There is a term of MOS or Military Occupation Specialty in the United States of Army. This is a system of categorization of work and subjects of the personnel that is related.

There is a Career Management Fields (CMF) that will mention about the career classifications of the Army groups. For example in the CMF of Artillery will contain about the MOS that mentioned about several points: specialist of fire support, member of canon team and member of system of the multiple launch rocket team. There are many classifications contains in the MOS of Army such as: air defense, military intelligence, military police, chemical corps, and many more. The personnel that join the Army will decide the MOS according to their interests at the moment they enroll in the military. If those applicants are still not sure about which career will they chose, there is a test called the Armed Forces Vocational Aptitude Battery that able to assist new member to guide for the interest. There will be a basic training which held in 14 weeks and afterward will be continued with the MOS training. The location of MOS training will be held in all over the country.