Sgt. Hauser served as a UNSC Marine Corps sergeant during the brutal Harvest Campaign, a grueling operation to retake the colony world Harvest from Covenant occupation. His unit, forced into retreat under relentless Covenant assault, regrouped with Spartan-II Daisy-023, who provided critical support against enemy infantry. Hauser then organized the recovery of three Warthogs to forge an evacuation path, personally maneuvering one vehicle while Daisy manned its turret.

The convoy’s progress halted abruptly when a Covenant Elite detonated a plasma grenade, overturning the transports and injuring Hauser. Daisy dragged him from the wreckage, advancing toward an extraction Pelican. As they fled, a Covenant Elite ambushed the group with a Needler, mortally striking Daisy. Hauser and Spartan-II Ralph-103 defied orders to leave her behind, delaying their escape. Covenant fuel rod cannons obliterated the Pelican moments later, claiming all survivors. Hauser’s leadership under relentless fire exemplified his resolve amid the campaign’s chaos, though his earlier service remains unrecorded.