In order for IHL to apply to a situation of violence, that situation must constitute an armed conflict. As different sets of rules apply to international and non-international armed conflicts, it is also important to identify the nature of the conflict. The entirety of the four Geneva Conventions, as well as the rules of Additional Protocol I apply to international armed conflicts, while Article 3 Common to the four Geneva Conventions and Additional Protocol II apply to non-international armed conflicts.

Article 2 Common to the Geneva Conventions defines international armed conflicts as ‘all cases of declared war or of any other armed conflict which may arise between two or more of the High Contracting Parties.’ Therefore, all conflicts occurring between two States are international in character. Non-international armed conflicts are, under Article 3 Common to the Geneva Conventions, those conflicts that are ‘not of an international character’.

Therefore, the key distinction between the two types of conflicts appears to be the parties involved in the conflict. Hence, if the armed conflictis between two or more States, it will be classified as international, whereas if one of the parties is non-State in character, it will be classified as non-international. 

See Classification of persons; Armed conflict; Armed groups; International armed conflict; Non-international armed conflict;

 OUTLINE

Chapter 2, III. 1. Situations of application
Chapter 12, III. Different types of Non-international armed conflicts
Chapter 15, IV. 1. The ICRC and the legal qualification of a situation
Exercise on the Classification of Armed Conflicts

 CASES

 BIBLIOGRAPHIC RESOURCES

BARTELS Rogier, “Timelines, Borderlines and Conflicts: the Historical Evolution of the Legal Divide between International and Non-International Armed Conflicts”, in IRRC, Vol. 91, No. 873, March 2009, pp. 35-67   BYRON Christine, “Armed Conflicts: International or Non-International?”, in Journal of Conflict and Security Law, Vol. 6, No. 1, June 2011, pp. 63-90.   CARSWELL Andrew J., “Classifying the Conflict: a Soldier’s Dilemma”, in IRRC, Vol. 91, No. 873, March 2009, pp. 143-161   CRAWFORD Emily, “Blurring the Lines Between International and Non-International Armed Conflicts: The Evolution of Customary International Law Applicable in Internal Armed Conflicts”, in Australian International Law Journal, Vol. 15, 2008, pp. 29-54   DAHL Arne Willy & SANDBU Magnus, “The Threshold of Armed Conflict”, in Revue de droit militaire et de droit de la guerre, Vol. 3-4, No. 45, 2006, pp. 369-388   GRAY Christine, “Bosnia and Herzegovina: Civil War or Inter-State Conflict? Characterization and Consequences”, in BYIL, Vol. 67, 1996, pp. 155-197.   GREENWOOD Christopher, “Scope of Application of Humanitarian Law”, in FLECK Dieter (ed.), Handbook of Humanitarian Law, Oxford, OUP, 2nd ed., 2008, pp. 201-263.   KÜEFNER Stefanie, “The Threshold of Non-International Armed Conflict: the Tadic Formula and its First Criterion Intensity”, in Militair-Rechtelijk Tijdschrift, Vol. 102, Issue 6, 2009, pp. 301-311   KWAKWA Edward K., The International Law of Armed Conflict: Personal and Material Fields of Application, Dordrecht, Kluwer, 1992, 208 pp.   MERON Theodor, “Classification of Armed Conflict in the Former Yugoslavia, Nicaragua’s Fallout”, in AJIL, Vol. 92/2, 1998, pp. 236-242.   O’CONNELL Mary Ellen, Defining Armed Conflict”, in Journal of Conflict & Security Law, Vol. 13, No. 3, 2008, pp. 393-400   SASSÒLI Marco, “The Legal Qualification of the Conflicts in the former Yugoslavia: Double Standards or New Horizons for International Humanitarian Law?”, in WANG Tieya & YEE Sienho (eds), International Law in the Post-Cold War World: Essays in Memory of Li Haopei, Routledge, London, 2001, pp. 307-333   SCHINDLER Dietrich, “The Different Types of Armed Conflicts According to the Geneva Conventions and Protocols”, in Collected Courses, Vol. 163, 1979, pp. 119-163.   SIOTIS Jean, Le droit de la guerre et les conflits armés d’un caractère non international, Paris, LGDJ, 1958, 248 pp.   SIVAKUMARAN Sandesh, “Identifying an Armed Conflict not of an International Character”, in STAHN Carsten & SLUITER Göran (eds), The Emerging Practice of the International Criminal Court, Leiden, Boston, M. Nijhoff, 2009, pp. 363-380   THAHZIB-LIE Bahia & SWAAK-GOLDMAN Olivia, “Determining the Threshold for the Application of International Humanitarian Law”, in LIJNZAAD Liesbeth, VAN SAMBEEK Johanna & TAHZIB-LIE Bahia (eds), Making the Voice of Humanity Heard, Leiden/Boston, M. Nijhoff, 2004, pp. 239-253   VERHOEVEN Sten, “International and Non-International Armed Conflicts”, in Institute for International Law K.U. Leuven, Working Paper No. 107, 2007, 22 pp.   VITE Sylvain, “Typology of Armed Conflicts in International Humanitarian Law: Legal Concepts and Actual Situations”, in IRRC, Vol. 91, No. 873, March 2009, pp. 69-94