MOS refers to “military occupational code” or “military occupational specialty code.” Consisting of nine characters, it’s used in the United States Army and United States Marines to specify jobs. The United States Air Force has their own separate code for this purpose, which is the Air Force Specialty Codes (AFSC), while the United States Navy has a different system of ratings and designators which are used in conjunction with its Navy Enlisted Classification system (NEC).
When the MOS was first created, it consisted of just 3-5 digits. The first two digits identified the field code, while the third digit was a sub-specialty code, the fourth digital was the job title, and the fifth digit was the soldier’s special qualification identifier (indicated the soldier’s specialized training). The fifth digital, however, was “o” if the soldier did not have any specialized training.
Today, the U.S. Army and Marines use a nine-digit MOS code. The first two characters are numbers, with the third character being a letter. The two-digit number refers to the solder’s career management field. Rifle infantrymen, for instance, are given the two-digit numbers 11. The following letter is also associated with this identification, with “Z” reserved for “senior sergeant.”
The fourth character in the MOS code identifies the soldier’s skill level. This number ranges from 0 to 6, with 0 referring to soldiers who’ve undergone training for award, 1 referring to privates, 2 referring to sergeants, 3 referring to staff sergeants, 4 referring to sergeant first class, 5 referring to master sergeants, and 6 referring to sergeant majors.
The fifth character in the MOS code can be either a letter or number, and is associated with special qualification identifiers.
The sixth and seventh characters in the MOS code are additional skill identifiers. Like the fifth character, they can be either letters or numbers, but they are only associated with specified MOS.
The eighth and ninth characters in the MOS code are two-letter requirements that are used to identify language. If a soldier has a special language skill, he or she will be assigned the appropriate code via these characters.