Imperial Army

The Imperial Army, known formally as the Imperialis Auxilia and the Excertus Imperialis respectively (the hosts of the Imperial Army and its auxiliaries) was the Imperial military force comprised of normal men and women that served as the ancestor of the modern Imperial Guard of the late 41st Millennium. Unlike the Imperial Guard, the Imperial Army contained ground, air and space assets all within the same table of organisation and there was no differentiation between space-based and ground-based branches of the service. The origins of the Imperial Guard date back to the time of the Great Crusade in the late 30th Millennium when the Emperor of Mankind conquered a large swathe of the galaxy and forged the Imperium of Man. As the Great Crusade progressed and more worlds needed to be liberated, the Imperium's need for more troops increased dramatically. Even the mighty superhuman armies of the Legiones Astartes could not alone complete the task at hand.

It was therefore decreed that each of the liberated worlds would supply men-at-arms to bolster the war effort. Although not as powerful as the Space Marine Legions under the various Primarchs' command, the Imperial Army regiments were nevertheless useful additions to the Astartes' fighting strength. Unlike in the present-day Imperium, where the Imperial Guard serves as Mankind's front-line armed force in the defence of the Emperor's realm, the Imperial Army was never anything more than a reserve force for the Imperium during the Great Crusade, and its troops were usually tasked with garrison duty or mopping-up operations. Only in the last decades of that great campaign did Imperial Army troops finally fight directly alongside the forces of one of the ancient Space Marine Legions on campaign.

In the aftermath of the Horus Heresy in the early 31st Millennium, a great reform of the Imperium's bureaucratic and military structure was undertaken at the behest of the Primarch Roboute Guilliman. To prevent the possibility of a large-scale interstellar rebellion from consuming the human-settled galaxy again, the titanic armies of the Imperium were divided into three basic parts: the Space Marine Chapters of the Adeptus Astartes, a ground-based force of mortal soldiers that would replace the fractured Space Marine Legions as the Imperium's front-line troops and a space-based service containing all of the Imperium's naval assets that was responsible for all space-related transport and combat duties. This reform led to the formation of the modern Imperial Guard and Imperial Navy.

Wars of Unification
During the turbulent era known as the Age of Strife, the Sol System and the nearby star systems that had been colonised by humanity during the Dark Age of Technology were effectively cut off from interstellar travel or communication with each other due to the massive Warp Storms that swept the galaxy. Little remained of the once sophisticated civilisation of Old Earth's glorious past as the center of a growing human interstellar civilisation marked by advanced science, high culture and wondrous technologies. Techno-barbarian warlords and their warrior hordes continuously fought over the planet, which had become little more than a massive battleground for their wars of attrition. They made use of chemical, biological and even thermonuclear weapons of mass destruction, and slowly transformed the cradle of Mankind into a battered, post-apocalyptic wasteland across most of its scarred surface.

It was against this backdrop of oppression, violence and casual brutality that the Emperor of Mankind first revealed Himself to the people of Terra. In secret, He had been planning for this moment in history for millennia, ever since the Age of Strife had fractured what remained of the ancient human federation which had once stretched across a part of the galaxy. The Emperor moved to create the military organisations he would need to begin the reunification of Mankind, and He used the raw materials at hand after millennia of savage conflict between the techno-barbarian nation-states of Old Earth. Formed during the savage continental wars that had engulfed Terra in the Age of Strife, the genetically-enhanced warriors known as Genos comprised the first units of the force that would become the Imperial Army and would serve as the prototypes for the later development of the proto-Space Marines called the Thunder Warriors. Among the most well-known of the regiments composed of Genos were the so-called Strife Epoch regiments raised by the Emperor to initiate the Unification Wars intended to reunite all the warring peoples of Terra beneath His benevolent rule. The genetically-enhanced Strife Epoch regiments came to form the nucleus of the armed forces that would later support the even more genetically advanced Space Marine Legions during their reconquest of the human-settled galaxy. The Emperor began His conquest of Terra with the intent to reunite the warring techno-barbarian nations into a unified planetary government and then use Terra as the springboard from which to begin his reconquest of the galaxy under the aegis of an Imperium of Man dedicated to the Imperial Truth of progress and reason.

The Old Hundred
The Genos proved throughout the conflict to reunite Terra that became known as the Unification Wars to be a most effective and adaptable military force. During this time, the Genos practised gene mustering, an essential tool during those caustic years of atomic hurricanes and drifting rad clouds. Through the use of genetic manipulation, the Genos were able to develop tough and physically imposing warriors, but they complemented their brute strength and resilience  by importing smart, proven field commanders from other forces that kept their genetic pool pure. The genetically-enhanced regiments of this period such as the lauded Geno Five-Two Chiliad would go on to become amongst some of the oldest brigades to serve in the later Imperial Army. Each Geno of the Imperial Army, in addition to referring to the individual geneticaly-enhanced soldiers also was a term applied to an elite force of the Imperial Army that was composed of one thousand companies, with each maintaining a proud martial tradition. These surviving Genos were proud members of the "Old Hundred," the Strife Epoch regiments that the Emperor, in His grace, had maintained in existence after the completion of the Unification, provided that they had pledged their loyalty to Him. Many thousands of other Geno units had been forced to disband after the achievement of Unity, or had been actively purged and chemically neutered, depending on their level of resistance to the new order brought by the unification of Terra under the Emperor's new planetary government.

Hammer of the Emperor
When the great Warp Storms that had cut off Terra since the end of the Dark Age of Technology subsided, and the Age of Strife came to an end in the late 30th Millennium, the Emperor of Mankind deemed it time to begin His Great Crusade. This was a massive campaign begun in ca. 800.M30 to conquer the galaxy by which He and His armies would free all human-settled colony worlds from alien oppression or primitive ignorance and reunite the human race across the galaxy under the single banner of the new Imperium of Man. The Great Crusade marked a brief era in human history of rebuilding, reunification and rapid technological advancement following the complete regression of Mankind into techno-barbarism during the 5,000 Terran years of the Age of Strife. The Emperor sought to unite all of humanity under one banner following the Long Night of the Age of Strife, and end inter-human conflict. Once united, the Emperor intended to begin the next stage of His great plan to ensure human domination of the Milky Way Galaxy.

At the forefront of this time of expansion and reclamation were the mighty Space Marine Legions -- the Legiones Astartes -- the finest warriors humanity had ever created, each the equal of a dozen normal men. Despite their formidable battle prowess, the forces of the Space Marines were not limitless, and the relentless demands of building a galactic empire pushed the Legions further apart. Separated by countless thousands of light years, their presence became ever more scattered and diluted. No doubt from the very beginning, the Emperor realised that while his Legiones Astartes would be his foremost agency of war and conquest, the sheer scope of the undertaking of the Great Crusade -- no less than the liberation of the entire galaxy would require far more manpower, spread over a wider area, than even hundreds of thousands of Space Marines could hope to achieve, simply because they could not be everywhere at once, nor would they be best served by undertaking roles ably filled by ordinary humanity. From this reality the Excertus Imperialis was born; billions of second line and support troops, functionaries, labourers, void crew, logisticians, almoners, adepts and staff officers, and the countless quantities of weapons, equipment and war machines, void conveyances and warships they needed; all to make the Great Crusade a reality. Within this vast body of men and women under arms, organised and formulated by the Emperor's own transhuman intelligence, were many highly specialised divisions, each created to serve a singular purpose, each a vital cog in the vast Imperial war machine.

The Emperor required more manpower to ensure the momentum of the Great Crusade did not falter. Each newly conquered or liberated world brought into Imperial Compliance during the course of the Imperial campaign was assessed and a census taken of its population. From this, the Emperor's administrators of the Corps Logisticae, the forerunner of the later Departmento Munitorum, calculated the tithe that each world was to pay in the form of regiments of soldiers and war materiel. The numbers of regiments raised from each world varied enormously in accordance with the size of each individual planet's population. Sparsely populated worlds would be tithed to supply only a handful of regiments annually, whilst the overcrowded Hive Worlds near to the Galactic Core would have to supply hundreds of regiments every standard year. This huge body of soldiers soon became known as the Imperialis Auxilia, or more commonly referred to as the "Imperial Army".

Although the Imperial Army was not as powerful as the Space Marine Legions under the Primarchs' command, the Imperial Army regiments were nevertheless useful additions to a Primarch's fighting strength. A Space Marine Legion often had hundreds of auxiliary Imperial Army regiments fighting under its command. These troops were used to reinforce the Space Marines and were frequently deployed in sieges, mass invasions and to garrison newly conquered worlds. The Imperial Army was rarely deployed within the home system of the regiments that comprised it. In fact, this was actively avoided by the Primarchs in command of these regiments to ensure that the soldiers' loyalties lay first and foremost with the individual Primarch and the Space Marine Legion to which they had been attached, and alongside which they fought.

Numberless Ranks of the Excertus Imperialis
The Excerrus Imperialis of the Great Crusade era was a vast organisation whose numbers in a literal sense are uncounted; no accurate measure of it has ever been possible, so numerous is it, widespread across the stars and in flux as units are disbanded or suffer attrition, and fresh units, recruits and indentures are added to its ranks. As a structure, it is almost unfathomably complex. It formed the incomprehensibly vast support structure of the Great Crusade, including in its sweep the Expeditionary fleets' front line auxiliary and second line reserve forces (known collectively under the sub-title of the Imperialis Auxilia -- or Imperial Army informally) and the billions of planetary militia-raised provincial defence. It also included the myriad support organisations, colossal labour hosts, penitentiary legions, the warships and crew of the Imperialis Armada, the vast Æxactory, Notary and Tithe corps, and nominally the Remembrancers, the Iterators and the enforcers of the Imperial Truth -- all were bound by its writ. Although notionally it was to the Officio Militaris on Terra and via them the Imperial Court to whom the numberless ranks of the Excertus Imperialis answered, it was always in truth subordinate to the principal agents and independent powers of the Great Crusade who commanded it on a daily basis: the Legiones Astartes and their Primarchs, the Mechanicum and their Titan Legions, the Knight Houses, the Rogue Traders Militant, the Imperial Commanders who governed the Imperium's worlds, the Navis Nobilite and the Collegia Psykana, all had better and more immediate call on the Excertus Imperialis to obey. So it was when the Imperium was riven by the Horus Heresy, so also was the Excertus Imperialis; turning traitor or remaining loyal with long accustomed masters to lead them, while even its more independent arms were forced abruptly to choose sides in a war not of their making. As the Great Crusade died, so did the organisation that served it, supplied it and fed its growth come to an end, split by division and torn in blood.

The Horus Heresy
During the Great Crusade, it was common practice to subordinate Imperial Army regiments to the Imperial Expeditionary Fleets controlled by the Space Marine Legions. But after the corruption by the Chaos Gods of the Emperor's most favoured son and Imperial Warmaster, the Primarch Horus and the onset of the Horus Heresy in the early 31st Millennium, it soon became apparent what a monumental mistake it had been to place Imperial Army units under the control of the Space Marines Legions. During that time of civil war, the Imperium was split asunder and humanity turned in upon itself in a bloody war which almost saw its complete destruction. The Warmaster led fully half of the legendary Space Marine Legions in open revolt against the Imperium which had created them and the master which they were sworn to protect. Alongside these legions of genetically engineered warriors marched millions of Imperial soldiers, men and women drawn from across the colonies of Mankind and gathered under the banner of the Emperor. When Horus turned against his father, he took countless soldiers and ships of the Imperial Army with him. Those men which had once fought for humanity during the Emperor's Great Crusade to reunited the human-settled galaxy under the Imperial banner were instead pitted against each other in a bloody struggle as the Heresy unfolded and civil war spanned the galaxy.

Among the Traitor Legions, almost all of their attached Imperial Army formations uniformly followed their masters into rebellion, out of fear or blind faith. Even amongst the Loyalists, Imperial Army units with an officer cadre of genetically-enhanced Geno warriors performed poorly, usually driven to destruction by the inability of the unaugmented human soldiers to keep up with the demands of their transhuman Space Marine leaders. Over the course of the Heresy, entire armies of mortals were raised and squandered both by the Traitors and the desperate Loyalist commanders. Across the breadth and width of the galaxy, the Imperial Army tore itself apart in monumental battles, on a scale unseen in human history. Combined forces of fleet and army elements moved from world to world at the command of Generals and Lord Commanders whose loyalties were unknown to both sides. Thousands of pocket empires were carved out by ambitious commanders with no true loyalty to either side. Over the course of the following centuries, and at a cost of billions of lives, the Imperium was slowly reforged, forever tainted by the blood spilt in the massive civil war which had almost destroyed it.

From the Ashes
"Peace? There cannot be peace in these times."

- Lord Solar Macharius

After Horus was defeated and his armies had taken flight from Terra into the Eye of Terror, the Imperium was in chaos, weakened and shattered after long years of war. Even though the need for the Imperial Army was as great as ever, those Loyalist leaders that remained, led by the Ultramarines Legion's Primarch Roboute Guilliman, were fearful of a repeat of the rebellion which had cost them so dearly. In the aftermath of the Horus Heresy, massive changes were implemented to civil and military administration of the Imperium on Guilliman's orders, a period forever after known as the Imperial Reformation. To prevent the possibility of large-scale rebellion occurring again, the titanic armies of the Imperial forces were divided. The Space Marine Legions were dissolved and split into separate, 1,000 Astartes-strong Chapters. No longer would the superhuman Space Marines serve as the Imperium's frontline military force. That task would fall to the mortals who had once comprised the Imperial Army -- there were far more of them than there were of the surviving Loyalist Space Marines, and more importantly, should they turn Renegade, the damage they could do was far less. The newborn Adeptus Astartes would assume the role of planetary assault forces and elite special operations troops.

Thus the  Imperial Army as it had been for centuries ceased to exist. The link between the Imperial Fleet and Army was formally and bureaucratically severed -- never again would Imperial ground commanders be given direct control over interstellar ships or even their own units' air support. From the ashes of the Imperial Army were born the separate armed services of the Imperial Navy and the Imperial Guard. The Imperial Guard was reorganised into smaller units known as regiments, an existing formation from the old organisation structure of the Imperial Army, and centrally-trained political officers known as Commissars were universally introduced to watch out for disloyalty and to keep the Guardsmen and naval crews properly motivated in defence of the Imperium. The inter-dependence of the newly formed Imperial Guard, the most numerous of the Emperor's troops, ensured that should a regiment turn against their oaths of fealty, they would not be able to spread their treachery beyond a single world, and should an Imperial Navy fleet mutiny, they would not have the ability to resupply or deploy ground troops. The Imperium had learned a harsh and painful lesson following the dark days of the Horus Heresy.

This was the birth of the Imperial Guard as it exists in the late 41st Millennium. Divided by logistics and separated by the gulfs of space and myriad different planetary cultures, it remains united by a common duty to the God-Emperor and Mankind. Riddled with inefficiency and bureaucracy, it is often slow to respond and resistant to change, but it continues to function despite the rules laid down by the Adeptus Administratum to limit its power and use by untrustworthy commanders. That no one man can know the extent of the Imperial Guard's total strength at any time is part of this protection and part of its power, as in this way it is truly an army of unlimited size and resources which can meet the demands of interstellar warfare but which will only ever answer to the will of the God-Emperor Himself.

Imperial Expeditionary Fleet
The Expeditionary Fleet was the basic military unit of the Great Crusade. According to the Imperium's ancient War Council logs, at its peak in the early 31st Millennium, some 203 standard years after it began in ca. 800.M30, there were 4,287 primary Expedition Fleets engaged upon the business of enforcing Imperial Compliance and extending the Imperial aegis across the galaxy as well as 60,000+ secondary deployment groups involved in Compliance or occupation endeavours. A further 372 primary expeditions were in the midst of regroup and refitting actions, or resupplying as they awaited new tasking orders.

Imperial Expeditionary Fleet Rank Structure

 * Lord Commander - A Lord Commander was a senior position within the Imperial Army hierarchy, charged with commanding an entire Expeditionary Fleet, unless a Primarch was attached to it, who would take overall command of any Expedition where he was present. Under these circumstances, a Primarch took precedence as commander of the Expeditionary Fleet while the Lord Commander was relegated to being temporarily placed in charge of the only the elements of the Imperial Army assigned to the fleet.
 * Master of the Fleet - Subordinate to the Lord Commander or the senior Astartes officer in the Expeditionary Fleet, the next highest rank was the Master of the Fleet.
 * Captain - A Captain was the commanding officer of a given warship, regardless of class or tonnage, within an Imperial Expeditionary Fleet.
 * Executive Officer - The Executive Officer was the second-in-charge of an Imperial warship, and subordinate commander in the absence of a vessel's captain.
 * Shipmaster - The Shipmaster was generally the senior-most Warrant Officer and most experienced voidsman onboard a given starship. Often the Shipmaster was tasked with critical responsibilities, such as stellar navigation and the keeping of the starship's log. In addition, he or she might oversee the keeping of the ship's attitude jets, hangar decks, and stores and supplies.
 * First Master - Ship's officer.
 * Master - Ship's officer.

Imperial Army Regiments
The indentured troops of the Imperial Army were assimilated into the command structure of the Space Marine Legions, and fell under the direct authority of the Primarchs of each Imperial Expeditionary Fleet and his subordinate Space Marine officers. Space Marine transports would arrive at each world and carry the regiments of the Imperial Army raised there as part of the Imperial tithe away to fight on distant battlefields throughout the galaxy. During this bygone era, the Imperial Army and its subset formation, known as the Imperial Fleet, functioned as a single entity, with army commanders exercising overall command of both elements. The regimental formation and overall structure of the ground-based units of the Imperial Army was very similar to that of the present-day Imperial Guard.

Many sources from the Great Crusade era concur that the size and organisation of an Imperial Army regiment was dictated by what would fit into the interstellar ships available at the time. This meant that most Imperial Army regiments number approximately 3,000 troops who would be carried to their destinations by a single dedicated troop transport vessel or one of the many available classes of Imperial Cruiser. This approach ensured that an individual regiment was deployed with each warship in an Expeditionary Fleet. It was doubtless a brutal but necessary equation; the losses of ships in the Warp or through enemy action did not result in remnants of a given regiment being left scattered among other vessels, and no longer being combat capable.

Each regiment maintained its own infantry, armour and support troops, making it capable of both assaulting and defending varied terrain against most types of opposition. Imperial Army regimental commanders were free to train and equip their regiments as they wished, only being limited by the resources readily available. Keeping men from individual worlds together to form the natural bond of brothers-in-arms was also an important element in creating cohesive fighting formations. In many cases, men from different worlds could barely understand each other's languages, let alone the nuances of different social mores, customs, tactics or planetary-specific special equipment. Such difficulties in cross-cultural communication could all degrade a formation's efficiency in combat, so it became the rule in the Imperial Army that each regiment was composed of troops raised from the same world, and they all travelled together on the same transport or warship of the Imperial Fleet. All of these realities would eventually lay the groundwork for the tradition of the Imperial Guard that a regiment is always recruited from a single world and fights together as a whole unit whenever possible.

Combined Regiments
However, over the course of numerous campaigns, regiments were invariably whittled down by casualties, necessitating the re-combination of shattered formations into ad hoc groupings. References exist in the Codicium Arkathalor (a fragmentary record of the campaigns of the Pandora Sector in the late 30th Millennium) to "split" regimental formations. The codex makes it clear these were mixed formations made up of heavily mauled Imperial Army regiments re-combined to restore their status as effective fighting formations. Likewise, some specialised troops, such as xeno-cavalry or Ogryns, have apparently always been split between larger formations to bolster their efforts. Their specialised capabilities made them unwieldly to operate at the regimental scale, except in certain rare and often excessively emphasised campaigns.

The ancient traditions of splitting specialised regiments and recombining remnants are the subject of heated debate between Imperial commanders to this day. Many commanders declare that the reduced efficiency of combined regiments make them barely worth their rations; infighting and mistrust made the diverse elements function as less than the sum of their parts and mutinies in such mixed formations were commonplace. Others were interested only in the number of men-at-arms that could be fielded -- their successful integration as effective combat units was of less interest than their overall physical size. The Tactica Imperium presents both viewpoints as equally valid, indicating that no final resolution on the matter was reached, and that some commanders found both strategies useful depending on changing circumstances.

Battalions
The regiments of the Imperial Army were further broken down into battalions. A standard regiment consisted of three or more battalions plus a number of specialised units which were kept in reserve at the regimental level. These regimental support detachments could be attached to battalions as and when they were needed. The battalion was the smallest formation of the Imperial Army that could act as a combined force, and as such they sometimes operated independently from their regiment. Battalions were made up of two or more companies, plus a variable number of more specialised battalion support detachments.

Discipline Masters
The Imperial Army was used almost exclusively for garrison and pacification roles on both their home and foreign worlds throughout the early stages of the Great Crusade, but by the latter half they were fighting offensive battles and supplementing the Space Marine Legions as they began to be stretched more sparsely across the growing Imperium. The Imperial Army at this time was organised with no particular standardisation, and regimental makeups ranged from barbarians wielding Power Axes to advanced mechanised infantry armed with energy weapons whose designs have now been lost. During this time, the regiments were left almost exclusively to their own recognisance as long as they served faithfully, and conformed to the few restrictions placed on them.

Due to the sheer variety of worlds and subsequent Imperial Army regiments, a measure of standardisation was deemed necessary to allow the Army to function as a whole, although the sheer size of the expanding Imperium by this time prevented any true standardisation. The treatise that came to be known as the Tactica Imperium was penned and distributed, and a cadre of political officers were created to ensure proper and effective integration and co-operation between regiments. To instill discipline and loyalty in the regiments of the Imperial Army, regiments utilised these newly developed specialists known as Discipline Masters. These stern task masters were primarily responsible for maintaining discipline within the regiment to which they were assigned. They were also responsible for tracking down Imperial Army deserters that repudiated their oaths to the Emperor and shirked their soldierly responsibilities. Discipline Masters were known to use hunting eagles to help them track their prey. Their fanatical dedication to the service of the Emperor overrode any feelings of compassion, mercy or humanity when carrying out the summary executions of those found wanting, for which they employed a ceremonial Electro-scythe.

The Discipline Masters served as the ancestors and model for the later Commissariat and its merciless political officers known as Commissars. During this era, it was also common practise for Space Marine Primarchs to appoint certain Imperial Army officers to this special office. These veteran warriors ensured that the Imperial Army was unwavering in its duties to its Space Marine overlords. This would later prove disastrous, as those Imperial Army units subordinated to the command of the Space Marine Legions that turned Traitor uniformly followed their transhuman masters into rebellion, either out of blind fear or unfettered devotion. At the outset of the Horus Heresy, the first rebellious act of Traitor Imperial Army units was to kill their Discipline Masters, while in Loyalist regiments the Discipline Masters were forced to take extreme measures to maintain order, earning them their fell reputation for steadfastness and calculated brutality later passed on to their Commissar descendants.

Wargear
The sheer size of the Imperium, the unpredictable nature of Warp travel and the vast numbers of liberated worlds defeated any attempt to standardise the Imperial Army, and there was wide disparity in the wargear, drill and discipline of the various regiments. Each of the tithed worlds supplied troops to the Imperial Army as best they could. Those from developed Industrial Worlds were kitted out with sturdy Flak Armour and newly-minted, standard-issue Autoguns and Lasguns (the Autogun was the standard weapon for the Imperial Guard until the opening of the 32nd Millennium). Soldiers from primitive worlds were fortunate if they had a pair of boots and a gun. Some worlds supplied troops that were well-drilled and organised into squads, companies and regiments. Others supplied what amounted to little more than loosely ordered mobs or warbands. Despite this, the soldiers of the Imperial Army proved their value in hundreds of campaigns and across thousands of battlefields.

In the earliest days of the Great Crusade in the late 30th Millennium, the Imperial Expeditionary Fleets that set out from Terra only carried with them the means to fulfill a portion of their supply needs, and simply took what they needed from the worlds they conquered in their travels. Upon the completion of a successful Imperial Compliance action on a world, the Expeditionary Fleet would move on, leaving the assimilation of the planet into the Imperial fold to fleets of pioneers and Terran colonists. Each world, in time, would become fully capable of supporting itself and contributing to the needs of the growing number of Imperial Expeditionary Fleets. Such a state of affairs could not continue, for eventually each fleet would exhaust its supplies and be too far from a Compliant world capable of resupply. In these times, the resources necessary to fight a campaign were organised by the Lord Commander of each individual Expeditionary Fleet, a necessity of the times, but one that was wholly unsuited to the growing size and complexity of the Imperium. Oft times a Lord Commander fulfilled multiple roles; war leader, diplomat, exactor, mediator and logistician. Men who could fulfill all of these roles adequately and still have time for the strategic demands of a long campaign were few and far between and, as such, the newly formed Council of Terra recruited those whose minds could function in such a manner, empowering these administrators with the duty of maintaining the Emperor's armies in perpetuity as part of the Corps Logisticae. This was the earliest incarnation of the Departmento Munitorum.