They say the government can't function without a mountain of paperwork - the 0102 Manpower Officer (commonly referred to as an Adjutant, or "Adj" for short) is the Marine who helps smooth out that mountain so the rest of the Marines don't get tripped up by it. They are easily the most relied upon MOS, responsible for ensuring the function of a unit - without accurate personnel admin, the Marine Corps simply doesn't function. Commanders at all levels learn this lesson very quickly, making the 0102 a very valuable member of the team.

0102's serve as Battalion Adjutants, Division/Group/Wing Manpower Officers, and at myriad headquarters billets. They are responsible for ensuring the functionality and accuracy of all directives, manpower policies, disciplinary and legal actions, promotions, awards, leave and liberty, personnel administration, and associated collateral programs. They process every piece of personnel administration in a unit, direct policy for major subordinate commands (i.e. MarDiv, MLG, Wing). Nearly every commander at the Battalion level and up has an 0102 assigned to advise them on best practices regarding the aforementioned functional areas.

Manpower Officers plan, coordinate, execute and/or supervise the functions of administration (general administration, operational administration, manpower administration, and personnel administration) in their respective commands and organizations. Manpower Officers coordinate with MOS 0170 Personnel Officers for matters of Personnel Administration, for which the Installation Personnel Administration Center (IPAC) has primary cognizance. Manpower Officers serve as advisors to commanders for administrative matters. Manpower Officers are MAGTF officers, whom support operations with policies and programs affecting service members in areas other than training and logistics.

In addition to coordinating administration, Manpower Officers are responsible for working to maintain a battalion or squadron's Table of Organization (T/O) that drives the manning and staffing of a unit. They coordinate this with higher headquarters and Manpower Management (MM) division at HQ Marine Corps to get Marines assigned to the unit.

The Adjutant’s scope of responsibility varies by command but typically includes coordination and execution of administrative services by supporting Personnel Administration Centers, daily confirmation and certification of on-hand personnel, deployable strength reporting, military justice, mailroom operations, and casualty response operations. Adjutants will become familiar with Defense Travel System application, the approval and procurement process for government travel in support of official events and training, routine and special correspondence, maintenance of files and directives, personnel strength reporting, and processing individual military awards and decorations. The majority of Adjutants are entrusted with the collateral responsibility of Legal Officer, which is vital to maintaining good order and discipline in units. As the key advisor to the commander on all matters related to manpower, the Adjutant must possess interpersonal skills, be mature, and perceptive. Other desirable include discretion, empathy, and trust. Adjutants typically have three to 15 Marines under their supervision, several of whom are NCOs and SNCOs. This small number of personnel is responsible for supporting and enabling the Corps’ greatest resource, its Marines.