Codex

A Codex is a publication of Games Workshop that details the units and models each army in the Warhammer 40,000 tabletop miniatures game can use in a game. The name is based on the Codex Astartes, the tome written by Roboute Guilliman, the Ultramarines Primarch, detailing how a Space Marine Chapter should be organized. Codexes follow the same edition publication history as the Warhammer 40,000 tabletop game itself.

1st Edition
The 1st Edition of the game is referred to as Rogue Trader, it was when Games Workshop brought out futuristic models in 1987 that turned out to be Space Marines except with wierd pointed faces. This went on for a while and many people loved building these Space Marines so the Games Workshop hobby magazine, White Dwarf, started making army list and devising strategies for people to use in these Rogue Trader games. New models were soon released by games Workshop for the line and the many people who had always enjoyed Warhammer Fantasy were now thrilled at the idea of Warhammer 40,000, which was essentially a science fiction, or more properly a science fantasy, setting with many of the same tropes and elements as its dark fantasy counterpart.

2nd Edition
The 2nd Edition of Warhammer 40,000 was released in 1993 and greatly expanded the number of factions and armies that could now be played. The release of this edition was marked by the production of boxed starter set containing Ork and Space Marine models with dice and a rules book. The animating idea behind this edition of the game was to provide more opportunities for players to participate in larger battles. Also special characters were introduced to replace the older concept of battlefield heroes. New rules were also provided for the use of psychic powers which were essentially the equivalent of the magical system deployed in Warhammer Fantasy. True codexes as they later became known to fans of the game were still not available early this edition, but the army lists and background information for Warhammer 40,000 printed in White Dwarf became far more deeply detailed. Later in the edition's publication run, Games Workshop introduced the first Codexes for each of the playable faction's armies, though they were far smaller and contained a great deal less fictional background information (what fans refer to as "fluff") than the Codexes of later editions.

3rd Edition
The 3rd Edition of Warhammer 40,000 was released in 1998 and like the 2nd Edition, concentrated on streamlining the rules for larger battles. The rulebook was available alone, or as a boxed set with miniatures of Space Marines and the newly-introduced Dark Eldar. The 3rd Edition soon introduced Codexes for each of the major factions in the game, releasing revised editions of each of these Codexes between 2003 and 2004. Towards the end of the 3rd Edition, four new army codexes were introduced: the xeno (that is, alien) races of the Necron and the Tau and two armies of the Inquisition: the Ordo Malleus (called Daemonhunters), and the Ordo Hereticus (called Witchhunters); elements of the latter two armies had appeared before in supplementary material (such as Realm of Chaos and 2nd Edition's Codex: Sisters of Battle). At the end of the 3rd Edition, these Inquisition armies were re-released with all-new artwork and army lists. The release of the Tau coincided with a rise in popularity for the game in the United States. The following Revised Codexes were released for the 3rd Edition.
 * Daemonhunters (March 2003)
 * Dark Eldar (November 2003)
 * Necrons (July 2002)
 * Space Wolves (April 2000)
 * Witch Hunters (April 2004)

4th Edition
The 4th Edition of the game was released in late 2004 and the Revised 3rd Edition Codexes were used until the release of the 4th Edition Codexes between 2005 and 2008. This edition did not feature as many major changes as the prior editions, and was "backwards compatible" with each army's 3rd Edition codex. The 4th Edition was released in three forms: the first was a standalone hardcover version, with additional information on painting, scenery building, and background information about the Warhammer 40,000 universe. The second was a boxed set, called Battle for Macragge, which included a compact softcover version of the rules, scenery, dice, templates, and Space Marines and Tyranid miniatures. The third was a limited Collector's Edition. Battle for Macragge was a "game in a box," targeted primarily at beginners. Battle for Macragge was based on the Tyranid invasion of the Ultramarines' homeworld, Macragge, during the First Tyrannic War. An expansion to this was released called The Battle Rages On!, which featured new scenarios and units, like the Tyranid Warrior. The following Codexes were released for the 4th Edition.
 * Black Templars (November 2005)
 * Chaos Daemons (May 2008)
 * Chaos Space Marines (September 2007)
 * Dark Angels (March 2007)
 * Eldar (November 2006)
 * Orks (January 2008)
 * Tau Empire (March 2006)

5th Edition
The 5th Edition of Warhammer 40,000 was released in the summer of 2008. While there are some differences between the 4th and 5th Editions, the general rule set shares numerous similarities. Codex books designed prior to the 5th Edition are still compatible, with only some changes to how those armies function. The replacement for the previous edition's Battle for Macragge starter set is called Assault on Black Reach, which features a pocket-sized rulebook (containing the full ruleset but omitting the background and hobby sections of the full-sized rulebook), and starter Ork and Space Marine armies. Each army contains an HQ choice, either an Ork Warboss or a Space Marine Captain. The following Codexes have so far been released for the 5th Edition. [[Category:C]]
 * Space Marines (October 2008)
 * Imperial Guard (May 2009)
 * Space Wolves (October 2009)
 * Tyranids(January 2010)
 * Blood Angels (April 2010)