Perturabo - Iron Within, Iron Without: After a brief period in the Emperor's company fighting alongside Him and consuming knowledge of the Great Crusade, its history, war machinery and operations, Perturabo was handed the command of the IVth Legion which bore his gene-seed, and the transition of authority to him was swift and absolute. At the time, around 35,000 Astartes of the IVth Legion had been mustered to create his independent command, with perhaps half that number again scattered across the conquered domains of the Imperium in smaller independent garrisons and detachments bound to their watches and their duties.Having instituted a full review of the IV Legion's war record, doctrines and practices and having compared those with the other Legions, Perturabo found his sons wanting and acted accordingly. His punishment was decimation. For the Legion's failing all would suffer, all were guilty. As the edict of decimation would state, "War is unequivocal, uncaring, unforgiving and blind. Blind also will be the selection of those who will pay the blood price for the greater failure of your record." One in ten of the Legion, determined by lottery, was put to death without honour, a deed carried out by each Legionary's own comrades with their bare hands.At this bloody edict some within the Imperial Court protested, believing that the Emperor had given absolute power of a Space Marine Legion to a madman, while others, more guarded in their criticism, opined only that command had been given too soon to the primarch -- unused as he was to the ways of the Imperium. Loudest of these critics was Roboute Guilliman, primarch of the Ultramarines, who bridled at the ignominy of the deaths to which valiant Astartes -- warriors alongside which his own Legion had often fought -- had been thus consigned. It was a spur of discord between the two Primarchs that, though later eclipsed by other rancours and feuds among the Emperor's sons, would be one that neither would ever forget. All such criticism the Emperor silenced.To those who survived the IVth Legion's self-decimation, the lesson was plain: such was to be the rule of Perturabo, ruthless and unforgiving, and without favour or preference. Death would be the price of failure in Perturabo's service and war was to him a binary equation. Their sin was not that they had failed in the Great Crusade's service -- for by no measure had this been the case, but instead that they had not reached their full potential. It was not enough for Perturabo that they were merely superior, their fault lay in that among the Legions they were not already supreme.Perturabo demanded that his Legion would be a peerless engine of war, and he immediately set about fashioning it into the weapon he desired it to be, a weapon whose edge he would first test against the rest of the Meratara Cluster at whose edge the Olympia Majoris star system sat. There he first overthrew the vaunted "Black Judges" and claimed their once-held domain for the Imperium, before purging the xenos Ecto-Saurids of Verikhonia and subjugating the Renegade Knight-fiefdom of Lyxos, completing his conquest of the cluster.In this last conflict, Perturabo's Legion ended by force a schism that had lasted for millennia back into the Age of Strife between the fragmented empire and its former masters in the Mechanicum, winning the Legion much favour with the Lords of Mars. This period was for the IVth Legion a winnowing; a time of trials and testing at their Primarch's hand.With calculated forethought and savage experiment Perturabo remade the Legion to his own image -- an image not echoing the Olympian or Terran ideal -- but one fashioned purely from his own bleak and unflinchingly ruthless psyche. At the end of the Meratara Custer campaign, the IVth Legion of old was no more, and the Iron Warriors had been forged from blood and fire in their place.By the time Perturabo returned again to Olympia with his renamed force, the machinery of his plans was well into effect. In alliance with the Mechanicum, new orbital shipyards and foundries burned with frenetic activity, many had been torn from dead orbits around conquered stars, dragged to Olympia and refitted and expanded to his Legion's purpose. The worlds of the Meratara Cluster too now paid their tribute of flesh and blood to the Lord of Iron to feed his Legion's hunger for fresh warriors, weapons and munitions.All was by Perturabo's hand and design. In the crucible of war, the Iron Warriors had undergone its reshaping, with the changes that had occurred seen in many ways to have amplified what was already present in the IVth Legion rather than changing it beyond recognition; where once the Legion had been ruthless in its willingness to accept losses in return for victory, now it was utterly driven to the point where such considerations were as beneath it as mortal fear.War had become a deadly equation which the Iron Warriors were supremely suited to solve; a relentlessly unyielding engine of war, a beast of steel and fire which swept worlds clean and devoured whole armies.At the head of a newly constituted force, the 125th Expeditionary Fleet, into which Perturabo drew the bulk of his Legion's strength, the Primarch had command of a force which quickly became the battering ram of the Great Crusade. As they fought alongside each of their fellow Legions in turn, they gained an unmatched reputation for brutal efficiency in battle, mastery of armoured warfare and as artillerists without peer among the Legions.It was said of the Iron Warriors that there was no fortress built by the hand of humanity or that of the xenos they could not smash down, no stronghold they could not storm and no army they could not drown in its own blood through shot and shell.