Parthorum Xenocide

This article is about a battle in the /tg/ Heresy project, a fan re-working of the Warhammer 40k universe.

Parthorum Xenocide
Date	811
Scale	sector-wide
Theatre	Parthorum Sector
Status	Decisive Imperial Victory
Belligerents
Imperium of Mankind	Osroene Empire
Commanders and Leaders
Hektor Cincinnatus	Empress Etuili Sevoold
Strength
3rd Expedition Fleet	armed forces of the Osroene Empire
Losses
Outcome
Parthorum Stream secured for Imperial shipping

The Parthorum Xenocide was the Imperium's name for the first of its three wars for the worlds of the Parthorum Sector. Only one Osroene-authored history of the conflict exists, in the little-read annals of the Pretender Sevtal Sevoold. Sevoold refers to this conflict as the Cataclysm, for the coming of the Imperium heralded the destruction of his people.

Background

The Parthorum Sector is defined by a long, stable current in the Warp beginning about 30 light years north of Terra and tracing a path north-west. This phenomenon, known as the Parthorum Stream covers a region roughly 250 light years long and 50 light years wide at its median point. Warp travel within the Parthorum Stream is relatively predictable and safe, and in the hundred centuries since its reconquest in the Great Scouring, only a handful of ships have been lost while in transit.

Osroene Empire

The Parthorum Xenocide destroyed Osroene centers of learning and killed the great majority of that race's scholars. Human savants only became interested in the history of the lost Empire long after its annihilation and have struggled to piece together its chronology. It is clear, however, that the realm was long-lived and stable, and judging by the anti-Imperial revolts after the war the Osroene must have been accomplished in the art of ruling over a multi-species Empire. Although the Xenos were not as advanced as the young Imperium, they possessed the Warp Drive and had used it successfully in the tranquil conditions of the Parthorum Stream.

The Imperium

Due to the limitations of calculated jumps through the Warp, the first decade of Imperial campaigns following the Unification Wars created a fairly small interstellar state centered on Sol. The Emperor's construction of the Astronomican on Terra increased the practical Warp jump distance one hundred fold and allowed the Imperium's Great Crusade to reach vast territories, among them the Parthorum Stream. Rogue Traders were quick to move into the area and investigate.

The Imperium had known about the Parthorum Sector for months before Hektor Cincinnatus was finally granted permission to launch a campaign of conquest. Although the Primarch was perhaps the third-most powerful of the Imperium's warlords, after the Emperor and Malcador the Sigilite, he had faced considerable opposition to his plans among the Terran adepts of the War Council. Ever confident, Hektor had begun planning while the matter was still in dispute, drawing on the reports of Rogue Traders Militant. Adela Exard's navigational and cultural records were of particular value, so much so that Exard and her Cruiser Black Joke were among the Rogue Trader forces hired on to augment First Legion during the campaign.

Iuybos Subsector Battles

First Legion's initial objectives fell in the southern reaches of the Parthorum Stream, later known as the Iuybos Subsector. The Osroene were aware of the limitations of their technology and relied on strong planetary defences to hold up invaders until one of their great fleets could arrive and decide the action. Adela Exard had obtained records of such relief actions against Gallvi raiders in popular histories and Hektor Cincinnatus drew up his plans accordingly. Rather than disperse his forces to planetary assaults and risk being defeated in detail, the Primarch's first objective was the "Southern Fleet" that patrolled the Iuybos Subsector.

Battle of Kopt Dara

Hektor dispersed the Rogue Traders under his command to monitor the Iuybos Subsector. As was usual practice, a Space Marine officer held formal command of each vessel, but the ship's original captain took the role of ship's master and guaranteed its smooth running. The sight of Solar-built vessels raised little alarm among the Xenos, who had become accustomed to the presence of Rogue Traders during the preceding months. But despite their innocent appearance, the Imperial vessels were hunting for concentrations of Osroene naval power. Perhaps it was appropriate Adela Exard's Black Joke, now under the command of Markos Priscus, found the Xenos' Southern Fleet docked in the Destoona System at 3057811.M30. Priscus immediately ordered his Astropath to signal the First Legion's HQ that their quarry had been discovered. The arrival of Hektor Cincinnatus' naval force is timed to 2104811.M30.

If the presence of the Black Joke had not aroused suspicion, the Osroene reacted promptly to the arrival of First Legion's warships. The Southern Fleet made haste for the outer planets of the Destoona System, taking up station at the gas giant Kopt Dara. From this position, the Osroene believed themselves well-sited to plot intercept courses against the invaders. It was a pleasant surprise for the Xenos that their enemies were willing to meet them at Kopt Dara, but the effectiveness of Hektor's void tactics ruined such warm feelings. The Monarch of the Void, leading one of two Imperial columns, was the first vessel to come under fire at 2125811.M30. The First Legion's squadrons broke through the line of Osroene ships orbiting Kopt Dara. Two semi-connected melees ensued. The smaller, at the rear of the Osroene line was quickly won by a superior Imperial force led by Orion Mucius. The second, larger part of the battle centered on the two flagships and raged for longer, but the arrival of Orion Mucius's forces tipped the battle in favour of the Imperials. The action was over in less than a Terran hour. Following salvage and scuttling efforts, the Imperial fleet was underway again at 2126811.M30, moving out to jump points and then back through to warp to Sol. Only Black Joke remained in system, hiding behind the great bulk of Kopt Dara and monitoring the system via satellites.

Victory at Kopt Dara gave the Imperials a long period of free reign through the southern portion of the Parthorum Stream. Although the Osroene had more warships to reinforce the weakened subsector, their high command would not receive a request for reinforcements until months later, by which time events would have already overtaken their effort to respond. However, the damage incurred at the battle forced the First Legion to spend precious weeks travelling back to Mars to repair their warships. In order to expedite the process, Fabricator-General Kalkas Tygian personally commanded two Mechanicum warships, the Revelation of Victory and the Rites of War to take the place of the crippled First Legion cruisers Mount Ararat and Blessing of Thunder for the remainder of the campaign.

Planetary offensives

Thanks to the efforts of the Mechanicum, the 3rd Expeditionary Fleet was ready to resume its offensive at 1219811.M30. Hektor split his command into three, keeping his own Chrysaspides as a reserve and sending his two Phalanx commanders, the Phalangiarchs Erasmos Sergius and Lysimachos Fabius, into battle.

Imperial Order of Battle

For the outset of the campaign, Hektor had expanded his 3rd Expedition Fleet with the vessels and flotillas of several Rogue Traders Militant. The precise make-up of the forces under command of these idiosyncratic leaders is in doubt and the limited records available often contradict one another. The order of battle described below is therefore somewhat speculative.

• 3rd Expedition Fleet - Primarch Hektor Cincinnatus
  • Naval Task Force - Navarch Orion Mucius
    • Flotilla of Lord Captain Megasu Athon - Syntagma Euthymios Varius
    • Cruiser Black Joke - Ouragos Markos Priscus
  • Chrysaspides - Strategos Hephaestion Horatius
  • 1st Phalanx - Phalangiarch Erasmos Sergius
  • 2nd Phalanx - Phalangiarch Lysimachos Fabius
  • Various Auxilia formations drawn from the Solar Auxilia and The Carlisian Shock Troops.