Private
From Halopedia, the Halo wiki
Template:Ratings Template:Rank Infobox
Private is the lowest enlisted rank of the UNSC Marine Corps and UNSC Army, and is equal in rank to Crewman Recruit in the UNSC Navy. The majority of Marines begin service as a Marine unless otherwise noted by their MOS or performance in boot camp. Privates do not have an insignia. The next rank up is Private First Class.
Unlike other branches of the Defense Force, the Marine Corps gives more responsibilities to its lower ranks. If necessary, even a Marine Private can lead a small-man fire team.
UNSC Army
An E-1 in the UNSC Army is officially known as a Private E-1, as opposed to simply Private.