A possibility for them. A lot of monstrous numbers.

UNICEF
The campaign Children, Not Soldiers - Children Soldiers in the World
The UN Secretary-General’s report on children and armed conflict includes a “list of shame”, which identifies armed forces and groups that recruit and use children. When parties are added to the list, they are put under increased scrutiny and may be subject to punitive measures.
The 2016 list includes parties which recruit and use children in these conflicts:

• Afghanistan
• Central African Republic
• Democratic Republic of Congo
• Iraq
• Mali
• Myanmar
• Somalia
• South Sudan
• Sudan
• Syria
• Yemen
• Colombia
• Nigeria
• Philippines

CHILD SOLDIERS
What is a child soldier? Declaration of the Rights of the Child - ARTICLE 9
A child associated with an armed force or armed group refers to any person below 18 years of age who is, or who has been, recruited or used by an armed force or armed group in any capacity, including but not limited to children, boys and girls, used as fighters, cooks, porters, spies or for sexual purposes.
In many conflicts children take direct part in combat. However, their role is not limited to fighting. Many girls and boys start out in support functions that also entail great risk and hardship.
One of the common tasks assigned to children is to serve as porters , often carrying heavy loads, including ammunition or injured soldiers . Some children act as lookouts, messengers, cooks or other routine duties.
Girls are particularly vulnerable. They are often forced to serve as sexual slaves . Moreover, the use of children for acts of terror, including as suicide bombers , has emerged as a phenomenon of modern warfare.
Regardless of how children are recruited and of their roles, child soldiers are victims , whose participation in conflict bears serious implications for their physical and emotional well-being. They are commonly subject to abuse and most of them witness death, killing, and sexual violence. Many are forced to perpetrate these atrocities and some suffer serious long-term psychological consequences . The reintegration of these children into civilian life is a complex process.

BUT, WHAT ARE THE PROBLEMS FOR CHILD SOLDIERS? - Child soldiers: two words that shouldn't be together.
Compared with the physical impacts, the psychological ones can be seen as a more severe problem which calls for professional psychologists which are scarce.
Many child soldiers are kidnapped on their way to school or home, they often have memories of violent events like killing their peers or family members, which result to psychological damage. Post-traumatic stress disorder (PTSD), depression, anxiety, substance abuse, suicidal behavior, social withdrawal, low self-esteem, loss of trust, excessive guilt, hostility and aggression can be counted among these mental disorders The child shall be protected against all forms of neglect, cruelty and exploitation. He shall not be the subject of traffic, in any form.
The child shall not be admitted to employment before an appropriate minimum age; he shall in no case becaused or permitted to engage in any occupation or employment which would prejudice his health or education, or interfere with his physical, mental or moral development.
The campaign Children, Not Soldiers, aims to galvanize support to end and prevent the recruitment and use of children by national security forces in conflict. Since the campaign launch in March 2014:

• The campaign received broad support from Member States, UN, NGO partners, regional organizations and the general public.
• The government of Afghanistan criminalized the recruitment of children.
• The President of the Democratic Republic of the Congo (DRC) named a Presidential Advisor to address sexual violence and child recruitment.
• Somalia ratified the Convention on the Rights of the Child in September 2015.
• Sudan signed an action plan with the United Nations to end and prevent the recruitment and use of children in the country's security forces.
• Yemen signed an Action Plan with the UN in May 2014.