Editing Ultramar (section)

==The Plague Wars==
In M42, Ultramar's formerly idyllic existence was shattered by a Death Guard invasion led by Mortarion himself. Three systems to the galactic north of Ultramar were corrupted by influence of Nurgle and its planets are turned into staging grounds for the invasion of Guilliman's mini-Empire. This had apparently begun a few decades prior to the conclusion of the [[Indomitus Crusade]]. Surprisingly, Guilliman did not end the crusade upon hearing about the invasion of Ultramar. He wished to remain in command of the Imperium at large and knows he can do more good that way. He therefore left it to his sons to hold the line until his return. [[Imperium Secundus|Shows he's learnt something from the Heresy.]]
 
Mortarion's already large invasion force, bolstered by mutants and cultists from the [[Scourge Stars]], was accompanied by [[Typhus]] and his [[Plague Fleet]] alongside the Great Unclean One [[Ku'Gath]] Plaguefather and his Plague Guard. Their strategy concentrated on taking and holding a few major planets such as Iax, Espandor and Konor. They only launched raiding attacks on the less defended ones, withdrawing before Astartes were deployed.
 
The Espandor system was devastated. All planets in the system besides the main planet were taken; the Ultramarines bitterly contested Espandor Prime and would do so until they were later relieved. One of the Plague Guard would lead this attack, a [[Daemon#Greater_Daemons|Greater Daemon]] named Qaramas. The partial conquest of the Espandor system opened up the gateway for the rest of the invasion fleet to surge into Ultramar.
 
Iax was overrun by daemons of Nurgle as the bulk of the invasion force came to bear upon it. It had been converted into a hospital world earlier in the war and was therefore susceptible to infiltration by the heralds of Nurgle despite its stringent quarantine measures. This would be the base of operations for the entire invasion and conquest of Ultramar as Mortarion, the Death Guard and the rest of the Plague Guard would gather here.
 
Macragge suffered bouts of Chaos-induced unrest as Mortarion led probing attacks on the Ultramarines' homeworld. While this did not lead to any widespread destruction or damage to critical facilities, these incidents caused a drop in civilian morale and wasted Marneus Calgar's precious time on peacekeeping missions and displays of force to shore up confidence amongst Macragge's civilians.
 
Typhus and the Plague fleet had overrun and taken one of Ultramar's star forts. He was later directed by Mortarion to attack the Ultramarines training world of Parmenio. Konor would come under attack as well by the forces of the Death Guard, their aim being to take the crucial system and use it as a launching pad for an attack on Macragge itself. Though that failed miserably when Mortarion re-enacted Star Wars Episode IV with predictable consequences.
 
Guilliman eventually returned to Ultramar from his Indomitus Crusade, bringing with him thousands of Primaris reinforcements. First, he cleanses the Hive World of Ardium in the Maccrage system from the Death Guard. There he discovers that Mortarion was using the Hand of Darkness to craft Plague Engines that were re-animating the dead and turning them into Plague Zombies. He destroys the engine on Ardium and frees the world from the influence of Nurgle. He then landed on Maccrage, bringing with him thousands of Primaris Marine reinforcements and other allies. After taking stock of the situation, he organized the Ultramarines and their auxilia to launch a large-scale counterattack against the invaders. Several loyalist Ultramarine successors also joined the fight, their fleets engaging the Death Guard and doing their best to keep Ultramar's shipping lanes safe.
 
He first set his eyes on Espandor System, which served as the main supply line for the Death Guard invasion. He retook each of the lost worlds and destroyed the engines that were creating plague zombies on each of the planets, freeing them from the influence of chaos and destroying the source of the plague zombies. After a ferocious battle in which the Ultramarines Chapter found themselves fighting side by side with their Primaris brethren for the first time, the forces of Nurgle were routed from the planet, Guilliman decisively ending the battle by killing the greater daemon Qaramas with the [[Emperor's Sword]] and destroying the last Plague Engine in the system. The Espandor system was now essentially cleansed and the forces of Nurgle were cut off from the Scourge Stars.
 
With their supply lines to the Scourge Stars being cut, the Hand of Darkness lost (having been recaptured by the Ynnari after Guilliman informed them of it) their Plague Engines slowly being destroyed (stripping the traitors of their supply of Plague Zombies) and Imperial reinforcements pouring into Ultramar with each passing day, Mortarion found himself on the wrong side of the war of attrition. Guilliman had cut the Death Guard off and was now cutting them to pieces. With this in mind, Mortarion decided to throw all his remaining forces at one target.

Macragge was still too heavily defended for the forces of Nurgle to assault so it was decided that they would target the Ultramarines training world: Parmenio. This battle saw the biggest armored clash between the traitor and loyalist forces during the war. The largest star fort in Ultramar, Galatan, attempted to provide support but was engaged by the Plague Fleet and was boarded by traitor marines, leading to the death of the Novamarines Chapter Master. On the surface, however, the Ultramarines were slowly winning the fight. Guilliman killed Ku'gath's lieutenant Septicus and shattered his Plague Guard, giving the loyalists the upper hand and causing them to make major gains against the archenemy.
 
Guilliman then finally led the relief force to Iax. Not finding Mortarion in either Parmenio or Espandor, he was determined to hunt down his traitorous brother once and for all. The final battle of the war took place here, with Guilliman and Mortarion fighting each other to a standstill amongst the ruins of Iax. Eventually, Mortarion and the Death Guard were summoned back to the Scourge Stars, which had come under threat from the forces of Khorne in what would become the War in the Rift. They withdrew from Iax under the cover of a virus bomb and the forces of Nurgle retreated from Ultramar, but the threat of a renewed attack in the future remains.

After the forces of Chaos withdrew, Guilliman oversaw a period of reconstruction and restoration across the realm of Ultramar. He also gave the Ultramarines the means of creating new Primaris Space Marines and helped complete the reformation of the 500 Worlds. Although his duties would eventually call him away, he ensured that Ultramar would be fortified against future threats hereafter.