The Adeptus Astartes – the Space Marines – is an ancient warrior brotherhood created by the Emperor more than ten thousand years ago to help him reclaim the galaxy for Man. In the 41^st Millennium they are humanity's champions in the unending struggle for survival. A space Marine is not born, he is made. Made in the image of the Emperor. To make a Marine you recruit at an early age the most dangerous killers humanity has to offer, transform them into superhuman giants, teach them nothing but killing, and instil in them an unflinching loyalty to the Golden Throne and a willingness to die in service of the God-Emperor. Then you encase him in a suit of armour without equal and equip him with the deadliest weapons the Machine God has to offer. The end result is aptly called the Angels of Death; they descend from the heavens to smite the foes of Man with divine wrath.

CHAPTER ORGANIZATION

The Chapter is the largest Marine organizational unit commonly used in M41. During the Great Crusade the Marine Legions would each be composed of many Chapters. A Chapter was the Legion's smallest unit capable of sustained independent operations. It is a popular misconception that Chapters number 1.000 Marines. It is true that newly formed Chapters are made up of a cadre of only 1.000 Marines, plus a command staff taken from their progenitor Chapter, but that is probably the only time a Chapter will number exactly a thousand. In reality the number of Marines available to a Chapter varies quite a bit, as battle deaths and recruitment causes troop numbers to fluctuate. Each Chapter of Astartes has per the Codex Astartes a nominal fighting strength of 1.000 Space Marines, but that is 1.000 battle-ready Space Marines. To be able to field such a force, even for an organization as lean as the Marines, you need 2-3 warriors per position. Then there is an increasingly large command and support staff, plus a number of semi-retired Marines filling semi-honorary position (though most could fight if need be).

Although no Chapter is anywhere near in size to the massive million-strong Legions of old, there are some fairly big Chapters out there. The Black Templars, for example, are known to field at least 5.000 Battle-Brothers at any one time, which could mean that there are as many as 15-20 thousand Black Templars out there, not counting command and support or retirees. The Space Wolves remains the only non-traitor legion not to have complied with the Adeptus Terra with regards to the dissolution of the Legions. They still retain their original thirteen Chapters (though the 13^th has been lost in the Eye of Terror for quite some time), although some Administratum scribes have deftly evaded the truth by labelling the Chapters 'Cohortes Maximus' (i.e. Great Companies). The Space Wolves M41 Chapters are not, however, at their maximum Great Crusade size. Instead they are comparable to other marine Chapters of the present day and age. The Ultramarines are Codex-bound, but control a number of 'vassal' Chapters in and around the 'Kingdoms of Ultramar', thus easily outnumbering all other Chapters in terms of fighting men. Losses against Hive Fleet Behemoth and Hive Fleet Kraken have been considerable, with several vassal Chapters having been completely destroyed and others reduced to just a small cadre.

The Squad is the basic Marine tactical unit. It comprises 10 Battle-Brothers, one of which is a Sergeant. The Sergeant is invariably a battle-hardened marine that has displayed both leadership skill and unusual initiative. The rest of the squad's members are ranked according to seniority, although some awards, commendations and/or disciplinary black marks can cause changes in effective seniority. Regardless of battle deaths or incapacitations there will always be someone in command of the squad. Squad members are typically armed with bolters, except for two heavy weapons (frequently a heavy bolter and a missile launcher) and possibly up to two specialist weapons (such as a flamer or melta gun). Squads are very flexible can be broken down into smaller units, typically two five-man Battle-Squads led by either the Sergeant or a Veteran Brother (some Chapters name this marine Corporal, others have a second junior Sergeant per squad; both are fairly rare). One Battle-Squad might be assigned the heavy weapons while the other one takes the assault weapons; or each could have one heavy weapon assigned. Or one or both Battle-Squads can be split into two-Marine fire-teams as the situation warrants. Options are nearly endless; squads can quickly be made to match any situation.

Ten squads make a Company, led by a Captain. Some Chapters also have a separate position for a company Lieutenant. Those Chapters that do not have lieutenants lists the senior squad Sergeant as the company second-in-command. Companies are sometimes split into two 50-Marine Battle-Companies, led by the Captain and Lieutenant/Veteran Sergeant respectively. Companies can be further subdivided into any combination of squads as warranted by the battlefield situation. The Company (or Battle-Company) is the smallest tactical unit that is commonly deployed in an independent role; one Marine Company and supporting assets are considered sufficient to deal with most targets. This Marine Company Strike Force can easily be fitted into a single Strike Cruiser (most crusier models allow for even bigger forces, usually a maximum of 2-3 Companies worth of troops).

The number of companies to a Chapter will vary; but the basic 1.000 Marine line-up calls for ten companies, one of which is the Veteran/Terminator Assault Company and another which will be a Training/Scout Company. The remaining companies are Tactical Companies, although some Chapters operate with specialized companies – Jump Assault, Heavy/Devastator, Mobile Response, Urban Infiltrators, etc. These are roles that a normal Tactical Battle-Brother can fill, but within the ranks of the specialist companies each Marines focuses on that role to the exclusion of anything but basic Marine skills. Some Chapters wholeheartedly approve of such specialization as a means of pursuing perfection, while other Chapters frown upon it, claiming instead that each Marine should always be ready to face any challenge. Most Chapters are somewhere in between, maintaining just a few specialist companies and/or rotating Marines on a regular basis to avoid calcification within one narrow role. A Chapter is commanded by a Chapter Master. The Master is attended by a senior Commander (sometimes called a Praetor) who is the Chapter's second-in-command. Some Chapters lack a specific position for the Praetor and instead has the senior company Captain hold the honour.

It is very rare for an entire Chapter's battle-ready forces to be deployed at any one time. Instead a Chapter can be divided into two Cohorts, commanded by the Chapter Master and Praetor respectively (one would normally be in the field while the other remains at base and attends to other duties, including permanent garrisons and patrols). For larger Chapters the Cohort formation can become permanent and there may be multiple Cohorts (usually of 5 companies each), each led by a Commander (one of which may also be the Praetor, unless that is a separate position). Some large Chapters, such as the Crimson Dawn Chapter, also maintain a position of Lieutenant-Commander for the Cohort second-in-command. A Space Marine Battle Barge can accommodate one five-company Cohort, support elements, and logistics train (it would e very rare, however, for a Barge to operate alone, without the benefit of support vessels).

All Chapters also have several supporting branches; the Librarium provides both astropaths and battlefield psykers, while Mechanicus-trained Tech-Marines take care of advanced maintenance rites (line personnel are expected to do undertake ordinary maintenance rites of personal and unit gear). Chaplains are tasked with caring for the spiritual well-being of the Battle-Brothers, while Marine Apothecaries are highly skilled in both first aid and advanced medical procedures. Lastly are the Battle-Brothers that are not assigned to any ready-unit, for whatever reason – they could be recuperating, receiving specialist training, be assigned as starship crew, or be semi-retired.

Most Chapters will also have extensive (non-Marine) non-combatant support staffs, offering additional logistical support. After all, someone must take care of the mundane affairs of a Chapters, be if distribution of supplies, refuelling drop-ships, acting as medical orderlies, preparing and serving meals, and so on. Some Chapters rely on serfs, others heavily on servitors, while a few even have free-men retainers who are paid for their services.

A Chapter's non-personnel assets also vary considerably. A new Chapter will be given a homeworld and recruitment rights there, as well as support staff, vehicles and a small fleet of ships, but after that they are expected to fund and fend for themselves. Old and successful Chapters can amass huge fiefs and the resources that go along with them (though they must be wary of gaining too much power, lest the Adeptus Terra become concerned.