International Humanitarian Law (IHL) applies in two very different types of situations: international armed conflicts and noninternational armed conflicts.
International armed conflict
IHL relating to international armed conflict applies “to all cases of declared war or of any other armed conflict which may arise between two or more of the High Contracting Parties, even if the state of war is not recognized by one of them.”The same set of provisions also applies “ to all cases of partial or total occupation of the territory of a High Contracting Party, even if the said occupation meets with no resistance”.
According to traditional doctrine the notion of international armed conflict was thus limited to armed contests between states. During the Diplomatic Conference which led to the adoption of the two Additional Protocols of 1977, this conception was challenged and it was finally recognized that “wars of national liberation”should also be considered international armed conflicts.
Non-international armed conflict
Traditionally non-international armed conflicts (or, to use an outdated terminology: civil wars) were considered purely internal matters for states, for which no international law provisions applied. This view was radically modified with the adoption of Article 3 common to the four Geneva Conventions of 1949. For the first time, the community of States agreed on a set of minimal guarantees to be respected during non-international armed conflicts. Broader explaination under Aditional Protocol II of 1977 “Shall apply to all armed conflicts not covered by Article 1 of Protocol I and which take place in the territory of a High Contracting Party between its armed forces and dissident armed forces or other organized armed groups which, under responsible command, exercise such control over a part of its territory as to enable them to carry out sustained and concerted military operations and to implement this Protocol.”