Editing Ultramar (section)

==Shadow Crusade==
During the Horus Heresy, the full might of the Word Bearer and World Eater Legions were unleashed upon the 500 worlds as Horus wished to keep the Ultramarines from interfering with his advance to Terra. Many of the planets in Guilliman's star empire were subjected to ferocious and unexpected invasions.

With almost half of the Ultramarines Legion killed or put out of action after the Battle of Calth, and interstellar communication/travel cut off from one another due to the Ruinstorm Lorgar summoned, each planet was left to fend for itself. Some planets were able to repel the invaders completely. On Astagar, a force led by Lucien Corvo (later the founder of the [[Novamarines]]) managed to win the battle for the planet by destroying a possessed Warlord-Class Titan belonging to the Word Bearers. On others, the Ultramarines destroyed their worlds rather than let the enemy have them. This happened on Percepton, where an outnumbered chapter of the Ultramarines subjected the planet to phosphex bombardment, burning away both defenders and invaders who were unlucky enough not to evacuate in time.

Kor Phaeron would put his own plan in motion to strike at the heart of Ultramar and destroy its core worlds while Lorgar and Angron tore through its outer rim. He planned for an Abyss-class super battleship, the Furious Abyss, to destroy Maccrage, the home planet of the Ultramarines, while the bulk of the 13th Legion was stationed at Calth. This mighty vessel would then join a smaller fleet of Word Bearer vessels in laying waste to the core planets. Fortunately, a small strike force of Ultramarines and Space Wolves would board this ship and destroy it from the inside at the cost of their lives. Without the Furious Abyss, the Word Bearer attack on Maccrage and the core worlds of Ultramar failed.

Lorgar and Angron's main force did manage to conquer 26 planets including the world of Armatura, which had been an Ultramarine recruiting world during the Great Crusade. Accompanying this force were two Abyss-class super battleships as well as the Word Bearer and World Eater Gloriana-class flagships. Things would come to a head on Angron's homeworld of Nuceria, which saw the final battle of the Shadow Crusade. Guilliman and his motley fleet of 40 escort and cruiser-class ships (destroyers, corvettes, strike cruisers etc.), patched together from whatever he could muster after the Battle of Calth, threw itself at the combined spearhead of Word Bearers and World Eaters. Fortunately for the Ultramarines, [[FAIL|three unsupported mega-battleships would prove to be Lorgar's idea of a balanced fleet.]]

At great cost to the 13th legion (12 of the smaller vessels), they managed to bring down Lorgar's flagship, the Fidelitas Lex, by swarming it with about 30 ships. On the surface, the outnumbered Ultramarines would be pushed back and forced to retreat under the unrelenting pressure of two traitor legions commanded by their Primarchs - and by the end of the battle Angron had become a Daemon Prince. Although the boys in blue would end up withdrawing from the battle, this marked the end of the Shadow Crusade as Lorgar considered the [[Ruinstorm]] sufficiently fed and redirected his forces, along with those of the ascended Angron, towards Terra.

More traitor legions would also invade Ultramar space during the Heresy, although they were not part of the Shadow Crusade. For example, a 25,000-strong force of Night Lords that were one of the six splinter fleets escaping the Dark Angels would attack Sotha. Due to the superb strategic defense put in place by the defector Warsmith Dantioch, the Imperial Fist Captain Polux, and the thousand-strong Ultramarines Aegida company, this ended up being one of the most lopsided battles in the Horus Heresy. The invaders suffered near-total losses and were forced to retreat as they learned that Guilliman himself was leading a retribution fleet to Sotha. However, victory was only made possible due to the tragic sacrifice of Dantioch and nearly all of the Aegida Company (the survivors would later go on to become the [[Scythes of the Emperor]]). This would also inadvertently act as the [[Imperium Secundus#Tyranids|impetus]] for the [[Tyranids]] to invade the galaxy several millennia later, though nobody suspected it at the time. In the outer reaches of Ultramar, the [[Death Guard]] would also launch probing attacks on the relatively undefended border worlds. Late into the conflict, the Salamanders strike cruiser, Charybdis, would find the corpse of another Abyss-class vessel in the extreme outer edges of Ultramar space. It seemed as if it were attacked by a large Ultramarine fleet and destroyed when it was boarded and had its warp drive detonated by the intruders.

It is difficult to gauge how many planets were destroyed in total however; a snippet from the Horus Heresy books states that a little over a hundred worlds "died" due to the invasion. It should be noted that some of these worlds did manage to recover from the attack. Most notably Calth which would (ironically) become the perfect home to Ultramar's shipyards in M41 due to the fact that the Word Bearer invasion turned its surface into a smooth and airless planet. Planets such as Armatura were left alone and Parmenio would be the new main recruiting world. As for lives lost, 120,000 Ultramarines died during the Battle of Calth and a further 30,000 presumably died from the ensuing invasion. This left the Ultramarines with 100,000 marines near the end of the Heresy, down from their 250,000 at the start. The losses for the Auxilia were horrendous as well, with 500,000 dead at the Battle of Calth alone.