Event Name: 
The Kynazar Invasion

Location: 
Segmentum Pacificus

Date: 898 M30 - 912 M30.

A brief overlook:
The exact date that the Kynazar fleets poured out of a sector of the Halos Zone into Segmentum Pacificus is unknown, but their scourge came at an inopportune time for the Imperium. With an upsurge in the Rangdan xenocides and a dozen smaller, historically overshadowed campaigns across the Imperium, there weren't any major Legion presences in the relatively peaceful and stable Segmentum Pacificus at the time. While the Segmentum was fully staffed by Imperial Army forces (both military and naval) the scale, brutal tactics and the wide range of abilities of the Kynazar was well beyond what they were expected to be able to deal with. Imperium tacticians for the opening years of this campaign were inclined to divert resources and Legion forces that could be freed up towards the western boarder of Segmentum Solar, deeming Pacificus to be a lost cause and that the counter attack would start in Solar. 

The discovery that this xenos race were the source of the 'Brood Cults' that the Imperium had been encountering for years, alongside their genestealer masters, served to answer some questions that had been held for some time... alas, those 'Brood Cults' in the Pacificus region only made the situation worse as they fully committed to the cause of the Kynazar to unleash as much havoc as possible and betray defensive efforts.  

While many Imperial Army Expedition forces met the Kynazar in battle in both space and on ground and were overwhelmed, four Imperial Army Expeditions independently met prongs of the advancing Kynazar forces and emerged victorious. While these individual victories of Lord Commander Sun-Sin, Lord Commander Horatio, Master of the Fleet Isoroku and Captain Varkarian did little to stop the Kynazar invasion, this would be simply be the start of the legendary careers of each of these men; The presence of not just one military genius, but [i]four[/i] of them raising to the occasion during what could have been one of the darkest hours of the Imperium would would become a symbol of the Imperium's destiny to rule the universe.  

Working with each other and rallying all elements of the Imperial Army forces in the Pacificus to their banners as they could, the four guardians of the Pacificus (as they would be known for propaganda reasons) turned what would have been an utter disaster for the Imperium into a workable (though dire) situation. While they were unable to stop the advance of the Kynazar completely, their efforts to hinder their movements, supply resistance on occupied worlds where the population were still alive and inflict damages to their fleets and ground forces reduced what had been a blitzkrieg of an invasion that threatened to shallow the whole western Segmentum of the Imperium within less then a handful of years to a slow, planet by planet crawl.

The countless imperial lives lost during this brutal defense would not be in vain. With the time bought, Legion and Imperial Army elements from other segmentums were able to be rallied in numbers to repel the invaders. While it would take another decade before the Imperium to reclaim all the ground that had been lost and the last known Kynazar fleet destroyed, the first four years of the invasion would be considered a major, through bittersweet victory for the Imperial Army. The death toll of Imperial Army elements was high, with all planets the Kynazar had touched suffering from massive depopulation, if not the outright destruction of all life, both human and xenos alike. Many worlds were last barren husks as the Kynazar consumed all biomass from them.

While the invasion could have proven far worse to the Imperium at large if it wasn't for the heroic efforts of the Imperial Army, optimistic estimates suggest that it will be several centuries (with more pessimistic estimates suggesting over a millennium) before the population of Segmentum Pacificus starts to reach the levels that it had been prior to the Kynazar invasion.