Astra Militarum - Regimental Organisation: From the greatest crusading armada to the smallest watch-tower garrison, Imperial Guard armies are composed of a mixture of distinct regiments. These basic units of organisation have not changed since the aftermath of the Horus Heresy. Each regiment is raised from a single world, its personnel bringing with them their native dialects, uniforms, customs and loyalties. However, any indigenous military structure is exchanged for the Munitorum-enforced standard. Internal politics, grudges or debts are -- for the most part -- ignored and allowed to fester so long as the morale and performance of the regiment is not affected. That said, the regiment's attached Commissars will gun down without compunction any who put their own personal vendettas before the wider cause of the Imperium's wars.Each Militarum Regimentum comprises multiple regiments, all of which come from the same planet. Because of the shared culture and fighting styles of regiments sourced from a single world, soldiers, officers and even officials of the Departmento Munitorum often interchange the term "Militarum Regimentum" and "regiment," referring to all Guardsmen from Cadia as being from the "Cadian Regiment." On their homeworlds, the forces who serve to defend the planet may have been split into battalions, divisions, cohorts, militia groups, geno-corps and a host of other formation names and compositions, but in the Astra Militarum these are all different types of regiment.Although there are many different classes of Astra Militarum regiment, each one is largely uniform in its tactical composition. Infantry regiments, for example, are unlikely to contain much or any heavy artillery, whilst tank regiments contain little or no infantry. Success requires Astra Militarum regiments to work together. Whilst this interdependence may at first seem like an inherent weakness, it is a necessary precaution. Should a regiment rebel against the Emperor, the Traitors will not have access to the supporting units needed to prosecute a full-scale war. When the Ocanan 15th declared its allegiance to the Ruinous Powers of Chaos it had little in the way of either heavy armour or artillery support and was unable to compete against the "combined arms" forces of the Cadian 17th Armoured and Elysian 110th Drop-Troop Regiments sent to eliminate them.Regiments are typically raised with a strength of several thousand soldiers but the precise numbers can vary enormously. The Valhallan 18th "Tundra Wolves" consists of over one hundred and twenty thousand men whilst the Vostroyan 24th "Iron Bloods" Armoured comprised less than one and a half thousand tank crewmen. Regiments of Baneblades and Shadowswords, each an armoured behemoth capable of laying waste to a small army by itself, rarely consist of more than a dozen super-heavy tanks. The basic principle held by the Departmento Munitorum is that regardless of the number of men at arms or the exact composition of armoured vehicles, the overall fighting strength -- and hence combat effectiveness -- of one regiment is equivalent to any other. This is clearly a gross oversimplification but a necessary one when organising wars on a galactic scale.Some planets are able to raise a variety of regiments. Cadia or Armageddon, for example, are huge worlds embroiled in seemingly endless wars whose populace are given ample opportunity to train in various aspects of warfare. By comparison, other worlds take great and often justifiable pride in their reputation for training a specific kind of regiment to exceptional standards. The pale-skinned, dark-eyed stealth infantry of the Night World Prometheron or the clockwork discipline of the Kalatian artillery brigades are excellent examples of this. Feral or Feudal Worlds, on the other hand, often provide only infantry or Rough Rider regiments, thus circumventing a huge potential culture shock.Leadership at company and regimental level is a duty assigned to officers recruited from the same world, and normally from the same founding, as the regiment they lead. This practice ensures that local planetary nobles are placed in charge of those culturally disposed to offer them deference; officers stay with the troopers they have spent solar months or Terran years training, and disruption to regimental morale is minimised. These officers will be supported and observed by regimental Commissars, attached during their founding by the Munitorum. These men and women must look to their regiment's morale and loyalty above all else, and will take any measure -- no matter how extreme -- to ensure the troops do not disgrace themselves, whether on or off the field of battle.Astra Militarum regiments are divided into several companies according to a complex set of templates detailed in the Tactica Imperium, each placed under the command of a senior officer. The number of companies in a regiment depends upon the type and size of the forces at the commander's disposal, but may consist of as few as three or as many as twenty. Companies are themselves organised into several platoons, typically between three and six. Platoons are typically comprised of a Platoon Command Squad and several ten-man Infantry Squads -- the most numerous of the Imperial Guard's forces.Support units, such as heavy weapons platoons and much-valued specialist units, such as battle tanks, artillery, Rough Riders and Abhuman squads, may be attached to a company for a single battle or the entire duration of a campaign. These are rarely permanent additions and are attached as needed by the regimental commanders. It is a common practice, especially amongst armoured and artillery regiments, to break down several companies and second them to infantry forces, granting heavy firepower to the platoons whilst providing troop support for the vehicles. If serving together for extended durations, attached units tend to adopt their foster-regiment's uniform and unit markings. This not only helps to avoid friendly-fire incidents, but also aids in promoting comradeship with the soldiers they will be fighting and dying alongside.