Ultramarines - Legion Organisation: From its earliest incarnations, the XIII Legion had remained true to the strictures of the Principia Bellicosa, as laid down by the Emperor and His advisors at the beginning of the Great Crusade. The warriors of the Legion were organised into standardised companies of approximately a thousand warriors, then into chapters, each of ten companies.Unlike many of their brother Space Marine Legions, they made little attempt to re-codify the structure or vary the size of individual units. Instead, the War-born enshrined the basic strictures of this system as an honoured tradition of the Legion, one that was to see little modification even in its later years after the rediscovery of Roboute Guilliman, who expanded and elaborated on this structure, seeing in it great virtue, rather than replacing it.Roboute Guilliman also expanded on the XIII Legion's practice of observing how others fared in battle and adopting modified versions of their comrade Legions' tactics where efficacious. This spoke to Guilliman's own predilection for analysis and observation, and in this case what the primarch saw, he studied with a relentless precision, always seeking to distil and improve upon success and exceed the originator's accomplishments by the application of his intelligence and the diligence of his Legion. Such improvement was something he always believed a possibility, an attitude which at times brought the ire of some of Guilliman's peers.The operational doctrines of the XIII Legion favoured tactical diversity and the application of overwhelming force. As a reflection of this, the Legion maintained relatively few tactically specialised companies, instead choosing to spread those units which maintained large stocks of non-standard equipment and munitions evenly throughout the various companies of the Legion.It was intended that every Ultramarines company would be individually capable of meeting the enemies of Mankind on any terrain and in any theatre of war with equal ability and emerge victorious, magnifying this power in combination with the Legion's other chapters almost geometrically. To this end, each chapter featured a proportionate mix of tactical and assault units, armour and artillery as well as gunships and transports.With the sub-division of the massed ranks of the XIII Legion that occurred in the later years of the Great Crusade, reforming it into more individual crusade expeditionary fleets than any other single Legion, the value of the doctrine was quickly re-established and built upon. The Legion attempted to standardise much of its equipment base and supplement it where needed with local patterns, which if not the most potent or advanced of their type required lesser resources to mass-produce, in order to optimally meet the ever-expanding needs of its warriors. This factor itself would have great impact on the latter day development of Space Marine forces beyond the wars of the Horus Heresy.While this doctrine of structured adaptability was to become deeply ingrained within many of the Legion's chapters, there were some notable deviations from this pattern. Some few individual chapters, through long-held preferences or some quirk of supply, maintained notable strengths of non-standard equipment or personnel.The Ultramarines 4th and 22nd Chapters are the most noteworthy example of this, with the 4th, known within the Legion as the "Aurorans", operating roughly five times as many armoured vehicles as a standard chapter, while the 22nd, the so-called "Nemesis" chapter -- long a hold-out of the XIII Legion's Terran-born contingents -- maintained large numbers of Space Marines equipped as Destroyer units, and was one of the few Ultramarines formations to routinely be deployed especially to Exterminatus operations by the Legion.Roboute Guilliman was known to hold something of a distaste for such horrific weapons as fundamentally self-defeating; they destroyed the very ground on which they were used, which was to his doctrines a poor way to conquer or liberate a world. But this having been said, Guilliman held no outright ban upon such weapons of mass destruction's use in his Legion as Vulkan did, realising that in certain cases their use was all that would suffice, and strategically he would not let his Legion be without the ability to deploy phosphex, oxygen destroyers and even carbosilic cascades in extremes.Some few chapters retained and employed variations of the older XIII Legion's sub-structures and heraldry, marking achievements of the Terran first generation of the "War-born" or the disparate origins of their warriors, but these had faded somewhat over the standard years as the body of the Legion's demographic changed to favour the sons of Ultramar. By the closing solar decades of the Great Crusade all Ultramarines, regardless of origin, followed the same detailed organisational scheme, with only minor variations allowing for personal heraldry and honours among its highest echelons.All twenty-five chapters of the Legion -- a vast notional strength of around 250,000 Legionaries by the time of the Horus Heresy -- comprised then a single cohesive force with a fully integrated command forming together for grand strategic assaults or operating flawlessly in smaller detachments to carry out individual actions under this flexible arrangement.