From Halopedia, the Halo wiki
He participated in the Battle of Sector Six during the Battle for Earth, retrieving a laser target designator to extrapolate SPARTAN-117's landing co-coordinates. Corporal Rymann gave Hartley covering fire and the two troopers evacuated in a Warthog. Hartley rode in the passenger seat, providing suppressing fire against the Covenant Loyalists. During this escape, Hartley was hit in the abdomen by a Spiker round. The Warthog was then rerouted to the nearest medic, who was in Sector Six, attached to another Marine outfit which was under heavy fire.
When the Warthog arrived at the Marines' position, a corpsman, R. Coney, attended to Hartley's wound, removed the Spiker round from his abdomen, and applied biofoam. Meanwhile, Rymann was killed by a Brute Chieftain with a Gravity Hammer. With the Master Chief's landing only minutes away, Hartley was able to acquire the Spartan's re-entry path using the scanner he had retrieved earlier and pass along the information to the rescue team. Once the SPARTAN's position had been fixed, the order to fall back was given; Hartley was able to retreat and was last seen sitting inside the entrance to a UNSC bunker as the doors closed behind Corpsman Coney and Private Scottlee.
Despite his wounds, he was capable of aiming the laser designator and then making his way inside the bunker without any support; it is thus likely that he returned to action.
Hartley's helmet visor is tinted orange, unlike most ODSTs. This is reminiscent of the MJOLNIR ODST helmet.
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