 The great Crusade, and the baleful influence of their Primarch, had twisted the Resolute Fourth Legion into the bitter, resentful Iron Warriors. But this should not lessen the respect they may be accorded, however resentfully, for their undeniable skill in the role with which they found themselves. Masters of siege craft willing to bear any cost to grind the enemy into dust, the Legion found itself called upon to do the work others would not. To claim worlds no one cared to, to do the bidding of the Imperium without question. In doing so, they developed one of the most finely-honed military machines of the Great Crusade. Know then that this is a record of the operational structure, tactical dispositions, and hierarchy of the Fourth Legion Iron Warriors. The Fourth spent the majority of their engagement in the Great Crusade without a Primarch to lead them. Whether through this, or perhaps due to their general desire to adhere to order and logic, the Legion did not deviate from the strictures of the Principia Bellicosa in any major way, instead holding the document as unto law, despite no such restrictions being placed upon them by either the Emperor or the War Council. As the Crusade expanded outwards from Terra, and the other Primarchless legions adapted their structures and tactics to accommodate new styles of warfare, or simply to work with their emerging Legion character, the Fourth held rigidly and resolutely to the Principia. Discipline and order of battle were counted above adaptability or individuality in terms of priority, and the Fourth were expected by their masters to operate both as efficiently as a machine, and also as coldly, to temper themselves against what those of the Legion saw as the flippant heroics of their impetuous cousins in the other Mestartes legions. While the Legion this resolved forged was one that was unquestionably resolute and successful, the sheer lack of flexibility was to become a problem, as the Fourth became known as the Legion that solved any unexpected problem or twist of battlefield of fate, not with quick thinking or keen on the spot strategic insight, but by simply throwing bodies into the fray until the enemy collapsed under the punishing weight of so many Mestartes. While ultimately effective, this nature drew concern, scorn, and even ire from those elsewhere in the Imperium, who viewed the Legion's methods as needlessly bloody and a waste of such precious resources as a start he's represented. Pertoabo's reforms upon assumption of Legion command were sweeping, but did not alter the core of the Fourth in any fundamental way. The Primarch is well known for his rapacious thirst for learning, and during his admittedly brief time with the Emperor was said to have devoured every military treatise either he or his father could lay their hands upon, as well as the entire operational record of the Legion that was to be his. The restructuring was as exacting as it was precise, and, coinciding with the Legion's bloody decimation at the hands of their new commander, illustrated the type of Primarch Pertoabo was, one whose word was law and who would brook no weakness and no excuses. The Legion that resulted was one that resembled many other forces in human history, yet was designed to operate as the epitome of military efficiency. The principal structure of the Iron Warriors was the Grand Battalion. Similar to the chapter as defined by the Principia Bellicosa, the formation nevertheless incorporated a much greater number of armor and artillery elements, as well as a logistical support cadre that eclipsed those of other legions by a vast degree. Both knowing how his Legion had operated and how he intended to employ them, this latter creation of Pertoabos allowed for the Grand Battalion to operate under attritional levels that would cripple a chapter of another Legion. Recruitment of initiates was intended to be constant, no matter what war zone the Battalion was engaged in, which, combined with the style of warfare the Iron Warriors preferred, meant the actual operational strength of each fluctuated wildly, from as low as 500 Astartes to over 5,000. The Legion's pragmatic view of such losses they may incur also meant on numerous occasions understrength Grand Battalions would simply be folded into others operating in the same theater, only to be refounded at a later date. That this could be accomplished with no diminishment of operational quality is itself a testament to the extreme logistical efficiency of the Iron Lord's creation. Additional evidence of this can be found by the sheer quantity, variety and quality of war gear the Legion owned and employed. They had vast stockpiles of munitions and weaponry of almost every variety the mechanic had produced, and thanks to the Primarch's entreaties to certain elements of the priesthood of Mars, the Legion was well provisioned with every type of power armor and Terminator armor mark, showing a special favor to the Mark III power armor and Cataphractii Terminator armor variants of each, due to their resilience and ease of battlefield repair. A remarkable note, however, was the Legion's armor and artillery pools, which encompassed vehicles and field pieces from every single available pattern and design available for Legion as Astartes employment, and in numbers that eclipse those of all other legions, save perhaps the 10th Legion iron hands. The 4th put particular value on the heavier tonnage vehicles, such as the Typhon, Spartan and Mastodon superheavies, but additionally employed large numbers of smaller vehicles, including rhinos and predators, which the Legion viewed as almost disposable due to their ease of manufacture. As previously mentioned, these armor pools were integrated into grand battalion formations at every level, allowing the iron warriors to field more vehicles and artillery more frequently, and in almost unheard of saturation levels, compared to other legions. One example of the latter is the existence of a specialized formation of the store Bzask, the finest artillery operators in a Legion renowned for its skill in such warfare. Siege masters in charge of devices unseen outside of the Mechanicum's Ordo Reductor, they possessed singular battlefield control over all facets of the Legion's artillery train, as well as discretion in the use of dangerous or prescribed weaponry, including atomic, chemical, gravitic, or phosphax munitions. In the case of the latter, the store Bzask additionally was in command of the Legion's destroyer Khadras, which to the fourth was widely seen as a punishment or suicide detail. The formation was outside of the regular Legion chain of command, serving as a specialized siege force that could be broken into formations to be seconded to any grand battalion that required their skills. Another unique formation within the Legion was similarly dedicated to firepower. Tyrant siege terminators were a starties clad in the cataphractii pattern terminator armor, turning them into impervious walking tanks and equipped with cyclone missile launchers mounted atop their carapace. This weaponry granted them tremendous firepower, as well as the ability, thanks to their infantry nature, to rapidly redeploy. Veterans all, the tyrants were often members of the store Bzask themselves, inductees into the Legion's most learned arts of destruction. The Legion was expected by its master to operate as a cohesive integrated force, and it has often been remarked that Perto Abo clearly did not see his sons as individuals. Glory did not belong to a single a starties, no matter his status, but to the Legion as a whole. Every single Legionary in the fourth was expendable to the Iron Lord, a tool in the box, a cog in a great war machine. Yet command needed to be held by individuals, albeit individual members of a great chain stretching from the muddy trench, all the way to the Primark's chambers, bore his flagship, the Iron Blood. The Legion, as mentioned earlier, could absorb staggering losses on a strategic level, and this, coupled with the fourth's stable gene seed and pioneering rapid induction techniques, meant that newer inductees could serve in numerous roles and formations over a very short period of time, depending upon the current tactical situation of the Grand Battalion they were assigned to. Promotion was easily earned through simple survival, as, given the attrition rates the fourth expected as necessary costs of battle, only truly exceptional soldiers could be expected to survive an appreciable period of time. Survival, tempered with talent, earned Legionary his way up the ranks, and those with the capabilities the Legion valued most, rapid data analysis, superior strategic comprehension, and logistical insight soon found themselves climbing the Iron Lord's chain. The Primark rewarded those who could wage war on the scale he preferred, at the strategic, not personal level. Simple martial skills were not enough, and Astartes could best a single opponent with competence, but could he conduct a siege on a grand tactical level. Only those who fell into the latter category earned the scant favor of the Primark, and were rewarded with the title of Warsmith, a role which came to eclipse that of the traditional Praetor, or commander, akin to the Olympian warlords of Perto Abo's homeworld. The Warsmiths of the fourth were unlike the command rolls their cousins held in other legions. Whereas a chieftain of the 16th Legion, Sons of Horus, delegated the resupply of his men to the Mechanicum, a Warsmith was responsible for making sure that every Legionary in his grand battalion had an adequate stock of the correct Bolter ammunition. A Khan of the 5th Legion, White Scars, may only have say over a small area of a much wider campaign, whereas a Warsmith would often be dedicated to the responsibility of planetary conquest. This level of responsibility, coupled with Perto Abo's renowned lack of tolerance for failure, and the 4th Legion's own character, made the Warsmiths an incredibly competent, if grim and dourcast of warlords. The nature of how the Iron Warriors waged war left only the most ruthless of these men alive, and those who managed to distinguish themselves even further were risen to the rank of Triarch, three of which formed Perto Abo's Trident. Ostensibly the Legion's Inner Circle, this trio served as council to the Primarch, but often won that did little to change their master's mind, serving instead to delegate his orders to their own subordinates. To be a Triarch was one of the scant opportunities that those of the 4th Legion had to obtain actual, tangible personal glory, and as such tended to attract only the most politically pitiless of the Legion, earning it the dark reputation amongst Warsmiths who saw no reason in putting themselves in the Primarch's direct firing line, as it were. By the outbreak of the Horus Heresy, the Iron Warriors Legion was estimated to have a total strength of between 150,000 and 180,000 Astartes, placing them in the upper echelons of Astartes' legions by numerical quantity. However, a more accurate assessment is impossible to assay as the Legion was often split into numerous sub-formations, sub-deployments, and garrison operations, scattered throughout the Imperium and increasingly prevalent in the latter years of the Great Crusade. In addition to this, the Iron Warriors possessed a substantial void fleet of several hundred capital ship classes and thousands of cruisers, comparable to that of the 7th Legion Imperial Fists, with which they were so opposed, that these two legions would soon come to clash at the fateful Battle of Fowl, would serve as bloody testament to the rivalry that they had developed in 200 years.