John Forge was an accomplished, but hot-tempered sergeant in the UNSC Marine Corps, noted for both his skill in the field and his tendency to get into conflicts with superior officers. Forge was assigned to the UNSC Spirit of Fire in early 2531, which almost immediately after became involved in the Harvest Campaign. During the conflict on Harvest, Forge and the Spirit of Fire were forced to leave for Arcadia, after Professor Ellen Anders was kidnapped by the Covenant, led by Arbiter Ripa 'Moramee and the Prophet of Regret. The ship and Forge briefly became involved in the Battle for Arcadia, picking up Spartan-II Jerome-092 and Red Team along the way. Soon after arriving on Arcadia, however, the Covenant forces took Anders to the Etran Harborage, a Forerunner shield world, and the Spirit of Fire followed.
At the Etran Harborage, Forge and the Spirit of Fire discovered both the Covenant forces trying to use Anders to gain access to a fleet of Forerunner Dreadnoughts, and the Flood, who had gotten loose and infested the shield world’s surface. Forge successfully rescued Anders, but it was decided that the only way to keep the Covenant from gaining access to the Forerunner ships was to destroy the entire planet. Using the ship’s Shaw Fujikawa Translight Engine, the Etran Harborage was successfully destroyed, though John Forge was forced to stay behind to detonate it, sacrificing himself for the cause.