Codex Astartes

Overview
"We follow in the footsteps of Guilliman. As it is written in the Codex, so shall it be."


 * -Marneus Calgarr, Chapter Master of the Ultramarines

The Codex Astartes is a mighty tome of military organization, strategy and tactics written by Roboute Guilliman, the Primarch of the Ultramarines, to prevent another Horus Heresy. It outlines Guilliman's ideal for the moral behaviour, order of battle and tactical doctrine of a Space Marine Chapter. While not all Space Marine Chapters in the Imperium adhere to the Codex's dictates with the same rigidity as the Ultramarines, most obey the spirit of the Codex if not the actual letter. A Space Marine Chapter that generally follows the guidelines of the Codex Astartes is generally referred to as "a Codex-compliant Chapter."

History
The Horus Heresy had revealed previously unknown genetic weakness in the gene-seed of the Primarchs and Space Marines among the original 20 First Founding Space Marine Legions, weaknesses that left the Legions in question greatly exposed to corruption by the Ruinous Powers of Chaos. This risk was exasperated by the rapid nature of Space Marine recruitment during the centuries between the Great Crusade and the outbreak of the Horus Heresy itself. With the Imperium of Man expanding so quickly across the galaxy during the Great Crusade, the need for fresh recruits in the Space Marine Legions was great. So much so that some Legions had not been as particular in their gene-seed screening practices and recruit selection processes as theyshould have been. The first objective of Roboute Guilliman in writing the Codex Astartes was to both recognise and purge these weaknesses.

Following the end of the Horus Heresy and the retreat of most of the Traitor Legions into the Eye of Terror, the Codex decreed that the nine remaining Loyalist Legions would be divided into 1,000-man Chapters, the Chapter Masters of which would be directly beholden to the Emperor himself and no other, not even the Primarchs of their original founding Legions (save in the case of the single Chapter that would remain under each Primarch's control and retain its Legion's original name). No one man in the Imperium could ever again control the superhuman might of an entire Legion of 10,000 or more Space Marines.

The Codex outlined a new, more measured process, for Space Marine selection and recruitment and insisted that each newly-created Successor Chapter would tithe 5% of its genetic material to the Adeptus Terra and the Adeptus Mechanicus for testing and monitoring. It also decreed that only the Emperor himself, through the auspices of the High Lords of Terra, would ever again be able to order the creation of a new Space Marine Chapter. All gene-seed would be subjected to the greatest genetic scrutiny before being used in the creation of new Space Marine implants. To prevent cross-contamination, the Codex rebuked the practice of sharing gene-seed between different Chapters and, henceforth different Legions with their different genetic make-ups. From then on, each Chapter would have to rely solely on the gene-seed produced in the bodies of its own Marines.

The Codex also further defined the accepted tactical doctrine, Chapter organisation, order of battle, and recruitment practices for a Space Marine Chapter. It explained the different battlefield roles assigned to each squad of Space Marines in a Chapter, defining them as Tactical, Assault or Devastator Squads and assigning different equipment and purpose to each (see the excerpts below).

There were many other topics covered in the Codex and all of them displayed Guilliman's formidable intelligence and hard-won wisdom. The most controversial and yet most important of the topics and decrees made in the Codex Astartes was that the original twenty Space Marine Legions consisting of 10,000 Marines each must be broken down into the smaller organisations known as Chapters, each Chapter to consist of ten companies of 100 Space Marines. The breaking of the remaining nine Loyalist Legions into multiple Space Marine Chapters is known to Imperial historians as the Second Founding.

Only one of the original Space Marine Legions, the Space Wolves, has never been broken down into the ten companies decreed in the Codex Astartes. The Space Wolves continue to organize their forces into thirteen 'Great Companies', different in organization to those specified by the Codex. Note that the oldest copy of the Codex, the Apochrypha of Skaros, refutes the commonly-held belief that the Space Wolves have never broken down into separate Chapters, stating that two Second Founding Chapters were created from the Space Wolves (Index Astartes I, pg. 13). However, the Space Marine Codex 5th edition lists only one Second Founding successor to the Space Wolves: the Wolf Brothers, who were disbanded at an unknown time in the past because of extreme gene-seed corruption and mutation.

Excerpts
"Let them bestride the galaxy like the gods of old. Sheltering Mankind from destruction at the hands of an uncaring universe."

--Roboute Guilliman, as laid down in the Apochrypha of Skaros. (Space Marine Codex 5th edition)

"Consider the magnitude of your duty at leisure, but act with hesitation when action is required."

--Roboute Guilliman, as laid down in the Codex (Space Marine Codex 3rd edition, "Legio Astartes Daily Rites").

"The warrior who acts out of honour cannot fail. His duty is honour itself. Even his death -if it is honourable- is a reward and can be no failure for it has come through duty. Seek honour as you act, therefore, and you shall know no fear."

--Roboute Guillliman, (Space Marine Codex 4th edition)

"They shall be pure of heart and strong of body, unsullied by doubt and untainted by self-aggrandizement. They will be bright stars in the firmament of battle. Angels of death whose swift wings bring extermination to the enemies of man. So it shall be for a thousand times a thousand years, unto the end of eternity and the extinction of mortal flesh."

--Roboute Guilliman, (Ultramarines Codex 2nd edition)

"As you are a knight in service of the Emperor, so is the Rhino your steed. Honour it, respect it, see that its needs are met, and it shall serve you well through all the battles you must face."

--Roboute Guilliman, as laid down in the Apochrypha of Skaros (Space Marine Codex 5th edition).

"Of the Tactical Space Marine, bedrock of his Chapter and paragon to his brothers, I shall tell thee. 

''He shall be steeped in the lore of battle and schooled in all manner of weapons and strategy. With combat blade, boltgun and grenade shall he assail the foe. But these are mere tools: a Tactical Marine's true weapons are his courage, his wits and his dedication to his brothers. ''

''He will bring the foe to battle in a manner and time of his choosing, never himself caught unready or ill-prepared for the task at hand. In defence he shall be as stalwart as the mountain, a bulwark stood firm against the enemies of Man. In attack he shall strike with the wrath of the Immortal Emperor, felling the foe without mercy, remorse or fear."''

--Roboute Guilliman, as laid down in the Apochrypha of Skaros (Space Marine Codex 5th edition).

"And of the Assault Marine so do I decree: 

''He shall descend upon the perfidious foe as an Angel of Judgement from on high. Let the jump pack be his wings and the roar of its engines a hymn of retribution. ''

''Let the chainsword be his sceptre of decree, its harsh voice singing joyfully with each and every blow. With it shall the Assault Marine bring bloody retribution to the heretic, the traitor and all alien transgressors who trespass on the Emperor's domains. ''

''So will the Assault Marine be the hunter of warlords and the slayer of kings. His armour shall run slick with the life blood of the vanquished, and all shall honour his name".''

--Roboute Guilliman, as laid down in the Apochrypha of Skaros (Space Marine Codex 5th edition).

"A Devastator's reach shall be without limit and his touch without mercy. Fire shall roar from his fingertips, but it shall consume him not. Thunder will roar when he calls, yet it will swallow him not. 

''Let the Devastator Squad be thy blazing wrath, bringing the light of the Emperor's justice to the darkest corners of the battlefield. Wherever he stands, that shall be his fortress of righteousness. He shall hold in his gift the fate of all who pass before his unblinking gaze. ''

All shall fear him, and he shall fear no one."

--Roboute Guilliman, as laid down in the Apochrypha of Skaros (Space Marine Codex 5th edition).

"Use your Bike Squad as a blade, striking the enemy and turning aside his counter-blows in equal measure. But in all things beware that speed is nothing without direction, just as even the mightiest weapon is worthless without careful aim. 

''A Biker's stance should always be resolute and dauntless, but never immobile or rigid. Speed is his advantage, and suprise his deadliest weapon. In fluidity he will find success and in success shall he find renown."''

--Roboute Guilliman, as laid down in the Apochrypha of Skaros (Space Marine Codex 5th edition)

"As a commander your tools and devices shall be myriad, yet the wise man knows that battles are won by flesh, not the machine. Flesh can learn, whilst the machine must be forever instructed. Flesh knows loyalty to its brothers and veneration of its Emperor, whilst the machine knows not these things. 

''Whenever the day is darkest and victory in doubt, look not to the machine for aid, but to your Battle-Brothers. The machine can only bring victory if you tell it how such a thing can be done. Your brothers will walk through fire, they will stride through the most terrible carnage at a single word from your lips and they will bring you victory simply because you ask it of them."''

--Roboute Guilliman, as laid down in the Apochrypha of Skaros (Space Marine Codex 5th edition)

"Make the Predator's virtues your own. Let your resolve become as impervious as the Predator's armoured hull and let your rage strike with the righteous fury of its guns. As it crushes the foe beneath its remorseless advance, so shall you smite the traitor and the alien without hesitation or regret.

''Know that to take the field alongside a Predator is to fight at the side of one of mankind's most honoured guardians. To strive with less than your all beneath its Iron Gaze is to dishonour yourself and your Battle-Brothers before one of mankind's greatest heroes."''

--Roboute Guilliman, as laid down in the Apochrypha of Skaros (Space Marine Codex 5th edition)