Military personnel or military service members are members of the state's armed forces. Their roles, pay, and obligations differ according to their military branch (army, navy, marines, coast guard, air force, and space force,), rank (officer, non-commissioned officer, or enlisted recruit), and their military task when deployed on operations and on exercise.
Those who serve in a typical large ground or land force are soldiers, this branch is the army. Those who serve in seagoing forces are seamen or sailors, and their branch is a navy or coast guard. Naval infantry or marines serve both on land and at sea, and their branch is the marine corps. In the 20th century, the development of powered flight aircraft prompted the development of air forces, serviced by airmen. The United States Space Force service members are known as guardians.
Designated leaders of military personnel are officers. These include commissioned officers, warrant officers and non-commissioned officers. For naval forces, non-commissioned officers are referred to as petty officers.
Military personnel may be conscripted (recruited by compulsion under the law) or recruited by attracting civilians to join the armed forces. Most personnel at the start of their military career are young adults. For example, in 2013 the average age of a United States Army soldier beginning initial training was 20.7 years.
Most personnel are male. The proportion of female personnel varies internationally; for example, it is approximately 3% in India, 10% in the UK, 13% in Sweden, 16% in the U.S., and 27% in South Africa. Many state armed forces that recruit women ban them from ground close-quarters combat roles.
Personnel who join as officers tend to be upwardly mobile young adults from age 18. Most enlisted personnel have a childhood background of relative socio-economic deprivation. For example, after the US suspended conscription in 1973, "the military disproportionately attracted African American men, men from lower-status socioeconomic backgrounds, men who had been in nonacademic high school programs, and men whose high school grades tended to be low".