Each Imperial Guard regiment is raised from a single world and numbers between five hundred and ten thousand fighting soldiers, supported by a huge array of light and heavy armoured vehicles. Each regiment also has its own entourage, consisting of support staff, camp followers, suppliers, tech-priests, doctors, religious leaders and the like.
Regiments are drawn from all types of planets of the Imperium from Holy Terra to Feral and Medieval worlds, and the contributions of some planets over the ten thousand years of the Imperium runs into the billions, if not more. The Imperial Guard are constantly at war, freeing worlds from Chaotic or alien influence, or defending them from the same. The Imperial Guard rely upon the Imperial Navy for transport to and from warzones.
The Imperial Guard, first introduced in White Dwarf 109, was bound by a series of rules relating to its command structure. Squads of units formed platoons under a command squad. Units that were separated from the command squad were more limited in action. The initial Imperial Army could include, besides the basic squads, Rough Riders (a form of mounted trooper), penal troops, human bombs and Abhumans (see below). Vehicles were limited to Rhinos, and Land Speeders.
The first incarnation of the Imperial Guard as a fully-supported army was in 1995, with the release of the Codex: Imperial Guard sourcebook for the second edition of Warhammer 40,000. This was the first time that the army itself had specific army rules collected in their own sourcebook. With the release of the third edition of the game, almost all the Warhammer 40,000 armies eventually had new codices compatible with the new edition. In line with this, Codex: Imperial Guard was released in 1999, followed by Codex: Catachans in 2001. This was a smaller sourcebook (or mini-dex/mini-codex) that was meant to be used in conjunction with the "parent" Codex: Imperial Guard. The mini-dex itself provided even more specific rules for fielding one of the more popular Imperial Guard sub-armies, the Catachan Jungle Fighters, for which plastic models were available. In 2003, Games Workshop conducted the Eye of Terror worldwide campaign and released a corresponding sourcebook, Codex: Eye of Terror. This campaign sourcebook contained various rules, including a specific army list for another one of the Imperial Guard's notable sub-armies, the Cadian Shock Troops. Soon after the campaign ended, the changes in the Cadian Shock Troops army list were integrated into the Imperial Guard rules, and Games Workshop released a second, revamped version of Codex: Imperial Guard. To date, there has not been an official fourth edition ruleset version of Codex: Imperial Guard, although Games Workshop has stated that the latest codex is completely compatible with the newest version of the Warhammer 40,000 rules.
It was mentioned in White Dwarf issue 342 that a new Imperial Guard codex is in development and will feature "more tanks. A lot more tanks."
Because of the low in-game points cost of each individual Imperial Guardsman, Imperial Guard armies are capable of fielding a much larger number of troops than most other armies. In addition, they have access to various vehicles, such as the Leman Russ main battle tank, Basilisk mobile artillery, Chimera armoured troop transport and the Sentinel scout walker.
In the latest Codex, many "doctrines" allow Imperial Guard regiments to become much more varied, allowing players to, for example, make their troops more effective in close-quarters combat, upgrade their armour, or utilise special troop types.
In addition to humans, the Imperial Guard also contains several types of abhumans—species evolved from humans that differ markedly from the norm. The two species most commonly found are the Ogryns (the counterpart of the Warhammer Fantasy setting ogres) and the Ratlings (the equivalent of the halfling/hobbit).
The Imperial Commissar, as described by many Warhammer novelists, is given complete jurisdiction to judge the actions of any trooper or officer and to act accordingly. An Imperial Commissar's word is immutable law and his visage is one of grim authority that is to be respected and rightly feared, reporting to The Commissariat personally.
Using the above-mentioned doctrine rules, some regiments field Grenadiers which are specialized members of the same Imperial Guard regiment that have received specialist training and equipment. In-game, Grenadiers are represented by the same unit profile as Stormtroops and perform a similar function, although they are completely different in background terms.
In the background literature, Stormtroops do not belong to the Imperial Guard regiments that they are fielded with. Instead, they are trained in the Scholae Progenia of the Imperium, institutions that train orphaned children to perform specialised roles.
Outside of the tabletop games, Stormtroops make an appearance as third-tier troops for the Imperial Guard faction in the video game Warhammer 40,000: Dawn of War: Winter Assault. Since the game's Imperial Guard faction is based on the Cadian regiment, the Stormtroopers are also referred to as Kasrkin.
In White Dwarf US issue #302/UK issue #303, an official article was published featuring Doctrines to allow Imperial Guard armies to take units of other types of Abhumans. The article featured Beastmen (Homo Sapiens Variatus, not quite as extreme as the original beastmen), Mutant Slave Levies (ordinary mutant slaves assumedly rounded up for cannon fodder), Feral Ogryns (more fearsome and more primitive than regular Ogryns), Nightsiders (originating from worlds of perpetual or near-perpetual darkness, little to no ability to see but perfect warriors for Night Fighting missions), Afriel Strain Soldiers (genetically engineered from DNA taken from great heroes of the Imperium, who were better soldiers but were very unlucky and unpopular), Subs (relatively genetically stable but still hideously deformed mutant sub-breeds) and Gland Warriors (Imperial Guardsmen implanted with special organs and glands that secrete combat-useful chemicals, such as stimulants and pain-killers).
Secondly, the Imperial Guard have a large range of tanks and armoured vehicles compared to many other armies, and have been heavily supplemented by the Forge World Imperial Armour series of books and resin kits. This appeals to the "treadheads" (or "tank-lovers") among the player community, and was catered to in the third and fourth editions of the game by the release of rules for an Armoured Company composed entirely of tanks. This army list can also be used to field Siege Regiments comprising of forward Artillery vehicles. It was Chapter Approved for the 2006 Tournament circuit. This was further developed upon in the Apocalypse Supplement with the Emperor's Fist Tank Company.
Another draw for players is the variety of model styles for the miniatures. The various Imperial Guard regiments produced or described by Games Workshop draw on a variety of historical and fictional inspirations. In the earliest editions, the Imperial Guard were very homogeneous in appearance and there was no visual distinction between regiments other than colour and decoration of their uniforms. As of the 5th Edition, however, there are several different stylings of infantry soldiers, in plastic, metal, or resin, available from Games Workshop or Forge World.
The 5th Edition of the Warhammer 40,000 rules has given the Imperial Guard considerable advantages. Firstly cover saves (saves conferred by terrain that allow models with weak armour to take saves) have been considerably improved. This combined with the "go to ground" rule means even a lowly guardsman who has gone to ground behind a stone wall can receive the same armour save as a space marine.
Imperial Guard tanks have received a double-edged sword type of improvement however. The new rules regarding firing ordinance mean that when ordnance hits its twice as deadly however the odds of Imperial Guard tanks hitting is low due to low ballistic skill. However tanks have become a lot harder to destroy as now glancing hits from anything other than an AP 1 weapon will mean that it is impossible to destroy a tank on the first glancing hit.
A tank regiment consists of between three and ten companies. A company consists of an HQ tank or squadron and between three to five squadrons of three vehicles.
The diversity of Imperial Guard regiments mean that there are literally thousands of variations on officers' ranks throughout the Imperium. However, local variations are generally tied to a basic standard list of officer ranks, for determining comparative seniority between regiments, a tentative hierarchy of which might be as follows:
Two other notable officer ranks exist amongst the Imperial Guard. Commissars (modelled on the Soviet political officers of the same name) are individuals attached to Imperial Guard regiments for the purposes of maintaining rigid Imperial discipline throughout the Guard. For command and control purposes, Commissars are not part of the regular command structure, and are usually subservient to the tactical decisions of line officers, though they possess wide powers to commandeer or assume command of other Imperial forces should the need arise. Exceptionally experienced commissars may be given field commands, such as Viktor Hark and Ibram Gaunt from Dan Abnett's series, Gaunt's Ghosts. The fact that any commissar can detain or execute any standard rank up to Lord General Militant (although summary executions are rare for ranks higher than Colonel) makes this distinction somewhat academic, as any commissar could remove an officer from command and assume control of the officer's unit.
The rank of Warmaster is a title issued by the High Lords of Terra to a military commander (usually a previous holder of the Lord General or Lord Marshal rank, or else an Admiral of the Imperial Navy) when one overarching leader is deemed necessary to command a crusade of historic magnitude (examples include the Warmasters Horus, Slaydo, Macaroth, Solon and Lord Commander Solar Macharius). A Warmaster’s military authority is absolute within his assigned area of operations, and it is for this reason that a Guard officer desiring this rank must be seconded by two Admirals of the Imperial Navy (similarly, a Naval officer holding the rank must be seconded by two Generals, or other senior staff officers, of the Imperial Guard). There is seldom more than one of these individuals in the entire Imperium at any one time. While it is said that a commander with the rank Lord Solar is higher than a Warmaster they are actually the same rank. On occasion the rank Warmaster, due to its association with Horus, simply falls out of favour and is replaced with Lord Solar.
Other ranks of import to the Imperial Guard are the Imperial Commanders, who have authority over the standing forces on an Imperial world (generally held by the Planetary Governor of the world in question) and the Lord Commanders of the Segmentae Majoris, a primarily administrative rank whose incumbents are responsible for overseeing and directing the Imperial military within one of the five Segmentae of the galaxy.
All remaining troopers are enlisted soldiers. Like the commissioned ranks, the enlisted rank structure can vary wildly from regiment to regiment. However, the Imperial Guard enlisted rank structure roughly equates as;
Others mentioned include Master Sniper (usually a Sergeant however due to his specialty, does not wear any insignia), Sergeant Major (confusingly, this is not an actual rank and instead is the name given to Warrant Officers) and Command Sergeant. Again, other variations exist based on planet of origin, Crusade or Army group etc. Some Sergeants in the Imperial Guard are known as 'Veteran Sergeants' but this is not generally an actual rank - Veteran Sergeants are either very experienced holders of the Sergeant rank or senior NCOs. The evolved Ogryns and Ratlings seem either to follow no ranking system at all or some internal ranking system, although they are obliged to obey Imperial Guard officers. Some Ogryns are given surgery to augment their intelligence, a process known as "Biochemical Ogryn Neural Enhancement" (BONE). Ogryns that receive these modifications are able to act as middlemen between humans and other Ogryns, and are often known as "Bone 'eads".
From the PC game, Warhammer 40,000: Dawn of War
From the Warhammer 40,000: Dawn of War: Winter Assault expansion pack.
From the Warhammer 40,000: Dawn of War: Dark Crusade expansion pack.
From the Warhammer 40,000: Dawn of War: Soulstorm expansion pack.
The portrayal of the Imperial Guard in novels has often been contradictory and varied. Some works portray them as competent modern soldiers capable of following combined arms tactics, while others show them as barely trained conscripts using ancient World War I-era tactics. This can be explained as a being the result of the incredible variety of the worlds which Guardsmen come from.
The Imperial Guard make several appearances in many of the video games that occur in the Warhammer 40,000 universe.