Changes

The [[Space Marine Legion|Legion]] continued to distinguish itself in the conquest of the [[Sol System]] during the early days of the [[Great Crusade]], winning honours in many battles, most notably in the [[Mehr Yasht]] campaign on [[Venus]], where the IVth Legion was commanded by the [[Emperor]] himself to defeat the deadly [[Litho-Gholem]] armies of the [[War Witches]]. In light of their early successes, the Legion was given first access to new equipment being delivered from [[Mars]]. The Legion led the [[8th Expeditionary Fleet]], which distinguished itself in many campaigns. However, the Legion did not adapt their tactics to the new realities of the expanding Crusade, and was called unimaginative by other [[Space Marine Legion]]s and by [[Horus]] himself. Horus however was impressed by their stubbornness and would use the Legion to fight inglorious but vital campaigns of attrition. They soon became known as the workhorse Legion, relied upon for their tenaciousness tenacity and following to follow orders to the letter. It was during this time that the Legion began to spread itself out, garrisoning many worlds and fighting many smaller campaigns across the expanding [[Imperium]].{{Fn|20a}}

One of the [[Space Marine Legion|Legion's]] most tragic episodes would come in 842.[[M30]] during the liberation of the [[Forge World]] of [[Incaladion]]: The stubborn IVth Legion used their typical tactics of heavy artillery and armored armoured spearheads, and suffered staggering losses in a protracted siege. Nearly 29,000 Legionaries died over the year long yearlong campaign, virtually annihilating the [[8th Expeditionary Fleet]].{{Fn|20a}}

Meanwhile, the Iron Warriors' [[Primarch]], [[Perturabo]], was raised on [[Olympia]], a mountainous planet divided into warring city-states. Because of the rugged terrain, military supremacy revolved around the construction of stone fortresses and the control of strategic mountain passes. Perturabo had an affinity for cold logic and the use of technology which made him a superb military engineer. By the time the [[Emperor]]'s [[Great Crusade]] reached Olympia, Perturabo was warlord to the [[Tyrant of Lochos]]. As was his custom when one of his lost sons was found, the Emperor gave Perturabo rule over his home planet and relocated his [[Space Marine Legion|Legion's]] headquarters there.{{Fn|1a}} Upon taking command of his Legion, Perturabo reviewed the war record of his new forces. After heavily analyzing analysing their record, effectiveness, doctrines, and practices, Perturabo found them wanting. His punishment was [[Wikipedia:Decimation (Roman army)|decimation]]. By lottery, one in every ten Legionaries was chosen to be beaten to death by his comrades. Such would be Perturabo's reign: brutal and unforgiving.{{Fn|20a}}

Even before they were reunited with their [[Primarch]], the [[Space Marines]] of the IV Legion had inherited his military qualities. [[Perturabo]] quickly recruited new troops from [[Olympia]] and embarked [[Fall of the Black Judges|on a campaign]] against the nearby moon base known as the [[Rock of Judgement]], ruled by the [[Black Judges]]. It was a stunning success, though only fragmentary records of it survive in the aftermath of the [[Horus Heresy]].{{Fn|1a}}