In the last several decades, we are witnessing cardinal changes in the nature of war. The flexibility in distinguishing between combatants and non-combatants was and is still necessary, especially in cases where civilians participate in hostilities without being awarded the status of combatant.
Throughout the history of war, there had always been civilian participation. For example, during a siege of city, everyone — combatants as well as civilians — took a part in the defense of the city, directly or indirectly. The phenomenon of civilian participation in war is as old as war itself, but only now, in the twenty-first century, humanity found itself facing the problem of its definition. The understanding of this requires research of the changes in causes and conditions for civilian participation: why civilians decide to participate in a war and what enables this participation.