Children in the military
As such, the treaty does not ban the recruitment of children aged 16 or 17, although it allows states to bind themselves to a higher standard in law.

2000s–present: After the adoption of the Optional Protocol on the Involvement of Children in Armed Conflict, a campaign for global ratification made swift progress. As of 2018 OPAC had been ratified by 167 states. The campaign also successfully encouraged many states not to recruit children at all. In 2001 83 states only allowed adult enlistment. By 2016 this had increased to 126, which is 71 percent of countries with armed forces. Approximately 60 non-state armed groups have also entered agreements to stop or scale back their use of children, often brokered by the UN or the NGO Geneva Call.
Child Soldiers International reports that the success of the OPAC treaty, combined with the gradual decline in child recruitment by state armed forces, has led to a reduction of children in military organisations worldwide. As of 2018 the recruitment and use of children remains widespread. In particular, militant Islamist organisations such as ISIS and Boko Haram, as well as armed groups fighting them, have used children extensively. In addition, the three most populous states – China, India and the United States – still allow their armed forces to enlist children aged 16 or 17, as do five of the Group of Seven countries: Canada, France, Germany, the United Kingdom and the United States, again.

Events: Red Hand Day (also known as the International Day Against the Use of Child Soldiers) on 12 February is an annual commemoration day to draw public attention to the practice of using children as soldiers in wars and armed conflicts. The date reflects the entry into force of the Optional Protocol on the Involvement of Children in Armed Conflict.

Countering the militarisation of childhood: Many states which do not allow their armed forces to recruit children have continued to draw criticism for marketing military life to children through the education system, in civic spaces and in popular entertainment such as films and videogames. Some commentators have argued that this marketing to children is manipulative and part of a military recruitment process and should therefore be evaluated ethically as such. This principle has led some groups to campaign for relations between military organisations and young people to be regulated, on the grounds of children's rights and public health. Examples are the Countering the Militarization of Youth programme of War Resisters' International, the Stop Recruiting Kids campaign in the US, and the Military Out of Schools campaign in the UK. Similar concerns have been raised in Germany and Israel.

Rehabilitation and reintegration of child soldiers: Child Soldiers International defines reintegration as: "The process through which children formerly associated with armed forces/groups are supported to return to civilian life and play a valued role in their families and communities" Programs that aim to rehabilitate and reintegrate child soldiers, such as those sponsored by UNICEF, often emphasise three components: family reunification/community network, psychological support, and education/economic opportunity. These efforts take a minimum commitment of 3 to 5 years in order for programs to be successfully implemented. Generally, reintegration efforts seek to return children to a safe environment, to create a sense of forgiveness on the behalf of the child's family and community through religious and cultural ceremonies and rituals, and encourage the reunification of the child with his or her family.
Reintegration efforts can become challenging when the child in question has committed war crimes because in these cases stigma and resentment within the community can be exacerbated. In situations such as these, it is important that the child's needs are balanced with a sense of community justice. These situations should be addressed immediately because if not, many children face the threat of re-enlistment. There are also two areas of reintegration that warrant special consideration: female child soldiers and drug use among child soldiers. Child soldiers under the influence of drugs or who have contracted sexually transmitted diseases require additional programmes specific to their needs.

See also: 

General: History of children in the military
Children in emergencies and conflicts
Children's rights
Child slavery
Child labour
Stress in early childhood

Well-known cases of children used for military purposes: Grace Akallo, Ugandan
Loung Ung, Cambodian
Ishmael Beah, Sierra Leonean
Calvin Graham, American
Hagdobyeong, Korean
Himeyuri students, Japanese
Mohammad Hossein Fahmideh, Iranian
Omar Khadr, Canadian
Luftwaffenhelfer, German
Lwów Eaglets, Polish
Dominic Ongwen, Ugandan
Returned: Child Soldiers of Nepal's Maoist Army (documentary film)

Campaigns and campaigners to end the use of children in the military: Child Soldiers International
Els de Temmerman
Graça Machel
Romeo Dallaire
War Resisters International (Countering Militarization of Youth programme)
Red Hand Day

Related crimes against children: Trafficking of children

Related international law and standards: Convention on the Rights of the Child
Rome Statute of the International Criminal Court
Worst Forms of Child Labour Convention
International humanitarian law
United Nations Security Council Resolution 1998
Working Group on Children and Armed Conflict
Free Children from War conference, which established the Paris Principles

Documentary film: Kony 2012, documentary film
La vita non perde valore (Life does not lose its value), documentary film

Further reading: Vautravers, A. J. (2009). Why Child Soldiers are Such a Complex Issue. Refugee Survey Quarterly, 27(4), 96–107. doi:10.1093/rsq/hdp002
Humphreys, Jessica Dee (2015). Child Soldier: When Boys and Girls Are Used in War. Toronto: Kids Can Press ISBN 978-1-77138-126-0
International Centre for Counter-Terrorism (ICCT) & The Global Center on Cooperative Security (September 2017). "Correcting the Course: Juvenile Justice Principles for Children Convicted of Violent Extremism Offenses", ICCT & GCCS, 1–12. Correcting the Course: Advancing Juvenile Justice Principles for Children Convicted of Violent Extremist Offenses
Dr U C Jha (2018), "Child Soldiers – Practice, Law and Remedies". Vij Books India Pvt Ltd ISBN 9789386457523
Artur Bogner, Gabriele Rosenthal (2020): Child Soldiers in Context. Biographies, Familial and Collective Trajectories in Northern Uganda. Göttingen: University Press. Child Soldiers in Context

References: 

External links: 

Advocacy and campaigns: Human Rights Watch, "Child Soldiers"
UNICEF, "Child Soldiers"
War Child
Watchlist

Reference: Child soldiers worldwide: Child Soldiers International, historical reports:
Child Soldiers Global Report: 2001
Child Soldiers Global Report: 2004
Louder than words: 2012

Testimony and reportage: "Girl Soldiers – The cost of survival in Northern Uganda Archived 23 May 2012 at the Wayback Machine", womennewsnetwork.net.
"Invisible Children—The Tragedy in Uganda, Every Child Ministries", ecmafrica.org
"Children of Karamoja" (Uganda), forlife-worldwide.com
"Involvement of children in armed formations during the military conflict in Donbas" Archived 11 February 2017 at the Wayback Machine (Ukraine), jfp.org.ua
"Sex slavery awaits Ugandan schoolgirls", BBC News
"Ugandan army recruiting children", BBC News
"Criticism of British child soldier recruitment", BBC News
"Armies of girls caught up in conflict", The Guardian
"The Child Soldiers of Staten Island", Mother Jones

International institutions: International Committee of the Red Cross, "Children in war"
Special Representative of the UN Secretary General for Children and Armed Conflict
International Labour Organization, "Child labour and armed conflict"

Other: Podcast on child soldiers in the Middle East