World Eaters - Pre-Heresy: At its creation, the XIIth Legion, like almost all the Space Marine Legions of the time, followed the so-called "Terran Pattern" of organisation as formulated by the Imperial Officio Militaris at the outset of the Great Crusade.But even in this earliest period the Legion's procurement and outfitting showed a considerable bias towards direct assault and operations within the close and deadly confines of the kinds of battlefields designated as "Zone Mortalis" in Imperial strategic doctrine. During Angron's transition of command, this would continue, and the Legion's organisational structures were kept largely intact but often further streamlined, with its echelons being biased in make-up towards line infantry formations.These formations were a hybrid of tactical/close assault troops for the main part, supported by dedicated heavy assault units such as Terminators and specialised units such as Land Speeder squadrons. This organisation lent itself well to a highly aggressive strategic posture and belligerent tactics, which while extremely costly in terms of casualties, were also highly effective.The rank structure of the World Eaters under Angron remained simple and direct, the Primarch having little but scorn for the trappings of elites and pointless accolades and titles. It is said that Angron refused even to be addressed as "Lord" by his Astartes, but he did see the virtue of a reliable and transparent chain-of-command in war.The original War Hounds Legion was also known for its harsh enforcement of internal discipline and the hot-blooded temper of its Legionaries. Command within the Legion was gained through a mixture of martial prowess on the battlefield and displays of leadership on the front line, with specialists singled out by aptitude early on.No rank or role within the Legion was exempt from the expectation that they would fight as hard as the rest, however, nor was the desire to grapple with the foe and cut them down by blade-stroke discouraged if the opportunity arose, be the Space Marine in question an Apothecary or Artillerist rather than a frontline fighter.Compared to many of the other Astartes Legions, order and discipline did not come as naturally to those of this gene-seed heritage as might be expected. Tempers often seethed, slights perceived or real were met with anger and more often than not violence would result should a World Eater's sense of honour be impugned.Any officer of the Legion knew they were expected to back up their authority by force if needed, and the punishment of infractors by an officer's own hands was the Legion's way. To disobey an officer's order in battle was a death sentence to be carried out without delay.Trial by combat soon became the Legion's preferred route for settling disagreements within its ranks, and bloodletting by warriors in open discord was an honourable thing both in Angron's eyes and that of his Legion. Here also could one of higher rank be challenged for the right of command, although such rare contests were always to the death.In the aftermath of the betrayal at Istvaan III, the World Eaters Legion, under their savage Primarch Angron, became ever more insular as a Legion and uncontrollable on the battlefield, proving a double-edged sword even to their allies. The psycho-surgery rife within the Legion became even more widespread and extreme in its use, and the Neophytes inducted with ever-increasing pace into the World Eaters' ranks to replace the fallen were cerebrally mutilated with the Butcher's Nails implants as a matter of course.All-out infantry assaults supported by fast moving armour, with the aim of immediately closing into bloody melee with the foe, had always been a hallmark of the Legion, and now became often their goal; carnage for its own sake beyond any strategic objective to the contrary.At the time of the Istvaan III Atrocity, a precise estimate of the World Eaters' fighting strength and disposition was impossible to make. Best estimates of their observed strength were around 150,000 Space Marines, placing the World Eaters in the middle to high levels of comparative strength amongst its contemporary fellow Space Marine Legions.The World Eaters were also well-supplied and supported by the Legio Audax (Ember Wolves) Titan Legion and a fleet of at least sixty capital class vessels. It is commonly estimated that of all the Traitor Legions that had fought at Istvaan III in the purge of the Loyalist faction within their ranks, it had been the World Eaters who had suffered the greatest casualties, with well over 35,000 World Eaters Legionaries believed to have met their deaths on both sides.Aside from the many wounded, it is recorded that a number had succumbed entirely during the protracted fighting to an insane bloodlust and had to be forcibly restrained and removed back to the World Eaters fleet for containment.