The Codex Astartes is the holy tome written by Ultramarines Primarch Roboute Guilliman. It defines the organization and tactical doctrine of the Adeptus Astartes and is followed by many, if not a majority, of Space Marine Chapters.
Guilliman is undisputedly one of the greatest military minds in history, rivaling if not surpassing all of the other Primarchs. The Codex Astartes is considered one of Guilliman's most influential works.
Yet there is a schizophrenia in the 40k universe...
The Codex Astartes was a work written by one of the greatest strategic minds in the universe, designed to cover every possible situation . . . and yet, one of the most common ways to portray genius in the 40k universe is to have your protagonist not follow it. Or, in the most extreme cases, actively reject it.
For example, take this guy:
http://2.bp.blogspot.com/-3-JHE8HrpJ...Honour_Art.jpg
Captain Uriel Ventris of the Ultramarines. The Ultramarines, Roboute Guilliman's own chapter, are the epitome of the Codex Astartes. Yet what distinguishes Captain Ventris as a protagonist?
Uriel Ventris is a flexible military commander who due to the efforts of his mentor, Captain Idaeus, learned to think outside the confines of the Codex Astartes, the masterpiece of Roboute Guilliman and the manual of war that most Space Marine Chapters base their tactics, strategy and organization upon. [emphasis added]
Article on Uriel Ventris, from the Warhammer 40k Wiki
Those who follow the Codex, such as Sergeant Learchus in particular and the rest of the Ultramarines in general, are presented as inflexible and unimaginative.
The Codex Astartes (hereafter CA) is portrayed like a strait-jacket, and everyone who follows the "textbook" is always outsmarted by someone who doesn't follow it, and therefore thinks "outside the box". But the CA was written by the most brilliant commander of the Adeptus Astartes. I would have to think that someone doesn't get to be called that unless he does think outside the box. The CA should, by definition, discuss tactics that are outside the box. It should praise initiative, imagination and adaptability.
So who are these "inflexible", "unimaginative" guys who follow the CA?
Space Marine Captains:
Space Marine Captains are masters of the battlefield, able to read its ebb and flow as ancient mariners would judge the changing of the sea. It is not enough for a Captain to simply be a skilled fighter in his own right...he must also have a superhuman grasp of strategy and tactics, as well as the will to employ them in the ever-changing arena of warfare.
Codex: Space Marines, Matthew Ward, 2008, p54.
Chapter Masters:
With the merest glance, a Chapter Master can appraise a warzone, can see every threat and every opportunity presented by the shifting lines of battle and divine how victory can be assured.
Codex: Space Marines, Matthew Ward, 2008, p52
Marneus Calgar:
Since rising to the rank of Chapter Master, Marneus Calgar has employed his flair for tactics and strategy in campaigns without number.
Calgar is a proud man, a trait that has earned him more than a fair share of enemies within the Imperium's internecine politics. Yet he also possesses a shrewd self-awareness that prevents pride turning sour and leading him into arrogance.
Codex: Space Marines, Matthew Ward, 2008, p84.
Commander Dante:
"
To his fellow Chapter Masters, Dante is an exemplar of the fearlessness, dedication, and strategic genius that speak to the heart of the Space Marines' never-ending mission." [emphasis added]
Codex: Blood Angels, Matthew Ward, 2009, p53.
Yet a common theme in the 40k universe is that the protagonist is a radical somehow, in that they go against the grain and rebel against the "rigid doctrine of the CA." Those that follow it are invariably portrayed as unimaginative automatons. The problem is with this line of reasoning is that if all the smart people feel that the CA is a rigid doctrine useful for only the unimaginative, then why is the CA held in such high regard? Why was Guilliman considered a genius, if the best he could do was write a book on doctrine that is only useful when your enemy is an idiot?
http://4.bp.blogspot.com/-Ytr5xDU_CX...l_Kopinski.jpg
Calgar follows the Codex? Idiot.
Guilliman believed in rigid structure and hierarchy and had a firm battle doctrine from which his Legion never wavered. He was in the process of documenting the "correct" tactics and operation of a Space Marine force, tried and tested during his long years of command, and suggested that the young Alpha Legion should adopt this "Codex" behavior. However, this attitude was anathema to Alpharius' belief in initiative and adaptability, and a heated debate over tactics and ideology ensued.
p56, Index Astartes: Alpha Legion, White Dwarf 276.
Granted, the article is written to present the Alpha Legion in a favorable light (in terms of badassery, not necessarily "goodness"). So, to emphasize Alpharius' awesomeness, you have to make Guilliman look like a rigid stick-in-the-mud. I'm sure that in reality Guilliman valued initiative and adaptability too, and put that in the CA. I mean, if he did put values like initiative and adaptability in the CA, there would have to be a Chapter out there that follows the CA and is well known for its initiative and adaptability, wouldn't there?
http://3.bp.blogspot.com/-m1mqeprom5...cal_Marine.jpg
Yup.
The distaste that people have against the Codex is really distaste against any sort of doctrine at all. In military fiction, whenever one wants to portray a protagonist as superior, one simply states that whatever action the protagonist takes is superior, and then declares that it goes against established doctrine. Everyone knows that doctrine is something written by a bunch of crusty old generals who haven't seen a battlefield in decades.
But Doctrine is actually a good thing.
Most readers of military history don't understand doctrine and don't want to, because it has no place in the tales of individual soldiers or great military leaders that they are used to. Indeed, doctrine is often seen as an unnecessary encumbrance that loses battles and gets in the way of exercising creative command. This is ironic, in that one of the prevalent goals behind doctrine is the simplification and streamlining of command, precisely so that commanders can fashion appropriate solutions during battle.
. . .
The development of doctrine is the natural imperative of any military trying to rise above the level of being merely an armed mob. It is an essential means by which militaries compensate for the negatives of warfare by building a certain measure of automatic behavior into the organization. Indeed, in the terrible crucible of combat, under the enormous pressures created by mass violence, doctrine is sometimes the only thing that holds forces together and allows them to continue fighting. By setting out a coherent set of tactical goals, units can continue to operate even if the chain of command is disrupted or destroyed.
Shattered Sword: The Untold Story of the Battle of Midway, Parshall and Tully, 2005, p82-83.
Combat veterans frequently say that one of two things saved their lives in combat: their training, or the guy next to them. Training is doctrine. The Army has an entire command devoted to it:
The United States Army Training and Doctrine Command, or TRADOC. Its whole purpose is to train soldiers and develop doctrine, in order to keep US soldiers from getting killed.
Ultimately having a maverick protagonist who rages against the system and succeeds against overwhelming odds while spitting in the face of established wisdom makes for a good story. In reality, in the chaos of battle, when a commander goes against established doctrine, the result is almost certainly disaster.
In short, the Codex Astartes really is a good book that has some worthwhile stuff in it. But if you decide to go against the Codex Astartes, you should take a long, hard look in the mirror. If you see this:
http://1.bp.blogspot.com/-XsoPavR1fK...pero_burns.jpg
You're probably ok. If you see something else...I'd stick to the Codex.