 Ever the Imperium's most disciplined of warriors, the organizational structure of the 13th Legion was a thing of beauty to appreciators of military organization. A peerless machine of uncompromising efficiency, these estartes were the epitome of a model army, the creation of a superlative tactical mind, and a product of the human realm that was Ultramar. As well as the uncompromising regime that their Primarch maintained there. Know then that this is a record of the tactics and operational dogma of the 13th Legion Ultramarines during the pre-heresy period and immediate aftermath of the drop-side massacre. From their inception, the 13th Legion were quintessentialists of the strictures laid down by that famous work of Terran military organization, the Principia Bellicosa. Standardizing themselves along the patterns prescribed therein, the Legion made little to no effort in revising it, seeing it as an exceptionally rational system of logistical administration in little need of reform. This was not exactly uncommon within the Legion as a starty, as one's acolytes will no doubt recall from similar records in the past, the early legions were all modeled upon the precepts of the Principia, newborn and shorn of the characters they would later come to possess. The 13th, however, was notable in just how little battlefield experience led them to modify the tenants of the great work. If anything, their commitment to its structures only became more resolute the more campaigns they engaged in. Companies were formed of roughly a thousand warriors, give or take situational combat losses, and from there ten companies composed the chapters of the Legion. Decimalization was a system later favored by the Primarch himself, who simply expanded the Principia's remit when enacting what few reforms he made upon assuming command of the Legion. It is owing to the retention of early crusade-era structures and indeed the Legion's eventual size that it counted amongst its number more chapters than any of its fellows, at over 250. The Legion was one to ever favor tactical flexibility. As such, it possessed few specialized companies in the manner their cousins did. A starty's who, by experience or talent, were adept in one form of warfare or another, were spread as evenly as possible throughout the Legion. It was an expectation placed upon each ultramarine company that it could defeat any foe that they faced with minimal losses. As a common 13th Legion aphorism went, to take a town, send a legionary. To take a city, send a squad. To take a world, send a company. To take a culture, send a chapter. While this is not strictly speaking Legion dogma, the truth it contained nevertheless formed a core around which the Ultramarines organized and comported themselves. In this, they were augmented by Gilliman's tactical and logistical support, which ensured that the Legion's specialized companies were well equipped with whatever non-standard weaponry, equipment, or ammunition they needed to operate at peak efficiency. This extended beyond the company to the chapter level. Each Legion chapter was equipped with a perfectly balanced mix of tactical, assault, artillery, armor, and aerial forces. That a Legion which counted at its peak a quarter of a million a starty's could be maintained at such operational levels across the entire galaxy is a sterling testament to Gilliman's logistical genius. When or if required, the Ultramarines would work with locally sourced weaponry, armor, and vehicle variants into their doctrines, should part of their armory become difficult to maintain owing to operational exigencies, such as distance, supply chain issues, or anything similar. Owing to the demands of the Great Crusade, this would, for example, lead to one chapter possessing a markedly higher number of say, Volkite Beam weaponry than another, if such arms could be obtained with ease from a forge world in the local volume. These changes, should they be made, were expected to have little to no impact on tactical efficacy. Squads armed with such weapons were to use them in fulfillment of the precise tactical role they were defined in Under Legion Doctrine. Inevitably, and despite the best efforts of the Ultramarines, battlefield experience did lead to some deviations from the norm, as by some quirk of recruitment ground, campaign experience, or supply availability, or a combination of these and more, chapters found themselves forming specialized tactics against the express wishes of Legion Doctrine. The fourth chapter, for instance, colloquially known as the Aurorans, operated five times as many armored vehicles as their fellow chapters, while the 22nd or Nemesis chapter was one of the few Ultramarine formations to operate destroyer units for extermination operations. The Primarch made his distaste for destroyer squads known widely, seeing the employment of a radiation, chemical, and phosphax weaponry as uncivilized. But ever the pragmatist, he did not follow the path his brother Vulcan had, and outright banned their use. Gilliman's mind knew that depriving his warriors of such arms would harm the potential tactical efficiency, and potentially place his astartes at risk if their employment was necessary. Never mind that this required his public position to be opposed to their use, such hypocrisies were ever the Primarch's stock in trade. A cost benefit, shall we say, weighed by his personal acumen. In typical Ultramarine's fashion, especially affectatious formations developed in one theater or another in response to specific on-the-ground situations, eventually would find themselves folded into broader Legion doctrine, but only after scrupulous tactical reviews and reports had been compiled, researched, and debated at the highest levels. One such example were the Legion's Full Mentarii Terminator squads, formed shortly after the Primarch observed the Tyrant Siege Terminators of the 4th Legion Iron Warriors. Equipped with similar loadouts to the Tyrants, Full Mentarii Astartes were clad in Cataphractii Terminator armor plate, and equipped with the heaviest weapons portable upon those suits, typically Cyclone missile launchers or Reaper autocannons. Distinct from the Tyrants, however, was a suite of awe-specs arrays and targeting systems, designed to allow squads to operate with a peerless level of fire cohesion, bringing the devastating weapons to bear with terrifying accuracy. The creation of these squads was said to have been a point of distinct bitterness for the 4th Legion's Primarch Pertorabo, who is rumored to have stated to Gilliman in a missive that such behavior was precisely what distanced the Ultramarine's Primarch from so many of his brothers. The 500 worlds of Ultramar, serving as a base of operations far larger than any other Legion counted under their direct control, allowed the Ultramarines, in combination with their extensive supply chains, to maintain a higher than average number of all armored vehicle patterns available to the Legion as Astartes. In typical 13th Legion fashion, these numbers were sustained in a well-balanced spread of vehicle classes and roles, and while the Legion would never, even with its size, possess the armored core of the 4th Legion iron warriors or 10th Legion iron hands, they could always call upon the precisely required number of vehicles for any given operation. Should a mechanized push be called for, all chapters possessed enough Rhino-armored carriers to transport every Astartes capable of riding in those machines. Similarly, the requisite amount of land raider and Spartan main battle tanks were available to process doctrinally armored spearhead assaults, under rapid-moving covering fire supplied by Sikharan support tanks, or perhaps in the wake of a bombardment by Legion whirlwinds or basilisks. Where the Legion chapters would differ is in the expertise level. The aforementioned 4th chapter, the Aurorans, proved exceptional at prosecuting armored warfare with super-heavy Dlave and Falkion destroyer tanks. Where the 13th notably lagged behind others was in the numbers of Starships at their direct disposal. Never one to claim mastery over areas he admittedly knew little. The Primarch, known to favour close operational coordination with other Imperial forces, deferred to what he saw as the experience and calling of the Imperialis Armada, the Fleet Arm of the Exertus Imperialis Human Auxiliary. Gilliman routinely seconded himself to Navy wings, if heavy-capital ship actions were required for a space-based conflict, preferring instead to outfit the Legion's own ships for invasion operations, and if needed, near-avoid engagements. As such, the Legion could even at its height only count 30 to 35 heavy-capital ships under its direct control, the vast majority of which had been with the 13th since they had left Terra at the beginning of the Great Crusade. Even of these, many had been heavily repaired and retrofitted over these two centuries, notably in the aftermath of the pre-Reunion conflict in the Osiron cluster. While the Legion did, by the outbreak of the heresy, possess two Gloriana-class battleships, including the McCraggs Honor, the 26-kilometre-long behemoth that sat amongst the largest of her class, the bulk of its fleet were cruisers, and battle barges of medium tonnage, as well as a large number of purpose-built strike cruisers, outfitted for speed and carrying capacity. The preference for these latter ships allowed the Legion its desired range of deployment and flexibility in operations, but would see them vastly outclassed by other Legion fleets, notably the capital ship-heavy 7th Legion Imperial Fists, 14th Legion Death Guard, and, to disastrous ends, 17th Legion word-bearers. Command structure was, as with all things, concerning the Ultramarines, rigid and hierarchical. Naturally, Gilliman held Supreme Overall Command, delegating the use and direction of all Legion assets, as well as enacting direct command over any theater he himself was present in. Below him were the 250 chapter masters, each responsible for 10,000 Astartes, as well as their attached fleet elements. Every 1,000 Astartes was led by a company captain, and below them served the attendant sergeants and lower officers. A company captain who distinguished himself would often be elevated to the ranks of Legatii, senior officers who served directly under the chapter master in a support command role, operating outside the formal command structure with the Tetrox and their own Legatii, who assumed command of both military and civilian government in the various spheres of Ultramar. The Tetrox were responsible for these spheres' defense, and every aspect of its manufacturing and supply efforts pertaining to the Legion. The four Tetrox were mighty champions of the Ultramarines. Their elevation to the office deemed a supreme honor amongst their fellows. They were guarded by the Legion's elite warrior Khadra, the Suzerain in Victoriai squads, veterans who would take to the battlefield clad in Artifacer crafted power armor and bearing arms as the warriors of old did, a power axe and a boarding shield. However, these elites were not simply elevated to their positions on martial merit alone. The Thirteenth did not put stock in mere skillet arms, as some of their fellow legions did, so an Invictarius was expected to demonstrate an equally impressive aptitude for the skills of governance, organization, administration, judicial insight, and so on. The Invictarii were expected to aid the Tetrox in governing their respective spheres of control in Ultramar, and could themselves be expected to one day rise to the ranks of Legatus or even further. Squads of Suzerain's raid for warfare could also be found seconded to Legion chapters when their skills at war-making were most needed, or when the Invictarii themselves requested frontline duty to gain further battlefield or command experience in the ever-fluxuating frontlines of the Great Crusade. Lastly, one final organization, ill-understood but known to have existed, conducted its affairs in the shadows of the Legion's most prominent members. The Vigil Operatiii, founded by Gilliman himself as he crafted the structure of his domain, was a clandestine arm of Ultramar's authoritarian regime, operating to silence internal threats deemed too dangerous to simply be processed by the just cause of the Primarch's iron-clad legal system. The Operatiii were in effect a secret police, and coordinated heavily with both the Legion and Exertus' intelligence operations, bending their considerable talents to the uncovering of and silencing of dissent and ideological impurity that may have sought to question Gilliman's regime. Additionally, and more publicly, they coordinated recruitment, training and deployment of human auxiliary regiments and planetary defense militias, although naturally deferring to Legion command should the latter acquire the use of these forces. The Vigil Operatiii were however not baseline humans themselves, rather augmented individuals who had, owing to a late discovery of some genetic defect or discrepancy, been unable to complete their Astartii's implantation and conditioning procedures. Disbarred from Legion membership but not active service, their employment in this manner was something that typified the type of man Gilliman was. Why should qualified and highly trained men simply be discarded when their skills could be utilized for the good of the regime? Other legions, by nature or recruitment policy, tended to either abandon washout recruits into military prisons or the general population, or in most cases, kill them to protect gene-seed codes. Gilliman was perhaps understandably of a different vein, and doubtless the presence of Ultramar as a military regime allowed such men to find a place more readily. No other Legion operated the same stellar government that the 13th did. Regardless of however tangentially related to Legion command they were, the Operatiii were a supremely useful arm of Ultramarian internal affairs, especially during the dark days of the Shadow Crusade and the spread of cultist operations conducted by Lorgar and his word-bearers. Even more direct Legion recruitment was undertaken by a specialized formation within the 13th known as the Evocatiii. Originally introduced by the Legion's first master, Gren Vesotho, it was later reorganized and renamed into its modern incarnation. Composed of two double strength chapters, the Evocatiii ranks were filled with Legion neophytes at various stages of their Astartes conditioning and implantation processes, while Legion veterans rotated out of regular duties, forming what passed for a dual officer and teacher corps. The late commander Vesotho was fond of flooding these neophytes on the front lines of 13th Legion campaigns. Gilliman's approach was far more restrained, assigning them to defensive positions on border planets in Ultramar's volume, where they could operate both as a primary line of defense and undergo a strict regime of training exercises and memetic habituation. Depredations of Orc raiders and other Xenos incursions meant these neophytes were rarely a need of opportunities for combat experience, but were never overwhelmed to the same degree that they would have been under Vesotho's command. That is, of course, until the events of the Shadow Crusade. In the strategic sphere, the Ultramarines were renowned for their inbuilt tactical flexibility, extending from the squad level to the chapter and indeed Legion command. This tractability was rooted in the Legion's paramount maxim of the interplay between the practical and theoretical, a creed developed by the Primarch himself. Already psychologically inclined towards its practice, Gilliman elevated it to doctrinal levels. Under its strictures, the Ultramarine is expected to consistently apply the tenets of logic, analysis, and reason in his best efforts to eliminate the deficiencies within any military situation. This could apply, again, on the level of a squad engaging a Xenos mob on the desert of an unknown world, or to the chapter captain's planning theater-wide stratagems. The courage, skillet arms, and self-control of Anastartes was present in the practical, while in the theoretical lay his planning, scrutiny, and judgment. A common exercise amongst Ultramarines in downtime between engagements was to debate hypothetical scenarios with each other, applying the rigors of practical and theoretical to better understand both themselves and those they served alongside. While such strategic deliberations are of course not unique to the Thirteenth Legion, and the spirit of animated discussion regarding the arts of war was alive and well in other legions, the Ultramarines were unique in how their philosophy was deliberately fashioned to improve not only the individual's tactical knowledge, but that of the Legion as a whole. As the sands of Istvan V were being soaked with the blood of betrayed legions, the Ultramarines represented a staggering 250,000 legionaries present in the Imperium itself. Primarily they were spread over expeditionary fleets in the Galactic South and East. Of this number, Gilliman recalled 20 whole chapters, four-fifths of the Legion's strength, to a muster at Calth, ostensibly on the orders of Warmaster Horus. There, the Legion was expected to move onward and commit the bulk of its forces to the prosecution of the Greenskin Empire of the Warlord Gashlach, alongside the recently swelled 17th Legion word-bearers. That there in the closing days of the Great Crusade existed a foe that required the almost total commitment of two of the largest Astartes legions was patently absurd, but it was understood that in the higher echelons of the Imperium there existed a diplomatic effort by Horus to forge a bond between the Primarchs, Lorgar and Gilliman, neither of whom countered the other in high esteem or friendship. Gilliman, ever the trustful and obedient brother, welcomed Lorgar with open arms. It was a mistake for the ages, and shall no doubt be committed to a record very soon. Ave Imperator Gloria in Excelsis Terra Please like, subscribe, comment, let me know your feedback, and as ever, thank you very much for watching.