Second lieutenant
From Halopedia, the Halo wiki
Template:Rank Infobox Second Lieutenant is a junior commissioned officer rank of the UNSC Marine Corps and the UNSC Army. It is the lowest commissioned officer rank, and is equal in rank to Ensign in the UNSC Navy.
Second Lieutenant is typically the entry-level rank for most commissioned officers in the UNSC Marine Corps and Army. A Second Lieutenant usually receives a promotion to First Lieutenant after 18 to 24 months service.
In informal settings, Second Lieutenants are referred to simply as "Lieutenant".