The military use of children takes three distinct forms: children can take direct part in hostilities (child soldiers); they can be used in support roles such as porters, spies, messengers, lookouts; or they can be used for political advantage [either] as human shields and/or in propaganda.
Throughout history and in many cultures, children have been extensively involved in military campaigns even when such practices were against cultural morals. In World War I, in Great Britain 250,000 boys under 18 managed to join the army. In World War II, child soldiers fought throughout Europe, in the Warsaw Uprising, in the Jewish resistance, and in the Soviet Army. Since the 1970s, a number of international conventions have come into effect that try to limit the participation of children in armed conflicts, nevertheless the Coalition to Stop the Use of Child Soldiers reports that the use of children in military forces, and the active participation of children in armed conflicts is widespread.
According to Wessels (1997), "The use of children in armed conflict is global in scope—a far greater problem than suggested by the scant attention it has received. Child soldiers are found from Central America to the Great Lakes region of Central Africa, and from Belfast in the north to Angola in the south" (p. 2). Children are easy targets to recruit for military purposes because of their vulnerability to influence. Many are seized and recruited by force whereas others join to escape their reality and circumstances.
Source : Wikipedia