About Military Occupational Specialties (MOS)
The U.S. Army used alphanumeric codes (e.g., 11B10, Light Weapons Infantryman) to identify the Military Occupational Specialty (job) each person held. The MOS that a person was qualified in was called the PMOS (primary MOS), while the DMOS (duty MOS) was the job they actually held at a given time.
Different MOS coding systems were used for enlisted, warrant officers and officers:
Enlisted codes consisted of five digits. The first three (e.g., 11B) indicated the position while the fourth and fifth indicated the relative level:
xxx10 – basic Infantryman (E1-E3) = 11B10
xxx20 – specialist (Specialist 4th Class, E-4) = 11B20 (Note: some SP5s were 20s, e.g., 63B20, 91B20, 94B20)
xxx30 – team leader, specialist (E-5) = 11B30 (A number of SP5 positions had “30” MOS codes, including 64C30).
xxx40 – noncommissioned officer (Sergeant E-5, Staff Sergeant E-6, Sergeant First Class E-7) = 11B40
xxx50 – senior noncommissioned officer (E-8, E-9) = 11B50 (or, as we shall see, 11B5M, first sergeant)
Where the individual held a Special Qualification Identifier (SQI) for special training or skills, the last character was an alphabetic SQI Code that indicated the qualification (e.g., in 11B1P. the “P” indicates “parachutist”)
Warrant Officer MOS Codes were also 5 digits, but the first four (e.g., 631A) indicated the position, with the last available for an SQI suffix.
Commissioned Officer codes were numerical; four digits indicated MOS (e.g., 1542, Infantry Officer) and an optional one digit SQI prefix indicated a special qualification (e.g., 71542, Jump-qualified Infantry Officer).
The U.S. Army changed the MOS coding structure sometime in the 1980s, so the MOS codes which we held are now part of history. While MOS codes can be useful especially when visiting the Wall or searching through the casualty database, they can be fairly hard to find these days.
Most of us in Charlie Company were 11B or 11Bravo, or AKA Straight-leg Infantry, or Ground-pounders, or The Queen of Battle (Inside joke), or in one specific case “A Perimeter Grunt.”