A Company is one of the standard organisational units within a Space Marine Chapter, normally comprised of 100 Astartes led by an officer with the rank of Captain. It is the largest of such formations within a Chapter, and a single Company of Astartes is a force to be reckoned with on the battlefield, fully apt to engage and destroy the enemies of Mankind without any external support.
The Space Marine Legions (also known as the Legiones Astartes) were the original unit formations of the Space Marines created during the First Founding by the Emperor of Mankind on Terra in the late 30th Millennium. A Space Marine Legion was a frontline force of shock-infantry comprising tens of thousands of 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 at the end of the Horus Heresy, could number anywhere from 10,000 to more than 250,000 Space Marines. The 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 Primarch and his officers.
Much of the discipline and organisation of the early Astartes Legions owed greatly to the ancient and proven Terran patterns of strategy, hierarchy and functions as laid down in the revered texts of the Principia Belicosa of Roma and Krom's 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 Legionaries themselves. At the outset of the Great Crusade, circa 798.M30, many of these early Legions were organised along the so-called "Terran Pattern" of organisation as formulated by the Imperial Officio Militaris.
By the time of the outbreak of inter-Legionary hostilities during the Istvaan III Atrocity, 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 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, 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 rather than the desires of the Imperium's central administrators for a common 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).
The heart of most Space Marine Legions was the company, which served as the Legion's principal military division. Made up of a grouping of squads under the leadership of an officer with the rank of Captain, the company was the base currency of campaigns and battles. Within some Legions, such as the Sons of Horus, there was no fixed strength for a company. While other Legions codified and enforced strict limits on the size of similar formations, this was not the case amongst the Sons of Horus, which had begun in more regimented form, but had become increasingly ad hoc in structure and disposition over time. Company strengths as small as 36 and as large as 972 Astartes were recorded by datafactors during the XVI Legion's action against the Dasim Patrimony, for example. The configuration of squad types within a company varied as widely as its strength. Some were comprised almost exclusively of Tactical Squads with a few Support Squads. Others were an eclectic mix based on the varied requirements of different campaigns and the will of their Primarch Horus.
In other Space Marine Legions a company would form part of further layers of hierarchical military organisation, variously referred to as battalions, cohorts, chapters, regiments or by any number of other titles. Horus seems to have preferred to avoid this extra layer of fixed organisation, which eroded over time in the XVI Legion and was largely academic by the time of their transition to become the Sons of Horus. Instead of a formal structure, Horus would group companies and individual units together as required for the execution of a particular campaign. The commander of such a formation would usually be a senior Captain. If the formation was especially large, then other Captains would take on the role of lieutenants to the overall force commander until the completion of the campaign. These formations rarely had formal titles, but the Sons of Horus commonly referred to formations intended to prosecute a rapid assault as "Speartips." In eschewing formality and fixed structure above the basic level of the company, Horus demonstrated his pragmatism and his preference for waging war with careful precision. Within the Luna Wolves and the Sons of Horus, squads also commonly had their own honorific or epithetic titles rather than simple numerations: the Illuminators Prime, Death Makers, Jerrok's Reavers, the First Sons, and similar appelations, while some were named for the Sergeant or Chieftain that led them if their leader's own reputation was strong enough alone. Many of these titles betrayed the culture of Cthonian gang honours and the tradition of reputation and internecine warfare from which they had sprung. This culture had grown steadily stronger over the years within the rank and file of the XVI Legion's intake of Neophytes.
In the wake of the calamity that was the Horus Heresy, the foundations of the present-day Imperium were laid down. The first High Lords of Terra established the structure by which the Adeptus Terra operated, and described the feudal responsibilities and duties of the Planetary Governors. One of the most important accomplishments was the reorganisation of the Imperium's military forces. This was undertaken almost single-handedly by the Primarch of the Ultramarines Legion, Roboute Guilliman, who with his characteristic speed and efficiency codified the structure of the Imperial Guard, the Imperial Navy, and the Space Marines. Of all of his works, the most influential is the Codex Astartes, the great prescriptive tome that lays down the basic organisational and tactical rules for a Space Marine Chapter. The Codex Astartes decreed that Space Marines would be created and trained over a controlled period of time.
The Chapters that rigidly follow the word of the Codex Astartes are sometimes referred to as Codex Chapters or Codex Astartes-compliant Chapters. These Space Marines adhere to the Codex as the model for their organisation, identification markings and tactical doctrine. Of all the Codex Chapters, the most famous is the Ultramarines, the Chapter of Roboute Guilliman himself. Most Chapters, however, do not adhere so rigidly to the Codex patterns laid down for organisation, tactical roles, or other processes. Many Chapters are organised largely according to the Codex, but are further shaped by their homeworld and the personality of their Primarch. The Blood Angels and Dark Angels are prime examples of these. A small number of Chapters are vastly different from the Codex, and owe little or nothing to its prescriptions at all. The most famous of these non-Codex Chapters are the Space Wolves, whose strong-willed Primarch Leman Russ moulded his Chapter very much in his own image, irrespective of other influences. The Adeptus Terra has never decreed it necessary to enforce the Codex absolutely. Indeed, it is doubtful whether it could if it so chose. Each standard Codex Astartes-compliant Space Marine Chapter is composed of 10 companies: The 1st Company, which includes the Veteran Space Marines of the Chapter, the 4 Battle Companies (2nd, 3rd, 4th, 5th) composed of already battle-hardened Astartes, 4 Reserve Companies (6th, 7th, 8th and 9th) grouping those Battle-Brothers who are still in some way learning to master all the tools of war, and the 10th Company containing all the Scout Marines who are still in the process of becoming full Astartes.
In theory, each of the ten companies is self-sufficient in terms of personnel and materiel, and able to operate on its own. When faced with a call to war most Chapter Masters tend to assign a single Battle Company to deal with the problem and supplement that company with smaller elements from the 1st Company, Reserve Companies and/or Scout Company, depending on the foe they are facing. This way of waging war has proven its worth in countless engagements since the end of the Horus Heresy and the Second Founding reforms instigated by Roboute Guilliman.
Each company has roughly 100 Space Marines plus support staff (except the Scout Company which has no pre-determined number of warriors or squads). Veteran Companies have 100 Veteran Astartes who can go to battle in either standard Power Armour or Terminator Armour. Thus, Veteran Companies can have up to 20 5-man Terminator Squads, 10 10-man Veteran Squads, or some combination of both. Battle Companies have 6 10-man Tactical Squads, 2 10-man Assault Squads, and 2 10-man Devastator Squads. Reserve Companies have 10 10-man squads, all of the same type. The first 2 Reserve Companies contain 10 10-man Tactical Squads. The third Reserve Company has 10 10-man Assault Squads. The fourth Reserve Company has 10 10-man Devastator Squads. Scout Companies have variable numbers of Scout Squads and squad sizes. Each company usually includes officers (Captains, Chaplains, Apothecaries, and standard bearers), as well as Dreadnoughts, Rhinos, Attack Bikes, Land Speeders, and Land Raiders. Other officers (Librarians, Techmarines, etc.) and vehicles (Predators, Whirlwinds, Vindicators, etc.) are held by the company command, which is not an independent fighting unit. When its members and vehicles fight, they do so alongside those of the company.
- Codex: Space Marines (6th Edition), pp. 24-25
- Codex: Space Marines (5th Edition)
- Codex: Space Marines (4th Edition)
- Imperial Armour - The Horus Heresy: Betrayal - Book One
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