Military use of children takes three distinct forms: children can take direct part in hostilities as child soldiers, or they can be used in support roles such as porters, spies, messengers, look outs, and sexual slaves; or they can be used for political advantage either as human shields or in propaganda. Throughout history and in many cultures, children have been extensively involved in military campaigns even when such practices were supposedly against cultural morals. 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