202M42 – The light of the astronomican grows so weak out on the eastern fringes of the Imperium that the realm of Ultramar becomes essentially cut off from the rest of the Imperium.
213M42 – The technology within the Golden Throne finally suffers catastrophic failure and gives out. While kept absolutely secret by the High Lords of Terra, the Emperor dies. The guiding power of the Emperor now gone results in the Astronomican losing focus and the Imperium is plunged into turmoil.
213M42 – Warp travel is still possible but only very short distances can be attempted and even then the accuracy and safety of the journey is greatly reduced. More ships are lost and systems become isolated as humanity is reluctant to venture into the warp.
213M42 – Perceiving a threat to Terra will be imminent the High Lords send out emergency telepathic messages to any and all Space Marine chapters requesting their immediate return to the Sol System with as much haste as is feasibly possible. The Ultramarines do not receive news of the Emperor’s death or the request for aid as they are just too far from Terra.
251M42 – A hive fleet, the largest ever recorded at almost three times the size of hive fleet Behemoth, designated ‘Goliath’ enters the eastern edge of the Imperium. Marneus Calgar sends emergency requests for immediate assistance to any and all Imperial forces and space marine chapters able to respond.
251M42 – Responding to the call for aid from their founding chapter the descendant chapters of the Doom Eagles, Novamarines, Praetor’s of Orpheus, Sons of Guilliman, Sons of Orar, Mortifactors, Howling Griffons, Marines Errant and Fire Angels all divert the entirety of their chapters to Ultramar to assist in the defense.
259M42 – After an almost 9 year campaign of hit and run strikes, delaying actions and rearguard battles the hive fleet finally reaches Macragge.
260M42 – By this time the strength of hive fleet Goliath is much reduced but still a massive threat. The 2nd Battle of Macragge lasts for little over 6 months.
260M42 – Calgar is killed while defending the body of the primarch Roboute Guilliman in the Temple of Correction during the siege of Hera. In a cruel repetition of history the entire Ultramarine 1st company including Captain Agemman is destroyed during the siege and legend tells of how Calgar himself killed five tyrants before finally succumbing to his wounds.
260M42 – The 2nd Battle for Macragge finally starts turning in favour of the Ultramarines. Calgar’s sacrifice tore the heart from the Tyranid attack and the swarm began to lose its cohesion.
261M42 – Almost a year passes before the last of the hive fleet is rounded up and crushed. The surface of Macragge is a far cry from its previous form, now just a blasted rocky wasteland. With the rest of the realm similarly in tatters.
261M42 – With the death of Calgar and Agemman, Captain Cato Sicarius becomes Chapter Master of the Ultramarines.
261M42 – Dubbed the Conclave of Hera the chapter masters of the ten space marine chapters present meet in the shadow of their shared primarch to discuss the futures of their respective remaining chapters.
261M42 – During the conclave the psychic message is finally relayed to the Ultramar system informing the chapters present of the doom that has befallen the Imperium. The focus of the meeting now changes from chapter matters to the future of Mankind as a whole.
261M42 – The conclave lasts 3 more weeks, during which a number of momentous decisions are reached. First of which is that it is agreed the Imperium as it stands does not represent what the Emperor had originally envisioned for mankind. Secondly that while far from being the ideal utopia the realm of Ultramar was a much closer model of how the Imperium should function and exist. With the Ultramarines and their successor chapters being the sons of Guilliman who in turn was the embodiment of the Emperor’s soul they agree to take it upon themselves to transplant the system employed previously in Ultramar and apply it to the Imperium at large now that Ultramar lies in ruins. As such they need to return to Terra.
272M42 – With the strength of all of their forces restored the unified ten chapters undertake the long journey to Terra ready to rebuild Ultramar throughout the Imperium.
290M42 – The boundaries of the Imperium has steadily continued to shrink. Every year outlying system went dark and were lost to either lack of supply or because of alien encroachment. The boundaries of the Imperium are now under 40% of their original reach. Space Marine chapters are constantly fighting rearguard actions all across the galaxy slowly retreating to Terra or either isolating themselves and garrisoning their homeworlds.
298M42 – In response to the critical situation all of the successor chapters of the Imperial Fists reform with their parent chapter and the Imperial Fist Legion is reborn.
300M42 – Following the Imperial Fist example the Blood Angel successors reform with their First Founding brothers. Both chapters are openly relieve to have thrown off what was perceived as the shackles imposed by Guilliman 10,000 years before.
318M42 – It takes almost 50 years but the Ultramarine coalition finally near Terra. The High Lords panic, unaware of the war fought against hive fleet Goliath they believe that the Ultramarines refused the call for aid sent 100 years ago, have seen the reformation of the Legions and have now marched on Terra to seize power. They immediately warn the Imperial Fist Legion defending Terra.
319M42 – As the Ultramarine coalition arrive in system they receive the ultimatum sent by the High Lords and the Imperial Fists; to immediately lower shields, power down all weapons and to surrender themselves to the authority of the Fists.
319M42 – Naturally taking this order to be the utmost affront to their honour and intentions the Ultramarines refuse. They see this as absolute proof that the High Lords no longer have the best interests of the Imperium at heart and are only concerned about saving themselves and maintaining their own power. Repeated attempts by Sicarius to reason with the Imperial Fists and have them see reason comes to naught. The Imperial Fists only view the Ultramarines actions as hostile and refuse to yield.
319M42 – It is unclear as to who fires the first shot but within moments of the opening lance shots both fleets unleash all their firepower and humanity’s 2nd civil war begins.