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The Forerunner-Precursor war was a conflict in which the Forerunners rose up and destroyed their creators, the Precursors, in a massive war. The entire Precursor species was believed to be eradicated from the galaxy, leaving only The Primordial alive.


Roughly ten million years before the Halo trilogy,[1] the Forerunners were refused the Mantle by the Precursors. The Forerunners retaliated, driving the Precursors out and killing almost all of them.

The Forerunners managed to defeat the Precursors, even though the Precursors were a Tier 0 civilization and the Forerunners were only Tier 1. There are hints that the Precursors allowed themselves to be destroyed—that the Precursors were naive and could not conceive of or defend against retaliation of their own creations.


It was hinted that the Forerunners' betrayal perverted the Precursors, driving them to only create things to suffer, so that they may never retaliate against their masters again.

Of the very few surviving Precursors, different strategies for survival were utilized. Many took the form of a fine, desiccated powder that would eventually allow their resurrection. Age perverted this powder, only bringing disease in those that consumed it. The surviving, insane Precursors cultivated and controlled this disease, creating the Flood to transform the universe in their new, insane image. 



  1. Halo: Silentium, String 15, page 181