage, sensation-seeking raids upon the other settlements of the Throneworld would last for standard millennia afterwards.

• Iron Warriors - Participating in the second wave of the Drop Site Massacre with their customary brutal efficiency, the Iron Warriors were destined to go on to fight in some of the best-known battles of the Horus Heresy, such as the Battle of Phall and the Battle of Tallarn. Ultimately, the Iron Warriors destiny lay on Terra. Perturabo served as the strategic lynchpin to the Warmaster's grand designs to penetrate the Imperial Palace during the Siege of Terra, but he was never happy about it.

• Night Lords - Another participant in the second wave on Isstvan V, the Night Lords set out to wreak havoc across the Imperium, before joining the bulk of Horus' forces for the assault on the Sol System. Along the way, they would become entangled with the Dark Angels in the Thramas Crusade, and for a time Konrad Curze even found himself captured by the I^st Legion and imprisoned aboard its flagship, the Invincible Reason.

• World Eaters - Having purged their ranks of the Loyalists on Isstvan III and drenched themselves in the blood of their foes at the Drop Site Massacre, the World Eaters revelled in the glorious slaughter the Horus Heresy offered. From Isstvan V, they passed straight to Ultramar, where Angron was raised to Daemonhood through the aid of Lorgar during the slaughter inflicted on his hated homeworld of Nuceria. Ultimately, their destiny, or so they claimed, was to lead the assault on the Imperial Palace during the Siege of Terra, where their Daemon Primarch confronted Sanguinius, the Winged Angel of Baal.

• Death Guard - The Death Guard were among the first four Traitor Legions, and cleansed their ranks of Loyalists on Isstvan III. However, there was a fly in their ointment. Their own Captain Nathaniel Garro escaped this purge and managed to warn the oblivious Imperium of the Warmaster's treachery. Because of this, Horus had to change his original plan of striking at Terra immediately, turning instead to the trap laid for the Loyalist Legions at the Drop Site Massacre on Isstvan V. The Death Guard advanced on the long road to Terra via a deeply traumatic detour in the Warp, emerging in the Sol System at the time of the Siege of Terra in 014.M31 forever changed, having become the Plague Marine champions of Nurgle.

• Thousand Sons - Following the crushing outcome of the Council of Nikaea at which their pro-psyker stance was rejected by the Emperor and they were ordered to end their exploration of sorcery, the Thousand Sons withdrew to their homeworld of Prospero. There they languished, playing no further part in the last days of the Great Crusade, nor the burgeoning rebellion, until Magnus the Red learned of Horus' treacherous plans. Using the exact type of sorcery that had earned him the Emperor's approbrium, Magnus tried to warn the Master of Mankind, but instead caused calamity on Terra when he penetrated the psychic wards protecting the Imperial Palace, inadvertently unleashing the War Within the Webway. The outcome was perhaps inevitable -- the Space Wolves led a Censure Host that shattered Prospero and the Thousand Sons, with the survivors fleeing into the Warp through the aid of the Chaos God Tzeentch and ultimately the warm embrace of the Warmaster. For Magnus and his gene-sons, a bitter revenge for all they had suffered awaited.

• Sons of Horus - As the Warmaster Horus Lupercal's own Legion, the Sons of Horus had the most to do in the wake of the great victory the Traitors had earned at the Drop Site Massacre on Isstvan V. Firstly, theirs was the duty and honour to orchestrate the push towards Terra -- but many challenges faced them. Elements of the XVI^th Legion devoted themselves to hunting down the remnants of the three Shattered Legions, while others crushed bastions of Imperial resistance. Behind all these actions was Horus' quest for more power with which to best his father -- taking him to the Knight World of Molech, where he would receive the blessing of all four Dark Gods. Ultimately, though, the Sons of Horus fought battle after brutal battle as they carved their bloody path towards Terra, and the final confrontation with the Emperor of Mankind.

• Word Bearers - The Word Bearers were involved in Horus' betrayal from the onset -- indeed, it's reasonable to say that the Horus Heresy originated within the XVII^th Legion some forty standard years before the Isstvan III Atrocity. They were instrumental in many of the opening gambits of the civil war, especially the Drop Site Massacre and the equally infamous Betrayal at Calth where they were responsible for using that great blood-letting as a sacrifice to unleash the galaxy-wide "Ruinstorm". The Word Bearers ultimately joined the march on Terra, during which their primarch Lorgar Aurelian played an instrumental role in corralling the Daemon Primarchs...though he would not always retain Horus' favour himself, believing himself to be the true champion of the Ruinous Powers.

• Alpha Legion - Always the most mysterious of the Space Marine Legions, the Alpha Legion were almost entirely inscrutable, and questions persist even into the 41st Millennium as to their true purpose and allegiance. Ultimately however, their actions speak for themselves: they joined the slaughter of the Loyalist Legions at the Drop Site Massacre. They went on to fulfil other roles too, sowing dissent and confusion on an almost galactic scale and plaguing the White Scars during the Chondax Campaign. One of their main duties was to penetrate the defences of the Sol System ahead of the main Traitor advance during the Solar War -- an act that would bring them into direct conflict with the Imperial Fists and face-to-face with Rogal Dorn at the Battle of Pluto in 010.M31.

Primarchs and Astartes Legions

Legion Number	Legion Colours	Legion Primarch	Legion Name (Original Name)	Legion Homeworld	Legion Allegiance	Primarch Current Status
I		Lion El'Jonson	Dark Angels (The First)	Caliban	Loyalist	Missing; body resided in stasis aboard The Rock, the Dark Angels' fortress-monastery, unbeknownst to the majority of his gene-sons until the Era Indomitus, when he re-awakened, much aged, with the ability to travel at will across the galaxy through the Warp.
II	Unknown
III		Fulgrim	Emperor's Children	Chemos	Traitor	Body formerly possessed by a Greater Daemon of Slaanesh once contained within the Blade of the Laer Fulgrim found on the world of Laeran. Fulgrim achieved apotheosis during the Horus Heresy and was transformed by the will of his patron deity into a Daemon Prince of Slaanesh.
IV		Perturabo	Iron Warriors	Olympia	Traitor	Perturabo achieved apotheosis and was transformed by the will of the Dark Gods into a Daemon Prince of Chaos Undivided.
V		Jaghatai Khan	White Scars (Star Hunters)	Chogoris	Loyalist	Disappeared into the Webway in pursuit of Dark Eldar raiders.
VI		Leman Russ	Space Wolves	Fenris	Loyalist	Disappeared into the Eye of Terror.
VII		Rogal Dorn	Imperial Fists	Terra / Inwit (Originally)	Loyalist	Believed slain during the 1st Black Crusade; skeletal remains preserved aboard the Phalanx in different chapels.
VIII		Konrad Curze	Night Lords	Nostramo	Traitor	Also known as the Night Haunter. Assassinated by Callidus Assassin M'Shen on Tsagualsa.
IX		Sanguinius	Blood Angels (Revenant Legion}	Baal	Loyalist	Dead; slain by Horus aboard his Battle Barge the Vengeful Spirit at the climax of the Battle of Terra. His death imprinted a psychic scar in the Blood Angels Legion's genetic memory, which is thought to be the cause of visions and afflictions like the Black Rage in carriers of their gene-seed.
X		Ferrus Manus	Iron Hands (Storm Walkers)	Medusa	Loyalist	Dead, beheaded by Fulgrim during the Drop Site Massacre on Istvaan V.
XI	Unknown
XII		Angron	World Eaters (War Hounds)	Terra / Nuceria (Angron's homeworld) / Bodt (Legion training world)	Traitor	Angron achieved apotheosis and was transformed into a Daemon Prince of Khorne by the will of the Blood God; he was recently banished back to the Warp during the First War for Armageddon.
XIII		Roboute Guilliman	Ultramarines (War-Born)	Macragge	Loyalist	Mortally wounded by Fulgrim at the Battle of Thessala in 121.M31; body kept in stasis in the Temple of Correction on the world of Macragge until 999.M41 when he was resurrected by Belisarius Cawl and the power of Ynnead to lead the Imperium once more against the Archenemy.
XIV		Mortarion	Death Guard (Dusk Raiders)	Barbarus	Traitor	Mortarion achieved apotheosis and was transformed into a Daemon Prince of Nurgle.
XV		Magnus the Red	Thousand Sons	Prospero	Traitor	Magnus the Red achieved apotheosis and was transformed into a Daemon Prince of Tzeentch.
XVI		Horus	Sons of Horus (Luna Wolves)	Cthonia	Traitor	Dead; utterly destroyed, mind, body and soul, by the Emperor of Mankind at the climax of the Battle of Terra.
XVII		Lorgar	Word Bearers (Imperial Heralds)	Colchis	Traitor	Lorgar achieved apotheosis and was transformed into a Daemon Prince of Chaos Undivided by the will of the Dark Gods; currently resides in "contemplation" upon the Word Bearers' Daemon World of Sicarus in self-imposed isolation, meditating within the Temple Inficioto as he seeks enlightenment and communion with the Ruinous Powers.
XVIII		Vulkan	Salamanders (Dragon Warriors)	Nocturne	Loyalist	Disappeared, location currently unknown.
XIX		Corvus Corax	Raven Guard	Deliverance	Loyalist	Disappeared, last seen heading for the Eye of Terror, known to have hunted Lorgar in the Warp for standard millennia, slowly mutated into a raven-like monstrosity by constant exposure to Chaos energies.
XX		Alpharius, Omegon (twins)	Alpha Legion	Unknown	Traitor (Possibly Loyalist)	One of the twins might be dead, slain by Roboute Guilliman after the Horus Heresy. Both twins sided with Horus and were declared Traitor by the Imperium; however they considered themselves to be opposed to Chaos and their actions may be one more subterfuge amongst so many.

See Also

• Blackshield
• Centurion (Space Marine Rank)
• Champion Consul
• Consul
• Consul Opsequiari
• Legion Delegatus
• Legion Esoterist
• Legion Forge Lord
• Herald
• Inductii
• Legion Mortifactor
• Legion Overseer
• Legion Pathfinder
• Legion Consul Praevian
• Librarian Consul
• Master of Signal
• Moritat
• Praetor (Space Marine)
• Primus Medicae
• Primus Nullificator
• Siege Breaker
• Vigilator (Space Marine)
• Warmonger

Sources

• Codex: Black Templars (4th Edition) pg. 20
• Codex: Blood Angels (5th Edition), pp. 6-8
• Codex: Blood Angels (7th Edition), pp. 6, 9-12, 34, 62, 175
• Codex: Dark Angels (4th Edition), pp. 6-12
• Codex: Dark Angels (6th Edition), pp. 6, 9-12, 14, 16, 18-19, 21
• Codex: Dark Angels (7th Edition), pp. 6, 8, 40, 43-44, 61, 66, 85, 109
• Codex: Space Marines (4th Edition), pp. 4-6
• Codex: Space Marines (5th Edition), pp. 6-9
• Codex: Space Marines (6th Edition), pp. 6-9
• Codex: Space Marines (7th Edition), pp. 7, 13, 68
• Codex: Space Wolves (2nd Edition), pp. 7-9
• Codex: Space Wolves (5th Edition), pp. 8-9
• Codex: Space Wolves (7th Edition), pp. 6-7, 9-11, 60
• Codex: Ultramarines (2nd Edition), pp. 6-9
• Realms of Chaos: Slaves to Darkness, pp. 240-244
• Age of Darkness Campaign: Siege of Cthonia (Supplement), pp. 30-32, 45-46, 48, 53, 60, 62, 65, 68-69, 71-72, 74, 79-80, 83, 88-90, 99-102, 108, 120-131, 146, 179, 224-234
• The Horus Heresy Book One: Betrayal (Forge World Series) by Alan Bligh, pp. 29-30, 79, 97, 109, 129, 189
• The Horus Heresy Book Two: Massacre (Forge World Series) by Alan Bligh, pp. 14-16, 18-19
• The Horus Heresy Book Five: Tempest (Forge World Series) by Alan Bligh, pg. 96
• The Horus Heresy Book Six: Retribution (Forge World Series) by Alan Bligh, pp. 21, 112, 115, 249 266
• The Horus Heresy Book Seven: Inferno (Forge World Series) by Alan Bligh, pp. 24, 32, 65, 84
• The Horus Heresy Book Eight: Malevolence (Forge World Series) by Neil Wylie and Anuj Malhotra, pp. 115-135, 137-157
• The Horus Heresy: Collected Visions (Background Book) by Alan Merrett, pp. 12-13, 16-21, 24, 27
• White Dwarf 98 (UK), "Chapter Approved: The Origin of Legiones Astartes" by Rick Priestly, pp. 12-17
• White Dwarf 129 (UK), "Space Marine Armor: Background," by Rick Priestley, pp. 13-29
• White Dwarf 166 (UK), "Space Marines: Codex Imperialis Extract - Legions of Adeptus Astartes," by Andy Chambers & Rick Priestley, pp. 8-19
• Horus Rising (Novel) by Dan Abnett
• Descent of Angels (Novel) by Michael Scanlon, pp. 235, 303
• The First Heretic (Novel) by Aaron Dembski-Bowden
• Deliverance Lost (Novel) by Gav Thorpe, pg. 14
• Age of Darkness (Anthology) edited by Christian Dunn, "Rules of Engagement" by Graham McNeill
• Know No Fear (Novel) by Dan Abnett
• Shadows of Treachery (Anthology) edited by Christian Dunn and Nick Kyme, "The Crimson Fist" by John French
• Angel Exterminatus (Novel) by Graham McNeill
• Vulkan Lives (Novel) (Digital Edition) by , pg. 119
• Soul Drinker (Novel) by Ben Counter
• The Bleeding Chalice (Novel) by Ben Counter
• Warriors of Ultramar (Novel) by Graham McNeill
• The Unremembered Empire (Novel) by Dan Abnett
• Scions of the Emperor (Anthology), "First Legion" by Chris Wraight
• Warhammer Community - How big is a Space Marine Legion?
• Warhammer Community - Traitor lore – How the trap was set
• Warhammer Community - Loyalist lore – Where were the Legiones Astartes as the Horus Heresy broke out?