The player first assumes the role of Private C. Miller of the United States Marine Corps' 1st Marine Division, fighting with Corporal, later Sergeant, Roebuck (voiced by Kiefer Sutherland), and his men from the Marine Raiders, during the Pacific War.

The reasons behind this choice sparked speculation, with theories ranging from the mask's psychological impact on enemies to the possibility of hiding scars or disfigurement. Some fans even proposed that "Ghost" referred to various soldiers, symbolizing an immortal identity irrespective of the person underneath.