New MOS Database launched! image

New MOS Database launched!

Our online database of World War II Military Occupational Classifications for Enlisted Personnel is now live on the website. Read about our efforts to digitize and launch it here.

Strictly GI member and webmaster Ben has been hard at work since we launched the new website a few weeks ago, working on a new feature that he's been interested in for many years; a searchable, digital database of Military Occupational Classifications ("MOS") codes, and we're pleased to say that he's now completed the database and made it live on the Strictly GI website. 

The new World War II Military Occupational Classifications database contains nearly 600 MOS codes for Enlisted personnel, including their official designations, roles and responsibilities, as well as alternative names and substitute codes (where applicable). Each code was transcribed by hand (well, computer) from War Department Technical Manual TM 12-427 (dated 12 July 1944): "Military Occupational Classification of Enlisted Personnel", and provides a unique digital record of the contents therein. It represents an excellent source of information, both for researchers and living historians alike, documenting and prescribing the original roles and responsibilities for Enlisted personnel within the US Army during World War II. 

The following information has been taken from the introduction of TM 12-427, and gives some insight into the purpose and use of Military Occupational Classifications during World War II.


Proper classification of Enlisted Men will facilitate the:

  1. Conservation of available skills through maximum utilization of physical capacity, leadership qualities, experience, education, training, skills, and aptitudes.
  2. Construction and development of Tables of Organization and other personnel manning tables with respect to the kinds of military occupational specialists needed by a unit to perform its mission.
  3. Requisition and assignment of Enlisted Men qualified to meet the requirements of a military assignment.
  4. Selection of Enlisted personnel for retraining or vocational rehabilitation in preparation for continuation of service in the Army or for return to gainful civilian employment.
  5. Separation of individuals from military service and rational demobilization to achieve fullset utiliziation of military occupational training and experience upon return to civilian life.

Definition of a Military Occupational Specialty (MOS)

a. In determining an MOS the general principle followed throughout is that duty assignments which basically involve the same kind of training, experience, techniques, abilities, and the same relative degree of physical capacity on the part of a soldier are classified together under a broad MOS. A duty assignment which is so specialized as to prevent grouping is recognized as an individual MOS. Examples, the job description of a Clerk-Typist (SSN 405) represents a broad classification and such duty assignments as Company Clerk, Typist, and Chaplain's Assistant fall within the area of skills which the MOS of Clerk-Typist represents. However, the job description of an Orthopedic Mechanic (SSN 366) represents a specialized duty assignment not susceptible to grouping and is an MOS in itself.

b. An MOS, therefore, is the term used to identify an Army job which comprises one or more related  duties and responsibilities normally requiring special knowledge and skills acquired through civilian training and experience supplemented by military training and experience, or military training and experience only.

c. The specification serial number (SSN) Is a numerical code assigned to an MOS for control, reporting, and requisitioning purposes.

Relationship of an MOS to Tables of Organization

Tables of Organization and Equipment and other Tables of Distribution may list any of the duty titles common to an MOS. Example, such duty assignments as Company Clerk, Typist, and Chaplain's Assistant can be performed by one qualified in the MOS of Clerk-Typist (SSN 405). Any or all of the above titles may appear in Tables of Organization. In each case, however, the SSN listed would be 405 since this is the numerical code which controls the authorized duty titles representing assignments which fall within the area of skills represented by the MOS of Clerk-Typist.

Relationship of a Military Occupational Specialty to the Arms and Services

a. In many cases the same MOS is required by more than one arm or service and it is customary for the arms and services involved to train and develop the required specialist, through school or unit training or both, usually for assignment within their respective organizations. The same training, techniques, and abilities and the same kind of work are required of the specialist, basically, regardless of the arm or service in which he is developed. However, because of differences in equipment, tactics, operations, physical capacities, etc., which exist in the various arms and services, it is indicated that an MOS should always be associated with the arm or service which developed it. In other words, the identity of the arm or service which develops an MOS is an integral part of that MOS and should be recognized as such. 

b. The above factors should be considered in all placement and replacement matters. For example, a Field Artillery trained Tank Mechanic, Minor Maintenance (SSN 660) should be assigned to a Field Artillery unit whereas an Armored Command trained Tank Mechanic, Minor Maintenance should be assigned to an Armored unit. However, where exigencies of the situation make this impracticable every attempt will be made to assign specialists to closely allied assignments in the order of their relationship to one another. Example, where a Field Artillery trained Tank Mechanic, Minor Maintenance (SSN 660) is required and is not available, the same kind of specialist who is either Tank Destroyer or Armored Command trained should be assigned because the same kind of work is required of these specialists, basically. The differences which exist as to type of equipment, tactics, etc., of an organization can be absorbed by the specialist. 

Determination of Soldier's Military Occupational Specialty

a. An MOS will be assigned an Enlisted Man only as follows:

  1. Through the successful completion of a course of training at a training center or service school, if it has been determined by proper authority that the course qualifies a graduate in a specialty. Determination by proper authority shall include clearance of military training programs with The Adjutant General's office (Classification and Replacement Branch) for determination of the appropriate MOS to be assigned to graduates of various courses.
  2. Through satisfactory performance of the duties and responsibilities of a military occupational specialty in a unit or installation for a period of 60 days.
  3. Through civilian experience, when of such nature as to be a practical counterpart of an MOS and when proficiency has been demonstrated to the satisfaction of his Commanding Officer.

b. Any solider not qualifying in an MSO in accordance with the above shall be classified as Basic (SSN 521) until such time as he qualifies for an appropriate MOS.

Qualification in an MOS

Accurate classification of each soldier in an appropriate MOS is of utmost importance. No soldier should be classified in an MOS unless he is able to perform satisfactorily the duties and responsibilities required by the job in accordance with the standards set out below and qualification in an MOS will be accomplished as follows:

a. "Skilled" if the Enlisted Man has demonstrated that, given the tools and equipment of his occupation he can perform all of his duties under sustained field, combat, or operating conditions without supervision beyond that inherent in the job itself.

b. "Semiskilled," if he can perform his duties under similar conditions but requires supervision.

c. "Potential" if he has sufficient familiarity with his tools and equipment and has such aptitudes and physical qualities as clearly warrants the assumption that he will become qualified as semiskilled or skilled with additional training and experience. Such men should be able to perform the various elements of the job under close supervision. 

Use of Alternate or Common Job Titles

The proper construction and development of Tables of Organization, common usage in the field, the type of training and experience available to the solider in the field, and tradition of an arm or service may indicate a title other than the official or main title of an MOS. Provision for such variation in title is arranged for as follows:

a. Wherever an MOS represents that type of specialty which qualifies a specialist to perform one or more duties and responsibilities falling within the area of skills represented by the MOS, job titles alternate to the main title are shown to indicate the most probable duties to which a specialist may be assigned. Examples of this are the use of such titles as Company Clerk, Battery Clerk, Headquarters Clerk, Chaplain's Assistant, or Typist with the MOS of Clerk-Typist (SSN 405), and in an Antitank unit, Cannoneer, Gunner, Driver, Radio Tender, or Antitank NCO with the MOS of Antitank Gun Crewman (SSN 610).

b. The general principle followed in considering common titles which are used throughout the Army to indicate the supervisory nature of the duty assignment has been to determine whether or not a soldier on a supervisory level is responsible for the supervision of a composite group of specialists on the operational level.

  1. In those cases where a soldier on a supervisory level requires no more basic knowledge than that of his military occupational specialty, plus his established leadership and other personal qualifications, his supervisory status is established by the enlisted grade to which he is promoted. His MOS remains the same.
    Example: An Antitank Gun Crewman (SSN 610) who, because of evidenced leadership and other personal supervisory qualifications, is promoted to the position of Antitank Noncommissioned Officer. In this case, the MOS Antitank Gun Crewman (SSN 610) is not changed excepting that the alternate title of Antitank NCO (SSN 610) should be used and accordingly posted in the item, "Record of Current Service" in the "Principal Duty" column of the Soldier's Qualification Card, W.D., A.G.O. Form No. 20. The enlisted grade to which the solider is promoted in this case establishes the supervisory nature of his assignment.
  2. In those cases where a soldier on a supervisory level is responsible for supervising a composite group of specialties on the operational level and who, in order properly to supervise the group, must have a thorough knowledge of the various kinds of military occupational specialists over which he has supervision, the enlisted grade to which he is promoted is not considered an adequate classification. By virtue of the knowledge the soldier develops of more than one MOS he automatically acquires a new MOS in this type of case.
    Example: The MOS of Administrative NCO (SSN 502) represents the kind of supervisory specialist who must be thoroughly familiar with more than one MOS on the operational level and such a specialist does not logically develop from only one MOS as in the case of the Antitank NCO.

c. Other common titles which are used throughout the Army to indicate the supervisory nature of the duty assignment may also be used as alternate titles. Examples of this are Sergeant Major, First Sergeant, Platoon Sergeant, Chief of Section, Section Leader, and Squad Leader. However, the SSN used in each case will be that SSN which represents the MOS of the Sergeant Major, First Sergeant, Platoon Sergeant, etc.
Examples: A Platoon Sergeant of a Rifle Company should be shown as Platoon Sergeant (SSN 745), if he is assigned to a Rifle Platoon or 1812 if assigned to an Infantry Platoon employing 60-mm mortars and light machine guns; a Platoon Sergeant of an Antitank Company should be shown as Platoon Sergeant (SSN 610); a First Sergeant whose duties require that he be an administrative specialist should be shown as First Sergeant (SSN 502); and a First Sergeant whose duties require a tactical specialist should be shown with the SSN covering his tactical specialty. For example, the First Sergeant of an Infantry Rifle Company should be shown as First Sergeant (SSN 1812). The First Sergeant of a Tank Destroyer Company (Firing) should be shown as First Sergeant (SSN 610).

To search or browse our database, simply navigate to the "MOS Code Database" link in the "Resources" menu at the top of the page, or click here.

Ben is also hard at work transcribing the MOS codes for Commissioned and Warrant Officers, so watch this space for more updates in the near future!

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