Children in the military are children (defined by the Convention on the Rights of the Child as persons under the age of 18) who are associated with military organisations, such as state armed forces and non-state armed groups. Throughout history and in many cultures, children have been involved in military campaigns. For example, thousands of children participated on all sides of the First World War and the Second World War.Norman Davies, Rising '44: The Battle for Warsaw, Pan Books 2004 p.603 Children may be trained and used for combat, assigned to support roles such as porters or messengers, or used for tactical advantage as human shields or for political advantage in propaganda.

Children are easy targets for military recruitment due to their greater susceptibility to influence compared to adults. Some children are recruited by force while others choose to join up, often to escape poverty or because they expect military life to offer a rite of passage to maturity.

Pre-20th century

Throughout history and in many cultures, children have been extensively involved in military campaigns.

The earliest mentions of minors being involved in wars come from antiquity. It was customary for youths in the Mediterranean basin to serve as aides, charioteers and armour bearers to adult warriors. Examples of this practice can be found in the Bible, such as David's service to King Saul, in Hittite and ancient Egyptian art, and in ancient Greek mythology (such as the story of Hercules and Hylas), philosophy and literature. In a practice dating back to antiquity, children were routinely taken on a campaign, together with the rest of a military man's family, as part of the baggage.

In ancient Egypt, boys under the teenage years would serve as errand-boys in the military. A depiction from Eighteenth Dynasty of Egypt shows young naked boys running errands for the military general. Other Ancient Egypt texts written by viziers describe that boys were active the military from very young age, and were active in the infantry upon entering teenage years.

The Roman Empire made use of youths in war, though it was understood that it was unwise and cruel to use children in war, and Plutarch implies that regulations required youths to be at least sixteen years of age. Despite this, several Roman legionaries were known to have enlisted children aged 14 in the Imperial Roman army, such as Quintus Postunius Solus who completed 21 years of service in Legio XX Valeria Victrix, and Caecilius Donatus who served 26 years in the Legio XX and died shortly before his honourable discharge.

In medieval Europe young boys from about twelve years of age were used as military aides ("squires"), though in theory, their role in actual combat was limited. The so-called Children's Crusade in 1212 recruited thousands of children as untrained soldiers under the assumption that divine power would enable them to conquer the enemy, although none of the children entered combat. According to the legend, they were instead sold into slavery. While most scholars no longer believe that the Children's Crusade consisted solely, or even mostly, of children, it nonetheless exemplifies an era in which entire families took part in a war effort.

In 1205 John, King of England prepared for the mobilisation of all males over the age of 12 and Sir John of Bromwich claimed he was a year younger in 1342 when he went to war for the first time. John of Gaunt, however, was considered too young to bear arms at the age of 10, although he was present at the Battle of Winchelsea. Weapons made for children dating from the period have survived.

Young boys often took part in battles during early modern warfare. When Napoleon was faced with invasion by a massive Allied force in 1814 he conscripted many teenagers for his armies. Orphans of the Imperial Guard fought in the Netherlands with Marshal MacDonald and were between the ages of 14 and 17.Michael Leggiere, The Fall of Napoleon: The Allied Invasion of France 1813–1814, pg.99–100 Many of the conscripts who reported to the ranks in 1814 were referred to as Marie Louises after the Empress Marie Louise of France; they were also known as "The Infants of the Emperor". These soldiers were in their mid-teens.Stephen Pope, Dictionary of the Napoleonic Wars, p. 318 One of their more visible roles was as the ubiquitous "drummer boy".

During the age of sail, young boys formed part of the crew of British Royal Navy ships and were responsible for many essential tasks including bringing powder and shot from the ship's magazine to the gun crews. These children were called "powder monkeys".

During the American Civil War a young boy, Bugler John Cook, served in the US Army at the age of 15 and received the Medal of Honor for his acts during the Battle of Antietam, the bloodiest day in American history.Slinger, P. W. Children at War. New York: Pantheon Books, 2005. Several other minors, including 11-year-old Willie Johnston, have also received the Medal of Honor.

By a law signed by Nicholas I of Russia in 1827 a disproportionate number of Jewish boys, known as the cantonists, were forced into military training establishments to serve in the army. The 25-year conscription term officially commenced at the age of 18, but boys as young as eight were routinely taken to fulfil the quota.

In the final stages of the Paraguayan War, children fought in the Battle of Acosta Ñu against the Allied forces of Brazil, Argentina and Uruguay. The day is commemorated as a national holiday in Paraguay.

During the Boshin War, the pro-shōgun Aizu Domain formed the , which was made up of the 16- to 17-year-old sons of Aizu samurai. During the Battle of Bonari Pass and the Battle of Aizu, they fought the Satcho forces who supported the Imperial cause. A detached unit of Byakkotai was cut off from the rest of the unit and retreated to Iimori Hill, which overlooked Aizu-Wakamatsu Castle. From there, they saw what they thought was the castle on fire. 20 of the detached unit committed seppuku while one was unsuccessful. He was saved by a local peasant.

World War I

The youngest known soldier of World War I was Momčilo Gavrić, who joined the 6th Artillery Division of the Serbian Army at the age of 8, after Austro-Hungarian troops in August 1914 killed his parents, grandmother, and seven of his siblings.Momčilo Gavrić – najmlađi vojnik Prvog svetskog rata ("Večernje novosti", 31 August 2013)

In the West, boys as young as 12 were caught up in the overwhelming tide of patriotism and in huge numbers enlisted for active service. Others enlisted to avoid harsh and dreary lives. Typically many were able to pass themselves off as older men, such as George Thomas Paget, who at 17 joined a Bantam battalion in the Welsh Regiment. In the Gallipoli campaign, otherwise known as "Çanakkale", children as young as 15 fought in the trenches. 120 children fought in the "15'liler" or "The 15s" company, with no known survivors.

Turkish War of Independence During the Turkish War of Independence, Turks kidnapped unwilling young men under the guise of "conscription" and used them as child soldiers, sending them to the front of the Greco-Turkish War.

Turkish general Kazim Karabekir established the "Army of Robust Children" (Gürbüzler Ordusu), kidnapping approximately six thousand poor and orphaned children, mostly Armenian or Kurdish, and dressing them like soldiers and subjecting them to military training.

In 1921, Turkish authorities made false birth certificates declaring Greek orphans to be older than they actually were. In this way, teenage boys were conscripted into labour battalions, where they were used as slave child soldiers and many of them died.

Spanish Civil War

Many child soldiers fought in the Spanish Civil War:

World War II

In World War II, children under the age of 18 were widely used by all sides in formal and informal military roles. Children were readily indoctrinated into the prevailing ideology of the warring parties, quickly trained, and often sent to the front line; many were wounded or killed. The lack of a legal definition of a child, combined with the absence of a system for verifying the ages of prospective child recruits, contributed to the extensive use of children in the war.

After World War II: Historical examples by region

Americas

El Salvador

During the civil war between 1980 and 1992 the Salvadoran military and the main opposition group, the Frente Farabundo Martí de Liberación National (FMLN), recruited children extensively. The recruitment was frequently carried out by force and focused on economically suppressed regions. A fifth of the army's personnel were aged under 18, as were a quarter of the FMLN. In a group of 278 former FMLN child soldiers interviewed for a study, the average age of recruitment was 10 years. The large majority of child recruits on both sides were living in poverty, and had been largely deprived of formal education. Many children who were not recruited by force joined of their own volition, mainly either to improve their circumstances or because they believed in the cause.

Far overshadowing the FMLN, the Salvadoran government's military forces relied on 48,000 recruits under the age of 18, roughly 80% of the entire army.

After the civil war came to a close, rehabilitation and reintegration programmes for children mostly failed; the majority of FMLN children were not involved in them, and the large majority of those who were dropped out of them. A decade after the peace accord former child soldiers were still experiencing nightmares, depression, anxiety, and related signs of psychiatric trauma.

Today, the Salvadoran military no longer sends children to war, but it still recruits and trains them from the age of 16.

Southwest Africa

Burundi Children were kidnapped and used extensively during the civil war of 1993–2005. In 2004 hundreds of child soldiers were in the Forces Nationales pour la Libération (FNL), an armed rebel, Hutu group., . Children between the ages of 10 and 16 were also conscripted by the Burundese military.

After the Arusha peace accord of 2001 and the Pretoria agreement of 2003 eventually brought the conflict to an end in 2005, the new constitution committed to not using children in direct combat. The parties to the conflict no longer recruited children in large numbers, but many remained active in the FNL, which had denounced the peace accord.

By 2006, a reintegration programme organised by UNICEF had led to the release of 3,000 children from the military and armed groups. According to Child Soldiers International:

, Burundi no longer appears on the UN list of countries where children are used in hostilities.

Chad Between 2007 and 2012, children were used extensively by the Chadian military as participants in armed conflict. They were also integrated into various rebel forces, including the United Front for Democratic Change (Front Uni pour le Changement, FUC), local self-defence forces known as Tora Boro militias, and two Sudanese rebel movements operating in Chad: the Justice and Equality Movement (JEM) and the G-19 faction of the Sudanese Liberation Army (SLA). After the government signed an action plan with the United Nations, children were released from service and were no longer recruited. By 2014, Chad had been removed from the UN list of countries that use child soldiers in war.

Côte d'Ivoire