The Indomitus Crusade was the great military undertaking that pulled the Imperium back from the brink of collapse in the wake of the Great Rift. Launched by the resurrected primarch Roboute Guilliman, it was a galaxy-spanning campaign to relieve besieged worlds, reopen severed supply lines, and reconquer territory lost when the heavens split in two.
At the crusade's spearhead marched the Primaris Space Marines, a new generation of transhuman warriors unveiled after ten thousand years of secret development. Alongside them fought regiments, war engines, and even the golden Adeptus Custodes, roused from their long vigil on Terra to accompany the Emperor's son into the storm. For a century the crusade fleets ranged across the galaxy, fighting on countless fronts against every enemy of Mankind.
Guilliman's campaign was as much an act of restoration as of war, reforging shattered defences and rekindling hope in a realm that had nearly lost it. When at last the crusade was formally concluded, the Imperium was battered but standing, its forces reorganised and reinforced for the desperate age ahead. Yet the victory was incomplete, for half the galaxy remained cut off beyond the Rift, and the wars sparked in that dark time were far from over. For more, see the Indomitus Crusade.