Military recruitment
Demographics: 

Gender: Across the world, a large majority of recruits to state armed forces and non-state armed groups 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 US, and 27% in South Africa.
While many states do not recruit women for ground close combat roles (i.e. roles which would require them to kill an opponent at close quarters), several have lifted this ban in recent years, including larger Western military powers such as France, the UK, and US.
Compared with male personnel and female civilians, female personnel face substantially higher risks of sexual harassment and sexual violence, according to British, Canadian, and US research.
Some states, including the UK, US and Canada have begun to recognise a right of transgender people to serve openly in their armed forces, although this development has met with political and cultural resistance.

Age group: State armed forces set minimum and maximum ages for recruitment. In practice, most military recruits are young adults; for example, in 2013 the average age of a United States Army soldier beginning initial training was 20.7 years.

Child recruitment: Under the Convention on the Rights of the Child, a child means a person aged under 18.
The minimum age at which children may be recruited or conscripted under the Rome Statute of the International Criminal Court is 15. States which have ratified the Optional Protocol to the Convention on the Rights of the Child on the Involvement of Children in Armed Conflict (OPAC) may not conscript children at all, but may enlist children aged 16 or above provided that they are not used to participate directly in hostilities.
Historically, the use of children for military purposes has been widespread—see Children in the military—but has been in decline in the 21st century. According to Child Soldiers International, as of 2017 approximately two-thirds of states worldwide had committed to restrict military recruitment to adults from age 18, and at least 60 non-state armed groups had signed agreements to stop or reduce the use of children for military purposes. The organization reported that the so-called Straight 18 standard – the restriction of all military employment to adults – had been emerging as a global norm since 2001.
However, Child Soldiers International also reported in 2018 that at least 46 states were recruiting personnel below the age of 18. Most of these states were recruiting from age 17, including Australia, China, France, Germany, Saudi Arabia and the United States (US); approximately 20 were recruiting from age 16, including Brazil, Canada, and the United Kingdom (UK).
Most states which recruit children under the age of 18 have undertaken not to deploy them routinely on military operations, having ratified the OPAC treaty. According to the Secretary-General of the United Nations (UNSG), in 2016 14 states were still recruiting and using children in active armed conflicts: Afghanistan, Central African Republic, Colombia, Democratic Republic of Congo, Iraq, Mali, Myanmar, Nigeria, Philippines, Somalia, South Sudan, Sudan, Syria and Yemen.
The UNSG also reported that non-state armed groups were recruiting and using children in armed conflict in India, Pakistan,  Palestine, Libya, Philippines and Thailand.
Cross-cultural studies suggest that, in general, children and young people are drawn to military employment for similar reasons: war, economic motivation, education, family and friends, politics, and identity and psychosocial factors.

Socio-economic background: The hope of escaping socio-economic deprivation is one of the main factors attracting young people to military employment. (Thus the obsolete English-language term "bezonian" may mean "raw recruit" or "pauper".) 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". However, a 2020 study suggests that the socio-economic status of U.S. Armed Forces personnel is at parity with or slightly higher than the civilian population and that the most disadvantaged socio-economic groups are less likely to meet the requirements of the modern U.S. military. A study found that technological, tactical, operational and doctrinal changes have led to a change in the demand for personnel. As an indication of the socio-economic background of British Army personnel, as of 2015 three-quarters of its youngest recruits had the literacy skills normally expected of an 11-year-old or younger, and 7% had a reading age of 5–7. The British Army's recruitment drive in 2017 targeted working-class families with an average annual income of £10,000.
Recruitment for officers typically draws on upwardly-mobile young adults from age 18, and recruiters for these roles focus their resources on high-achieving schools and universities. (Canada is an exception, recruiting high-achieving children from age 16 for officer training.)

Outreach and marketing: 

Early years: The process of attracting children and young people to military employment begins in their early years. In Germany, Israel, Poland, the UK, the US, and elsewhere, the armed forces visit schools frequently, including primary schools, to encourage children to enlist once they become old enough to do so. For example, a poster used by the German armed forces in schools reads: "After school you have the world at your feet, make it safer." ["Nach der Schule liegt dir die Welt zu Füßen, mach sie sicherer."] In the US, recruiters have right of access to all schools and to the contact details of students, and are encouraged to embed themselves into the school community. A former head of recruitment for the British Army, Colonel (latterly Brigadier) David Allfrey, explained the British approach in 2007:Our new model is about raising awareness, and that takes a ten-year span. It starts with a seven-year-old boy seeing a parachutist at an air show and thinking, 'That looks great.' From then the army is trying to build interest by drip, drip, drip.

Popular culture: Recruiters use action films and videogames to promote military employment. Scenes from Hollywood blockbusters (including Behind Enemy Lines and X-Men: First Class) have been spliced into military advertising in the US, for example. In the US and elsewhere, the armed forces commission bespoke videogames to present military life to children and have created the U.S. Army Esports initiative as an outreach program using esports.

Military schools and youth organisations: Many states operate military schools, cadet forces, and other military youth organisations. For example, Russia operates a system of military schools for children from age 10, where combat skills and weapons training are taught as part of the curriculum. The UK is one of many states that subsidise participation in cadet forces, where children from age 12 play out a stylised representation of military employment. The United States offers Junior Reserve Officers' Training Corps to high school students as an extracurricular activity.

Advertising: Armed forces commission recruitment advertising across a wide range of media, including television, radio, cinema, online including social media, the press, billboards, brochures and leaflets, Employment websites and through merchandising.

Public realm: Recruiters use civic space to promote their military organisation. Among the methods used are recruitment stalls in public spaces, air shows; military amusement parks, such as Patriot Park in Russia; national days, such as the Belgian national day and military parade; and annual armed forces days.

Messaging: Recruitment marketing seeks to appeal to potential recruits in the following ways:

Traditionally masculine associations. Historically and today, recruitment materials frequently associate military life with that of a traditionally masculine warrior, which is officially encouraged as a martial ideal. For example, Cold War US Army slogans included "Join the army, Be a man" and "The army will make a man out of you"; in 2007 a new slogan was introduced: "There's strong. Then there's army strong". Similarly, recruiters describe the Israeli infantryman as "discovering all your strengths"; and the British is "harder, faster, fitter, stronger".
Teamwork and belonging. Some armed forces appeal to potential recruits with the promise of teamwork and camaraderie. An example is the British Army, which introduced the slogan "This is belonging" in 2017.
Patriotic service. Some armed forces present military life as a patriotic service. For example, the slogan for the German Bundeswehr is "We. Serve. Germany." ["Wir. Dienen. Deutschland."], and an advertisement for the Israeli Defense Forces encourages potential recruits to "Above all, fight [kravi] for your country, because there is no place better than Israel."
Challenge and adventure. Military life is promised to be exciting, including world travel and adventurous training. In 2015, the British Army presentation to schools included prominent images of scuba diving and snowboarding, for example.
Education and skills. The armed forces are often presented as a means to learn new skills. For example, the Swedish armed forces encourage potential recruits with the promise of "education that leads to a job where you can make a difference".

Application process: Typically, candidates for military employment apply online or at a recruitment centre.
Many eligibility criteria normally apply, which may be related to age, nationality, height and weight (body mass index), medical history, psychiatric history, illicit drug use, criminal record, academic results, proof of identity, satisfactory references, and whether any tattoos are visible.