Company (Space Marine) - Post-Heresy: 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, named the lord commander of the Imperium and the Imperial Regent in the wake of the Siege of Terra, who with his characteristic speed and efficiency codified the structure of the Astra Militarum, the Navis Imperialis, and the newborn Adeptus Astartes.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 relatively lengthy and controlled period of time, largely due to the fact that the easy corruption of so many Space Marines during the Heresy was believed to be the result of the accelerated means used to both create and train the Astartes of the late Great Crusade period.The Chapters that rigidly follow the word of the Codex Astartes are sometimes referred to as "Codex Chapters" or "Codex-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 the culture of 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-warrior Tactical Squads, 2 10-warrior Assault Squads, and 2 10-warrior Devastator Squads.Reserve Companies have ten 10-warrior squads, all of the same type. The first 2 Reserve Companies contain 10 10-warrior Tactical Squads. The third Reserve Company has 10 10-warrior Assault Squads. The fourth Reserve Company has 10 10-warrior Devastator Squads.Scout Companies have variable numbers of Scout Squads and squad sizes. Each company usually includes officers (captains, Chaplains, Apothecaries, and Ancients), as well as Dreadnoughts, Rhinos, Attack Bikes, Land Speeders, and Land Raiders.Other officers, such as 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.