These sleeping "guardians" would be awakened at the most critical moment.
Terra's preparations for war proceeded in an orderly fashion, amid an atmosphere of tension and efficiency.
Finally, ten years after the rebellion began, after Horus had swept away all the Imperium's outer defenses, the clouds of war gathered over the Solar System.
Fleet after fleet arrived at Terra, bearing the last hope.
The Blood Angels descended, led by their Primarch, Sanguinius, whose perfection rivaled that of a god. Their arrival was a golden bolt of lightning in the darkness, bringing boundless light and hope to Terra.
Under Jaghatai Khan's leadership, the White Scars returned to their homeworld like a raging wind. Their arrival brought a surge of wild, untamed vitality to the oppressive siege.
Even the Dark Angels, far away on the other side of the galaxy, sent ten thousand elite warriors to reinforce them, led by Corswain, one of their Primarch's personal guards.
The loyalists' strength on Terra reached its peak.
But they were about to face nine fallen Primarchs and their immense, seemingly endless armies of Chaos, composed of Space Marines, daemons, traitorous mortals, and the Dark Mechanicum.
The hour of the decisive battle had come.
Horus chose Terra's outermost and most important gateway, Lion's Gate Spaceport, as his first target.
The task of breaking its defenses fell to Perturabo, Primarch of the IV Legion, the Iron Warriors-a great tactical master whose reputation in siege warfare rivaled Rogal Dorn's.
A clash of steel against steel, a contest of will against will, was about to begin.
Artillery fire sounded the opening notes of war.
Perturabo's fleet blotted out Terra's skies like dark clouds. Guided by the Iron Warriors Primarch's cold, precise calculations, tens of thousands of guns unleashed what could be called the fiercest, most accurate saturation bombardment