A civil war is defined as "a war between opposing groups of citizens of the same country." This type of warfare is rooted in the very origins of humanity and can be traced back to the dawn of organized states. A civil war is set in a different context than other wars. It is an internal conflict pitting "brother against brother." As such, it is often much more intense and costly than any form of warfare. Such internal armed conflicts, unlike those that cross political as well as geographic boundaries, frequently have been overlooked in the laws of war. It is only recently that the laws of war have been considered in the context of civil war.
Charles L. Nier III, The Yugoslavian Civil War: An Analysis of the Applicability of the Laws of War Governing Non-International Armed Conflicts in the Modern World, 10 Penn St. Int'l L. Rev. 303 (1992).