Iron Warriors - Serried Ranks and Steel Banners: Founded as its brother-Space Marine Legions were on Terra during the closing stages of the Unification Wars which presaged the Emperor's Great Crusade in the middle centuries of the 30th Millennium, considerable surface level detail on the origins of the IVth Legion remains. Its first muster grounds are noted to have been founded atop the wreckage of a recidivist fortress on the Auro Plateau of Sek-Amrak.The warlike gun-tribes, blood grieves and Tek-enclaves in the surrounding area provided the Legion with much of its earliest waves of recruits as the recalcitrant region was brought fully into the fold of Terran Unification, rapidly becoming one of the most stalwart of Loyalist domains.Documentary evidence attests that the IVth Legion's gene-seed showed an above-average adaptability and rates of implant rejection were notably low, particularly in comparison with difficulties in large-scale implantation encountered with other Progenoid types, which would not be eliminated until the acquisition of the Selenar gene-labs of Luna.This advantage meant that the IVth Legion's fighting strength was built rapidly, expanding to several fully battle-ready battalions in size while some of the other nascent Legions were still yet unable to field more than an active century. This in turn meant that the IVth Legion was very swiftly put to active-service alongside the Ist Legion (Dark Angels) and Vth Legion (White Scars).The IVth Legion fought first on Terra in the destruction of the final resisting elements there and then throughout the pacification of the Sol System. Testament to this fact can be found in surviving frescoes in the Imperial Palace, according them with the battle honours of the Cydo-Tyre Orbital, the Zidex Archipelago, Ice Station Echo and Mehr Yasht.The lattermost of these names, Mehr Yasht, is perhaps the most noteworthy as it was the key battle of the punishing Venusian campaign and its citation accords "...the serried ranks and proud steel banners of the IVth Legion..." as going forth and into battle under the direct command of the Emperor Himself to break the back of the deadly Litho-Gholem armies of the Venusian War Witches.It appears that the IVth Legion's early successes were accordingly rewarded with primary resupply of newer classes of weapons and war machines as they were made available from the Emperor's alliance with Mars, as well as a noteworthy short-term increased intake of Terran recruits originally intended for the IIIrd Legion (Emperor's Children), swelling its numbers further to replace ongoing losses accrued in battle. (The difficulties caused by the catastrophic near-loss of the IIIrd Legion's gene-seed to suspected sabotage and a viral blight are dealt with elsewhere in Imperial historical records).It was by this gene-seed adaptability and proven success in battle that the IVth Legion became one of the most numerous of the Legiones Astartes during the earliest years of the Great Crusade, enabling its forces to successfully split between several substantial early Expeditionary Fleets.Most notable of these was the 8th Expeditionary Fleet, in which it formed the key and leading elements. This force conquered or reclaimed twenty-nine coreward system-clusters and annihilated several interstellar xenos realms in a protracted eleven-standard-year campaign which played a key part in the establishment of the Imperium's control of the Segmentum Solar.All were achievements for which it was recognised and commended by the Emperor in turn. The IVth Legion took from the 8th Expeditionary Fleet the emblem of the Winged Bolt as its first heraldic device and displayed its battle honours with pride, carrying them as vexilla standards before the dauntless columns of its Legionaries as they advanced into shot and shell across dozens of worlds conquered by the force of the IVth Legion's arms.As the forces of the Great Crusade went beyond the boundaries of the Segmentum Solar, pushing onwards with the Great Crusade's expansion, several sources note that the IVth Legion -- which was not to be united with its primarch until the late 840s.M30 -- had quickly lost any specific ties to Terra, either by culture or indeed recruit intake pattern, although as it pushed ever onwards at the forefront of expansion, its military formation remained rigidly unchanged.The IVth Legion's adherence to the organisational structures, fighting methods and panoply laid out as a pattern for the Legiones Astartes at the very beginning of the Great Crusade remained consistent, with no fresh "stamp" of a new culture brought by interaction with a primarch for many Terran years.As a result, its methods of warfare too went largely unaltered, regardless of circumstances or enemy, and the Legion was wont to overcome any obstacles or difficulties they faced with relentless and meticulously applied force of arms alone rather than cunning stratagem or bloody-handed heroics.These combined factors set them out as being increasingly different from many of their brother-Legions, as by this period of the Great Crusade, most Space Marine Legions were now divergent from the basic Terran pattern set as the template during their first muster, regardless of whether or not they had been united with their primarch.Unlike the IVth Legion, their brother-Legions had, within the space of a few short solar decades, evolved to demonstrate recognisable and, in some cases, extreme character traits and modes of warfare of their own that erred considerably from the basic pattern, and to these the constancy and pragmatism of the IVth Legion's operations stood out in contrast.These traits labelled them as unimaginative, mechanistic and even honourless fighters in the minds of certain other Space Marine Legions and their masters -- not least of all Horus -- it has been said.Conversely, to some within the Great Crusade's High Command these traits were positive factors, making the IVth Legion arguably more reliable in deployment than some of the more esoteric Legions and more ready to meet commands from outside their own Legion without complaint.Accordingly, the IVth Legion was increasingly used to fight often inglorious but vital campaigns of backbreaking attrition and drawn-out bloodshed, and they became in short a "workhorse" Legion, relied upon both for their martial power and their reliability in following orders to the letter.Furthermore, whereas substantially-sized Legions such as those of Leman Russ of the Space Wolves, Ferrus Manus of the Iron Hands, and Horus and his Luna Wolves refused to split their forces at the behest of minor -- and merely Human -- theatre commanders, the IVth Legion did not baulk at any duty to which they were lawfully tasked.They fought repeatedly in thankless sieges and protracted suppression campaigns which demanded the might of the Legiones Astartes to secure victory, but which carried little renown.They also undertook the garrisoning of worlds too dangerous for any but the Legiones Astartes to hold. The IVth Legion had a single charted course whose direction lay in the hands of others; to follow the orders of the Great Crusade whether it was tasked to go and to fight and die as it must. From war zone to war zone the IVth Legion went without respite or fanfare, taking bleak pride in its largely thankless work.So the Legion subtly began at last to change, just as its formerly great strength in numbers was bled through attrition and its brother-Legions outpaced it in glory.With the benefit of hindsight, it is perhaps possible to see that it was during these times, even before they were united with their primarch, that a subtle wedge had been driven between the IVth Legion and its brother-Legions, creating a fracture that would only worsen in time.