ONI sees John as a threat because in his current state after Cortanas death, combined with the fact that he is turning into a forerunner due to the librarians modifications. John is training at a facility with other Spartans when ONI officials burst in and fire on the Chief, but Chief kills them all. The other Spartans, confused, decide to help Chief. Chief fights his way through ONI to the headquarters where he finds out the reason. Then, suddenly, the Didact and his promethean army attack. Chief fights his way to the Didact on board a forerunner ship, but is convinced to instead join him. Then the spartan 5s defeat the Didact and bring chief back for rehabilitation, while the rest of the world hunts for him.