This edition focuses on legal classification of armed conflict, which is critical in determining the obligations that arise for parties to a conflict. Qualifying a situation as an armed conflict to which international humanitarian law applies is an essential but delicate matter, considered to be the Achilles' heel of this legal regime. As conflicts increasingly involve non-state entities and have transnational dimensions, they also challenge the distinction between international and non-international armed conflicts. The current edition considers whether and how today's warfare fits into traditional legal categories, in order to determine which law protects the victims of these situations.