Rangdan War

The Rangdan War is regarded as the deadliest conflict in the Imperium's history, in truth eclipsing even the Great Secession that followed it, though that Civil War was a far more bitter affair. In M30.990, forces of the Void Watchers breached the natural barrier surrounding the galaxy, venturing forth into the area known as the Halo Stars. Unbwknownst to them, the Halo Stars were home to a colossal star empire known as the Rangdan, a biomechanical species with technology that rivalled or even eclipsed the Imperium of Man.

What followed was a war of unthought of proportions, Rangdan forces striking on all fronts, seemingly surrounding the entire galaxy, bringing the Imperium onto a total war footing. Astartes and mortals fought and died in unprecidented numbers in every corner of the galaxy, seemingly powerless to stop the Rangdan fleets advancing through Imperial space, commanded as they were by the supreme interlect of the Rangdan Queen, a being who rivalled the Emperor of Mankind Himself in strength, force of will and battlefield mastery.

It was only after the death of the Rangdan Queen and a decade of long, drawn out conflict that the Imperium finally emerged victorious from the war, though there were few who could muster the energy to celebrate. Between twenty and thirty percent of humanity had been exterminated in the war, entire sectors rendered lifeless and barren by the merciless foe. The Space Marine Legions, mankinds foremost defenders, were a pale shadow of their former glory, reduced in strength and limping on with equipment that had been repaired, repaired and repaired again under battlefield conditions.

And yet, for all this, the end of the Rangdan War did not bring about the peace so many had hoped for in those dark days. Instead, the galaxy would have to wait almost a century longer, five years of bitter civil war lay ahead, far more of mopping up the remnants of those self-same defeated loyalists. Only then, when the Imperium stood whole once more under the leadership of the victorious Primarchs, did the galaxy finally know peace.