Changes

Following the action at Phall and the [[First Siege of Hydra Cordatus|reduction of Hydra Cordatus]], the [[Space Marine Legion|Legion]] under [[Perturabo]]'s personal command would journey with [[Fulgrim]] to the [[Crone World]] of [[Iydris]], pursuing an ancient weapon known as the [[Angel Exterminatus]]. However , the [[Battle of Iydris|entire affair]] was a ploy by Fulgrim to achieve [[Daemon Prince|daemonhood]].{{Fn|14}}

After this incident [[, Perturabo]] and his Iron Warriors found themselves trapped by the singularity in the heart of the [[Eye of Terror]]. In a desperate gamble, their fleet dove straight into the heart of the Eye of Terror, and were transported far across the [[Warp]] to the [[Tallarn]] System. Once arriving at Tallarn, Perturabo was made aware of the [[Cursus of Alganar|Black Oculus]] (also known as the ''Cursus of Alganar'') hidden beneath the planet, and he immediately drew up plans to [[Battle of Tallarn|acquire it]].{{Fn|23}}

The intended hit-and-seize raid turned into a protracted conflict, as both the Traitors and the [[Imperium]] poured war material to their respective allies on [[Tallarn]], neither willing to admit defeat. Over a million armored vehicles fought across the desert, which is reckoned as the largest tank confrontation in Imperial history, until eventually the Iron Warriors were forced to retreat without the [[Cursus of Alganar|Cursus]].{{Fn|5}} So great were their losses that Perturabo had to launch a [[Iron Shackles|mass recruitment program]] to replenish their strength in the aftermath.{{Fn|79}}

After [[Battle of Tallarn|Tallarn]], the Iron Warriors were assigned to guard worlds to the rear of [[Horus]]' front that since the death of the [[Ruinstorm]] were now threatened by the advance of the [[Ultramarines]]. Many of these worlds served as the Traitor's chief supply line. Overextended, under-supplied, and engaging in thankless bitter sieges against the forces of [[Roboute Guilliman]], the Iron Warriors took heavy losses and found themselves in a situation similar to that of the [[Great Crusade]].{{Fn|26}} This situation was interrupted when [[Perturabo]] received orders to find [[Angron]] and muster at [[Ullanor]] in preparation for the [[Siege of Terra]]. Despite having to abandon large amounts of warriors and worlds for which they bitterly bled for for many years, Perturabo dutifully obeyed. Though many Iron Warriors were lost in the ensuing redeployments, Perturabo succeeded in arriving at Ullanor with Angron and his [[World Eaters]].{{Fn|26}} During the [[Siege of Terra]] , Perturabo became the face of Horus' war to the loyalists, engaging in the ultimate siege against his rival brother Rogal Dorn. The Iron Warriors led the assault against the [[Lion's Gate Spaceport]] and [[Gorgon Bar]] during the battle.{{Fn|52}} Hopwever Following the setback at the [[Saturnine Wall]], Perturabo began to despair over the state of his allies. All save he and the Iron Warriors had by now fully fallen to Chaos, and with his warriors marched all kinds of [[Warp]] abominations. Perturabo realized realised that the war was no longer one of Legion vs. Legion and the ultimate test against his brother Rogal was now tainted. The final straw for Perturabo came after Horus informed Perturabo that he was to disperse his Iron Warriors amongst the various warzones and that his position was to be taken over by [[Mortarion]] and the [[Death Guard]]. Finally having had enough, Perturabo ordered the Iron Warriors to evacuate Terra and withdrew to the ''[[Iron Blood]]''.{{Fn|70}} Some Iron Warrior contingents refused to abandon the campaign or were just left behind by their comrades, and would keep fighting on Terra until the siege's conclusion.{{Fn|89}}{{Fn|90}}

In the end, [[Horus]] was defeated by the [[Emperor]], and the bulk of the Iron Warriors retreated into the [[Eye of Terror]], while the rest sought to defend their scattered empire across [[Imperium|Imperial space]]. Their "[[Empire of Iron]]" continued to be a thorn in the [[Imperium]]'s side for a substantial time. Jointly assaulted by both the Imperial Fists and the Ultramarines, [[Olympia]] itself held out for two years. Eventually, the Iron Warriors triggered their own missile stockpiles when defeat was near, transforming the planet into a barren wasteland that, like the other Traitor Legion homeworlds, was declared ''perdita''.{{Fn|1d}}{{Fn|72}}