Codex Astartes

"The Codex Astartes is a set of rules. They guide us. Shape us as Ultramarines. Teach us how to hold duty and honor sacred above all. But how we live with those rules is the true test of a Space Marine."
-Captain Titus, Ultramarines 2nd Company

The Codex Astartes is the collective name given to a series of tactical and organisational guides written by the Primarch Roboute Guilliman over the course of his life, compiled at the end of the Horus Heresy. The Codex's organizational mandates split the remaining Space Marine Legions into smaller chapters, for reasons discussed below. It also includes many tactical doctrines and stratagems for just about every situation, like the formidable STEEL REHN! Most loyalist Space Marine chapters follow the Codex Astartes to varying degrees, with Ultramarines and their successors seeing it as literal holy writ, while some chapters like the Black Templars and Space Wolves merely see it as a book of tactics to be referred to when necessary. Most chapters will fall somewhere between those two extremes, using the codex where necessary but making adaptations where necessary. Almost all chapters will make a few minor alterations at the very least, usually just superficial things accounting for the chapter's culture.

Chapters

Under the Codex Astartes, the Space Marine legions were to be split into groups of 1000 fighting men, called a Chapter. While many people assume this means a chapter is composed of 1000 men, this is a bit misleading, because that 1000 man number does not include a chapter's upper echelons, support structure, auxiliary units, dreadnought-interred veterans, the librarius, vehicle crews, honor guard, and specialists (tech marines, apothacaries, chaplains, etc). This means that a chapter will commonly have upwards of 1100 space marines while still being codex compliant, and many chapters will have large units of mortal retainers to serve as auxiliary forces, so it's not uncommon for a chapter to have tens of thousands of soldiers to call upon, though only a minority of them will actually be Adeptus Astartes. It's worthy of note that the Chapters was already a common sub-unit within some pre-Heresy legions like the Blood Angels, Dark Angels, Salamanders, Ultramarines, and Word Bearers. The 1st Company is composed of Veterans, and only marines who have served in the first company are allowed to wear terminator armor

The 2nd, 3rd, 4th, and 5th Companies are Battle Companies, composed of six Tactical Squads, two Devastator Squads, and two Assault Squads. They train together, and when a Space Marine Company deploys as a single unit, it will be one of these. The 6th, 7th, 8th, and 9th Companies are Reserve Companies, and are more specialized than the first five companies. The 6th and 7th Companies are composed entirely of Tactical Marines (who specialize in using bikes and Land Speeders, respectively), the 8th Company of Assault Marines, and the 9th Company entirely of Devastator Marines. The 10th Company is composed entirely of Scout Marines, who are eventually promoted to other companies after a certain number of years. It's worthy of note that the 10th company is typically the largest in the chapter, containing 100 neophytes in addition to veterans seconded to the company for training. Additionally, the 10th company's 100 man limit is often uncapped so as to keep the chapter's flow of new marines steady in times of great loss.

Roles Outside of the 1000 Man Limit

As mentioned above, the traditional "limit" of 10 companies of 10 squads of 10 soldiers each does not apply to a variety of positions in the Chapter, allowing a Chapter to have no theoretical maximum number of Space Marines, even before accounting for non-Astartes members, such as servitors or serfs. These positions include:

• Company Command Staff: Each company is allowed command staff which do not count against its limit or that of any other company.
  • Company Captain
  • Company Standard Bearer
  • Company Champion
  • Company Command Squad: A squad of up to 10 Marines, intended by the Codex as the Captain's bodyguards.
• Chapter Command Staff: Just like the Company Command Staff, the Chapter is allowed command staff which does not count against any company's limit.
  • Chapter Master
  • Chapter Standard Bearer
  • Chapter Champion
  • Honour Guard: Chapter-level equivalent to a Company Command Squad.
• Specialist Groups: There are four roles Marines can be assigned to which formally removes them from Company membership:
  • The Apothecarion: A chapter may have any number of apothecaries, although the Codex mandates at least 11 (1 per Company, plus the Chief Apothecary).
  • The Chaplaincy: A chapter may have any number of chaplains, although the Codex mandates at least 12 (1 per Company, plus the Reclusiarch and the Master of Sanctity).
  • The Armoury: A chapter may have any number of techmarines, who are not formally in any Company. Even more significantly, vehicle crew, including the driver/pilot and any gunners, count as members of the Armoury, not as members of a Company, which is why Dreadnoughts do not count against the 1000 member limit, as they are listed as permanently crewed vehicles in the Armoury (which might open a window to abuse it if a Chapter has sufficiently enough Dreadnought sarcophagi).
  • The Fleet: A chapter is allowed a fleet of as many ships as it can get together, and may assign Marines to these ships as permanent staff, in a similar fashion to the Armoury, although the Codex is significantly more flexible on Fleet staff (see Lord Admiral below; a chapter can be Codex compliant without any Marines in their Fleet at all).

What the Codex set out to Accomplish

The Codex Astartes was written with three main purposes in mind.

First, the Codex is a tactical and strategic guide. It contains tips and plans on how to handle nearly any battle situation imaginable, and then some. The Codex served with flying colors until the modern day of the setting, when its weaknesses began to show against certain unconventional enemies. Much like The Art of War or the FBI tactical guidebook, if you can get your hands on a copy you can anticipate the actions of those that use it, but countering it is really fucking hard because of just how comprehensive the Codex is. It doesn't just tell you "When your enemy is doing B, do C to counter it," it also says, "And when the enemy counters C with X and Y, use Z to shut down their counter." Sun Tzu's Art of War is still being taught millenia after its publication; now imagine that same spark of tactical genius manifesting inside the mind of a superhumanly intelligent demigod. The Codex isn't perfect - no tactical treatise is - but it's damn close.

Second, the Codex is an organizational guide. Guilliman was a flawed genius, an organizational savant literally unmatched in the galaxy, and more than a little OCD when it came to detail. Beyond simple mandates about the composition of the Chapters, the Codex contains information on the minutia of administration. Details on every subject from bolt shells to bread, water distribution to weapon production, organization of auxiliary forces, suggested countermeasures to viral outbreaks, training schedules, troop morale, ammunition production, distribution of that ammunition to terrestrial and naval combat units, how large reserves can be built up, how long those reserves will last when production stopped, ration distribution for militant and civilian populations, how those rations can be stored, food cycling to avoid waste, integration of chain of command with allied and auxiliary forces, integration of militia into formal military, suggested staging area locations relative to battle lines, suggested landing area locations relative to battle lines, prioritizing access to and from these areas, guides to avoiding massive compound sentences, fortification locations, demolition strategies for those fortifications in the event that they must be abandoned, and I could go on. It also has plenty to say on how to live your day to day life, with everything from codes of honor to follow, to how your boots should be laced. Seriously, the Codex can tell you how to spend every minute of your life from birth to death, and pretty much every part of it is either acceptable or outstanding, if admittedly inflexible.

Finally, and perhaps most importantly, the final version of the Codex is designed to keep the power of the Imperium decentralized. At the end of the Heresy, Guilliman wanted to ensure there wouldn't be any repeating performances of the strike that had gripped the galaxy. To this end, he set up the Council of Terra, split the Imperial Army in the the Imperial Navy and the Imperial Guard, and broke up the Legions, to keep one person from ever having the power to cause such massive chaos. Whether or not this was a good move is a subject of ongoing debate. Detractors would point out that the newly decentralized and feudal Imperium is nowhere near as capable of unified action as it was before the heresy, while its defenders would point out the examples of Huron Blackheart or The Mecharius Crusade as examples of too much centralized power devolving into a clusterfuck. One thing that is objectively better about the post-heresy Astartes is the shift in tactics leading to their more precise, focused battle plans. At some point people realize that you don't need a space marine to man a gun line or garrison a fort, and now the astartes are relegated to being an elite strike force rather than being mass infantry. During the Heresy days, you could loose a thousand astartes in a single battle and call it a victory, whereas in the modern day your average space marine battle will result in few marine casualties, if any. Part of this is simply a reaction to lessened resources, but on a fundamental level the modern surgical drop pod and deepstrike orriented marine armies take advantage of the astartes' strengths more than deploying them as mass infantry does. The modern marine armies are modular, precise, and efficient, qualities many of the original legions lacked. On top of that, when legion-sized deployments actually are necessary, they still happen, though the overpowering might of the legions would likely be more effective against certain unconventional foes like the Tyranids and the Necrons who are resistant to surgical strikes against their command structure.

Marine roles

Among the tenets of the Codex, Guilliman outlined the roles of various Marines to be used in Chapters. They include the following:

• Scout Squad: Scout Marines are Neophyte Space Marines who are charged with scouting terrain and enemy positions, in addition to demolitions and what we would today call special forces operations. A risky job, but this has the effect of ensuring that the more cautious ones survive while the reckless and foolish are weeded out.

• Devastator: Devastator Marines can be summed up in three words: Blow shit up. The purpose of the Devastator is to provide heavy weapons fire in battle, artillery strikes, and hunting tanks. Once a Scout earns his Black Carapace and Power Armor, he will be attached to a Devastator Squad, allowing him to gain battlefield experience by watching the conflict from afar, with the added perk of allowing a new marine to bond with his armor while learning its strengths by lugging heavy weapons around.

• Assault: Assault Marines are those who specialize in melee combat, using Chain and Power weapons alike to fuck up the enemies of the Imperium of Man. In addition, they also take to the field wearing jump packs which allows them to deepstrike onto the battlefield, move quickly from point to point, and even execute a jet-fueled charge of awesomeness into the enemy. This is the next stop in a new Marine's career when he graduates from the Devastator squads, helping to familiarize him with any weapons he hasn't used yet, and putting him through the crushing psychological stress of hand-to-hand combat under something resembling optimal conditions.

• Tactical: The backbone of a Battle Company, Tactical Marines are those who are flexible in combat, relying on both ranged weapons and melee weapons in combat. Note that due to the order of the Companies, they usually have served as both Assault and Devastator Marines, so they definitely know the basics of both, granting the majority of the chapter great theoretical tactical flexibility.

• Veteran: Veteran Marines are those who have seen through several centuries, allowing them access to all the cool toys in the Chapter's armory. They're hopefully experienced and cool-headed enough not to, say, super-glue the relic blade of the founder to the codpiece of their armor to skullfuck the enemies of mankind. Chapter veterans get to wear Terminator armor (the Crux Terminatus is a cross between a medal and authorization papers), but they sometimes stay with normally-sized power armor instead, which is instead slowly turned into Artificer armor by all the bling and enhancements. Power-armored Veterans are divided into two subgroups: Vanguard (who focus on close quarters combat) and Sternguard (who focus on bolter drills and other forms of ranged warfare).

The first company very rarely takes to the field as one collective company. Instead, the veterans are seconded to other companies, often serving as commanding officers and sergeants to other squads, so as to spread their experience and skill as widely as possible.

Ranks

The Codex Astartes formalized and simplified the ranks among the Adeptus Astartes, eliminating some ranks like "commander" and "lieutenant", while adding some more. They include:

• Chapter Master: The grand poobah of the Chapter. He is the one who gives Marine companies their assignments, and is under no obligation to recognize any external authority save for the God-Emperor of Mankind, though most Chapter masters will recognize and honor (if not obey) the authority of the Inquisition. A chapter master is not merely the commander-in-chief of the chapter, he is also expected to be an administrator, a paragon of martial skill, a councilor, a tactician, a strategist, and often even an admiral as a planetary governor, as the chapter master will typically have ultimate authority over the chapter's homeworld, or home fleet in the case of crusading chapters. Needless to say, chapter masters are some of the most formidable individuals in the galaxy, rivaled only by the greatest heroes and monsters of other races.

• Captain: Captains are the commanders of Companies, overseeing their Marines from the front line instead of the back. Captains are usually promoted from the senior Sergeant in the Company. The most senior is the First Captain, who commands the Veteran 1st Company, and is often the official heir apparent to the Chapter Master. Each Company Captain also holds a Chapter-level position of authority, supervising his Chapter's fleet, vehicle pool, recruits, or territory, for example.

• Sergeant: Sergeants lead squads of four to nine other Marines depending on the influx of recruits. There are approximately ten sergeants per Codex approved Company. Often, the most senior sergeant will be the commander of a company's "First Squad" (usually a Tactical Squad) and will likely be next in line for a promotion if the Captain is ever slain, but not always. Members of the Captain's Command Squad may also be Sergeants who get additional duties as the Captain's role might require.

• Veteran-Sergeant: Not a "rank" exactly, but more of a recognition of status for those who have been members of a Chapter's First Company, quite frequently these guys get redistributed back to the lower companies to act as squad leaders where their experience will do some good, hence "Veteran Sergeant". These guys will usually get to wear the "Crux Terminatus" even when in power armour, to represent the fact that they have earned the right to use Terminator Armour. Note that Veteran Sergeants can serve in the ranks of the Scouts, Devastators, and Assault Marines despite being technically overqualified, in each case helping the new recruits to adapt to Chapter life. In old 3rd Edition rules you could get Captains without terminator honours, which kind of implied that they never passed through the first company but still got command, nowadays a Captain is just one thing.

• Champion: Champion is actually a number of positions within a chapter, with each company having a champion, the chapter as a whole having a champion, and a champion being drawn from within the ranks of the honour guard to serve as the personal champion of the chapter master (though these last two positions are often held by the same marine). A champion is theoretically the best close quarters fighter in a company, charged with protection of the Captain from all threats. Given that your average Captain is a badass in power armor, this may seem redundant, but it's supposed to allow him to focus on coordinating the battle. One of the biggest dissonances between the crunch and fluff is manifested with the champions, in that on the tabletop officers are almost universally more formidable than the champions that are supposedly there to protect them. Also, rather hilariously, the current status of their chapter champion is one of the only breaks the Ultramarines have with the Codex Astartes, due to the raging ego of one Cato Sicarius.

• Force Commander: Not a rank but a title given to the commander of a task force (duh), either given if more than one company is fighting at the same time, or if the company has to split up and the Captain gives an XO like the leader of his command squad. For a tabletop comparison, this could be any senior sergeant since any character can be made the army's warlord and it would fit the description quite nicely.

• Honour Guard: Like a veteran-veteran, assumed to be the best of the best. These guys get bunched together and given some of the best gear available to the chapter. The fluff tells us that these guys are peers of Captains in terms of battlefield experience, but do not have the command rank to actually issue any orders, though when Honour Guard speak up it's advised that the officers nearby listen carefully. Thankfully the tabletop game is balanced not to give a whole squad full of Captain-equivalent soldiers.

• Standard Bearer: The Company Standard Bearer, given the title of Ancient (the old term for Ensign, who was traditional standard bearer), is charged with carrying and protecting the Company Standard, or banner. Also frequently joins the Command Squad. Should a Company Standard Bearer drop the banner and let it fall to the ground, he will essentially forfeit his honor. If the Standard Bearer should be killed and the banner stolen, then the entire Company will be dishonored until the banner is reclaimed. Which means that if you steal a Company Standard, you now have nearly one hundred Space Marines who were just trying to kill you, but now you had to go and make it personal. The most elite of these is the Chapter Standard Bearer (often a member of the Honour Guard), who carries the Chapter banner in war.

Outside of the above mentioned battle ranks, there are other senior positions within a Chapter:

• Chief Librarian: The head of the Librarium, who assigns Librarians to assist in battlefield communications. Also tests to see whether or not his battle-brothers are tainted by Chaos ("Yes brother, this is standard Codex procedure." *Snaps Latex gloves*)

• Master of the Apothecarion: The head of the Apothecarion, who assigns an Apothecary to each Company. The Apothecarion in turn also takes care of the gene-seed that Chapters place such holy emphasis on, and for good reason: no gene-seed - no new recruits. Also, considering the relatively practical and utilitarian approach marines take to science, Masters of the Apothacarion are some of the only actual scientists in the entire freaking Imperium, if you don't count the ones that pray to their own bionic elbows, which you shouldn't.

• Master of the Forge: The head of the Armoury, who assigns Techmarines to oversee maintenance of the machine-spirits of the chapter's wargear and motor pool. Their position often overlaps to some degree with the Chapter's Reclusiarch, given that both are responsible for keeping the chapter's relics in good condition, so many artifacts will fall under both of their duties. Again, given that their religious zeal is tempered by the practical mindset of a space marine, Masters of the Forge are some of the only engineers in the galaxy that are actually still innovating to any degree, which really shows when you compare the armories of the modern space marine chapters with their traitorous counterparts.

• Master of Sanctity: The head of the Chaplaincy, and spiritual leader of the Chapter. He assigns Chaplains to the Companies to oversee the spiritual health of the Chapter. This position is often, but not always, held by the chapter's Reclusiarch. Though it might be tempting to compare them to warrior bishops, they're actually atheists, seeing the Emperor as an honored predecessor and the epitome of humanity, but not a god.

• Reclusiarch: The Chaplain who oversees the Chapter's Reclusiam (where they keep the relics and other secret historical stuff). But quite often the job gets rolled-up into the Master of Sanctity's job description (particularly if the Chapter is relatively young and has not accrued entire millenia worth of trinkets). It's uncertain what interaction (if any) they have with the Master of Relics, or it is quite possible that a Chaplain receives the role if that Captain of the 9th company gets a different position. Or, maybe, the Reclusiarch looks after the more "holy" and historically significant relics, and distributes some of them to Chaplains to carry in battle, while the Master of Relics okays the deployment of precious but combat worthy stuff like ancient marks of power armour or Heresy-era tanks, as Master of the Forge is technically a specialist position, not an authoritative one.

• Lord Admiral: Often the Captain of the 4th company gets this position by default as "Master of the Fleet", but it's not unheard of for a Captain to step down from the position if someone else would be better suited to the role; they call that person "Lord Admiral", and he gets command over the Chapter's fleet assets. Though it might be perfectly reasonable that that space marine holds a battlefield rank of Battle-Brother or Sergeant, so he's probably just temporary until the Captain (or his replacement) wants the job back.

• Lieutenant Commander: In the days of the Great Crusade, these individuals commanded battalions of five companies, outranking Captains and were subservient to Chapter Masters. We know of only one example of this rank though it is uncertain whether the title holds the same authority as before. From what we know it now applies to the commander of a vessel, which makes sense since most Space Marine chapters have more ships than Captains, so somebody has to get the job of commanding them. Though often we assume it's just a techmarine or sergeant of whichever squad gets attached to that vessel or more likely a badass high ranking Chapter Serf who doesn't need to be superhuman to understand how spaceships operate.

Codex Skub

In case you haven't picked up on it yet, the Codex is rather controversial, for a number of reasons. First off, and perhaps most significantly, is the fact that even GW's own writers don't agree on what the codex is. Saint Abnett views it as a book of tips and strategies, comparable to The Art of War. Graham McNeill (the guy who wrote the Ultramarines Omnibus) sees it as a comprehensive but inflexible guide to strategy, organization, and conduct. Matt Ward quite famously sees it as a literal Space Marine Bible, a holy book that all marines follow to the letter. Like a lot of GW lore, the canon is up in the air, and as such it's kind of open to interpretation. When it comes down to it, most of the argument over the codex comes down to people saying, "The Codex is a detrimental, absurd tome written by an OCD faggot, that only serves to weaken the Imperium!" and others saying, "The Codex is one of the most important things in the entire imperium, setting down the rules that have allowed it to survive to the modern day!" Both people are correct because of the nebulous canon. Many writers are clearly very critical of the Codex, and portray it as antiquated and damaging, whereas others portray it as comprehensive and useful, but increasingly antiquated. Also there's Ward, but let's not talk about him. Which version is true? Yes.

It's also worthy of note that many people within the Ultramarines take the Codex with a grain of salt. Captain Titus, Uriel Ventris, and even Marneus Calgar and the freaking primarch himself have all been critical of the codex at various times, or rather, been critical of people's reception of it. All of these people see the codex as useful and important, but take issue with people, Ultramarines or otherwise, that see it as a holy book that contains everything you need to know. Perhaps Guilliman himself put it best, saying, "[My teachings] are yet flawed. No one, not even one such as I, can anticipate every possible outcome of battle. My words are not some holy writ that must be obeyed. There must always be room for personal initiative on the battlefield. You and I both know how one spark of heroism can turn the tide of battle. That knowledge and personal experience can only be earned in blood, and the leader in the field must always be the ultimate arbiter of what course of action should be followed." As the opening quote implies, Captain Titus is also quite critical of Leandros's interpretation of the codex, pointing out that personal initiative is just as important as adhering to the codex. Then again, Titus is also quite clearly a company champion who got mixed up for a captain, what with his disregard for tactics in favor of glorious melee, so maybe we should just ignore what he thinks.

Ultimately, your own take on the codex is going to depend on a number of things, including whose canon you believe, you opinion of the Legions, your opinion of Guilliman, and a dozen other things, just decide for yourself. Don't let yourself get pulled in by the fanboys saying the Codex is the perfect guide to everything, and conversely don't listen to the idiots who say the Codex is only useful as toilet paper.

"Codex" Chapters with doctrinal variations

More commonly, are those chapters which follow the codex at an organisational level, but disregard certain tactical aspects contained within, most likely because they have their own modus-operandi that they have a preference for, or because they create their own unique tactics that had never been considered.

Aurora Chapter

• Follows the Codex Astartes, yet has a large number of vehicles.
• They have a lot of vehicles.
• For a 1000 man sized Chapter, they have a lot of tanks.
• Of all the Codex Chapters they have the most tanks.
• Their armored spearhead attacks are pretty devastating.

Charnel Guard

• Cannot say too much about those guys since they are very secretive, thus their organisation and structure are completely unknown.
• Rumored to be Blood Angels successors, yet as said before, they are totally unknown from a organisational and structural P.O.V.
• Have a lot of Great Crusade and Horus Heresy Era stuff, including a Fellblade.

Crimson Fists

• More tactically oriented Imperial Fists.
• Actually do follow the Codex more closely than other Sons of Dorn (but not that much like the Hammers of Dorn).
• At the time of their founding, they were known to be the most level-headed members of the Imperial Fists Legion, therefore took in the Codex much faster and easier.
• Only deviation is the existence of a Crusader Company that is a 1st Company that has 128 Veterans. A result of an event where they were reduced to 128 members during the Crusade of Righteous Liberation.
• Due to the whole situation with Rynn's World, the Chapter became very capable at fighting Orks.

Emperor's Shadows

• Iron Hands Successors that follow the Codex.
• Put more emphasis on projectile weapons (like Bolter Weapons) and Dreadnoughts.

Executioners

• Choose to go into close combat with the enemy.
• Heavy emphasis on their own skills and superhuman abilities enhanced with sheer Determination.

Hammers of Dorn

• Follow the Codex to the letter, yet do put more emphasis on heavy weapons and overwhelming firepower.
• No really, they follow the ABSOLUTE LETTER of the codex.
• Not even the Ultramarines(Famous for having the primarch that wrote the damn thing) follow the codex more rigidly than them.
• They probably actually read the Codex from cover to cover.

Hawk Lords

• Codex compliant, yet put large emphasis on flyers.

Minotaurs

• Instead of sending out a single company, the Minotaurs utilize mob and berserker tactics along with sending out all ten of their companies to utterly overwhelm and crush their foes.

Raptors

• Camouflage Power Armour. Technically this IS in the codex, but they're the only space marine chapter out of literally thousands that actually bothers to do it. They're also sneeki beekies, just like their Raven Guard progenitors.

Raven Guard

• Sneeki Cheeki Beekies. While they do follow the codex, their chapter made amusingly extensive use of mutants (during the Horus Heresy), and stealth tactics and guerilla warfare due to their situation.

Space Sharks/Carcharodons

• Greater emphasis on infantry and terror tactics.
• Will sneak up as close as possible to the enemy to later tear them a new one in close combat while berserking.
• May be organisationally non compliant as well, but they are quite tight lipped about it.

Storm Giants

• Codex compliant, but utilize armoured assaults, Drop Pod strikes, and heavily use Scouts to get intel before ruining someone's day.
• Due to their heavy use of Scouts, they have a larger than average 10th Company.

White Scars and some Successors

• Disproportionate emphasis put on bikes and speeders compared to heavy vehicles, still adhering to codex formation however.

Chapters with differences in formations or composition

Some chapters have taken the idea of a "Chapter" and tweaked it with their own unique spin on its organization, either by adding units or ranks that aren't found anywhere else, or have their own composition of companies that doesn't fit with the approved codex model. In some cases they may ignore the codex altogether and do their own thing.

Black Dragons

• Dragon Claw squads, made up of mutants who make use of adamantium coated wrist blades.

Blood Ravens

• Pre-Aurelian Crusade:
  • Usually, the Chapter Master was the Chief Librarian too, like Azariah Kyras. This tradition of Chapter Master/Librarian combo started with Azariah Vidya (as in Vidya Games).
  • Their gene seed causes them to have an above average number of Librarians, so many they can field two whole squads of them in the First Company. Librarians are so recurrent among Blood Ravens that it's not uncommon for one to be even a Captain.
  • Actually Codex Compliant in structure, yet utilize their Librarians to scry and predict the movements of their enemies (so their Scouts are Librarians too?) and use the intel to formulate a counter strategy (because they appeared in Dawn of War, their way of war is an emulation of how RTS gamers play when they are serious).
  • Non-standard patterns of speech, incidents of hairesy, compulsive kleptomany and emphasis on devastating, defensive deepstrikes.
• Post-Aurelian Crusade:
  • With Gabriel Angelos, a non-psyker, taking the position of Chapter Master they returned to a more codex-compliant organization, albeit severely undermanned.

Blood Angels and Successors

• Scouts graduate to Assault Squads rather than to Devastator squads.
• The use of non-standard tech, like Baal Predators, Furioso and Librarian Dreadnoughts.
• Sanguinary Priests (Apothecaries) make up part of the chapter priesthood equivalent to Chaplains, who are busy tending to...
• ...The Death Company.

Dark Angels and Successors

• The Deathwing & Ravenwing instead of First and Second companies.
• Inner Circle in place of usual chapter command structure.
• Chaplains taking the additional role of Interrogators.
• Battle Companies incorporate an additional squad of veteran marines.
• Some nifty STC that they do not share with anybody apart of their own successors.

Exorcists

• Have two additional scout companies to account for the high attrition rate amongst recruits.
• ...said attrition rate being caused by subjecting recruits to daemonic possession.

Iron Hands

• Have a Chapter Council instead of a fixed Chapter Master, though a leader may be nominated.
• Chaplain Techmarines, aka "Iron Fathers".
  • The current leader is thus a Chapter Master Chaplain Techmarine. And people say the Blood Ravens are the crazy ones.
• Terminator Armour was distributed to squad sergeants instead of being reserved only for the First company.
• Pre-6th Edition fluff indicated that individual companies (clans) had their own veterans and recruits, newer fluff put them more in line with the Codex.

Iron Snakes

• Instead of having five regular battle companies and five reserve companies, the Iron Snakes have ten battle companies with an equal number of veterans, regulars and neophytes for perfect balance.
• Each squad has a Apothecary, personal Squad Standard Bearer and a number of specialists of their own.

Red Scorpions

• Apothecaries act in squad command roles instead of sergeants.

Salamanders

• Have seven oversized companies instead of ten, but otherwise broadly conform to the codex.

Star Phantoms

• Each company takes a Devastator Squad over a Tactical Squad, leaving five Tactical and three Devastators in the battle companies
• The chapter is never at full strength, seldom even at half, but maintains weapons as though they were. Their "tactical" reserve companies can fill in for full devastator squads, if needed.

Storm Wardens

• Tempest Blades being a non-codex formation.
• Heavy emphasis on mechanized warfare and mano-a-mano honorable duels to the death.

Ultramarines

• Tyrannic War Veterans are a non-codex formation.

White Consuls

• Have two Chapter Masters instead of one

Non-Codex Chapters

As mentioned, there are so many chapters in the Imperium and very few of them follow the codex absolutely to the letter. Many chapters have their own preferred mode of warfare based upon their experiences, supplies and dispositions, often they generate their own interpretations and deviations from the codex. Here follows a comparative listing of those chapters and the way in which they differ from what the codex actually prescribes.

Astral Claws

• Pre-Red Corsairs Times: Before Lugft Huron went pants-on-heads retarded, the Chapter was known for being exceptionally stubborn with skilled Bikers and favoring lightning strikes and boarding actions while still following the Codex.
• Badab War Times:
  • Due to Huron's pants-on-heads retarded thinking, the Chapter seized the Badab Sector's industry and made it so that Bolter rounds and Rhinos were mass-produced to the point being expendable, not to mention the larger-than-standard number of marines due to them purposefully not paying their geneseed tithe.
  • Emergence of specialized units (such as the hated Corpse-Takers) and human Auxilia. Squads larger due to aforementioned not paying of the geneseed tithe.

Black Templars

• "Chapter" made up of ad-hoc crusade fleets and fighting companies, their numbers thus swelling up to six times the size of everyone else's.
• No Scout company, instead recruits are apprenticed to fully fledged battle-brothers, aka "Crusader squads".
• No Librarians.
• Doctrinal emphasis on close quarters combat.
  • Abundance of previously unsanctioned Land Raider "Crusader"s to deliver said Crusader squads to CQC. See the trend here?
• May or may not deify the Emperor. The canon is kind of up in the air right now.
  • The position of "Emperor's Champion", a Chapter Champion-esque title but of faith significance.

Grey Knights

• Due to their unique training and equipment (not to mention the intimidatingly insane shit they have to deal with), the Codex would actually hamper them instead.
• All psyker Chapter of Demon hunting marines. Nuff said.
• The infamous Dreadknight.
• When the Neophyte ends his training, he becomes a battle brother and is issued a suit of power armour and his standard wargear.
• Do not have any artillery weapons like Whirlwind Artillery Tanks or lack of certain vehicles other Chapters have.

Legion of the Damned

• Previously Codex adherent Fire Hawks (maybe, now it's uncertain if they are Fire Hawks or somebody/something completely different), now a horde of angry hellfire powered, space/time/dimension travelling, spectrerevenantdemonspacemarines.
• Utilize more powerful, but unstable early versions of existing Imperial Weapons like early Horus Heresy Era Plasma Weapons.

Space Wolves

• Ignore the organizational parts of the codex outright. It would be easier to go their page to find out how they are organised.
• Simply put, Leman Russ wanted them to be forged in his vision instead that of Roboute Guilliman.
• Although they do however take some useful tactics from the codex because they like them, they see them as just that: useful tactics, and nothing more.
• Fenrisian Wolves/Thunderwolves used by the Chapter. This may or may not be heresy.
• Have more than a thousand marines, yet not that much as the Black Templars.
• Threw the typical training process out the window because of the Canis Helix.
• In the previous editions, they had access to Leman Russ tanks (since the tank was named after their Primarch).
• Wolf Priests combine both Chaplain and Apothecary roles.

Purpose for Gamers

Of course, there's a reason Games Workshop included the Codex Astartes in their fluff (long before Matt Ward came along, by the way). Basically, it makes it easier for players to invent their own Chapters.

Players who just have an idea for a cool color scheme or name but don't want to put any effort into making up a whole organizational layout can just make a Chapter that rigidly follows the Codex, like the Ultramarines. Those who want to have one or two unique organizational or tactical features can make a Chapter that generally follows the Codex but has some variances, like...well, most of them (see above). And players that want to make up entirely independent structures themselves can make Chapters that ignore the Codex entirely, like the Space Wolves or the Black Templars.

This means that Matt Ward's Codex worship isn't just lame, but actually bad for GW's business: By telling players that only Codex Chapters are any good, he's discouraging players with their own ideas from investing in models, paints, tournaments, and maybe even later editions of the game. Truly, there is no end to his failure.