From Halopedia, the Halo wiki
This Marine fought and was injured in the Battle of Mombasa on October 20, 2552. He was part of the UNSC Marine Corps unit deployed to the Uplift Nature Reserve near the site of the gravity lift landing zone of the Prophet of Regret's assault carrier. During the battle, his ankle was broken, which drove him mad. He was treated by Private First Class Chips Dubbo behind a ledge where a group of other Marines were taking cover.
The wounded Marine can be found in the Halo 3: ODST campaign level Uplift Reserve. His presence is a nod to a pair of similarly distraught Marines in Halo: Combat Evolved and Halo 3. Unlike his forebears, this Marine is worried about the Covenant instead of the Flood, a theme continued by his Halo: Reach counterpart.
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