This article discusses the contribution made by the jurisprudence of the Yugoslavia Tribunal to the articulation of the body of international humanitarian law that applies to all armed conflicts, regardless of whether they are international or internal. The Tadić Jurisdiction Decision rendered by the Appeals Chamber in 1995 set the stage for a substantial “rapprochement” of the regulatory content of war crimes committed in international and internal armed conflict, using Common Article 3 of the Geneva Conventions as the main vehicle. The first judgements have contributed greatly to the expansion of the body of “Geneva law” applicable to all armed conflicts. More recently, the Tribunal has started to examine cases of armed conflicts per se, in which perpetrators have been charged with violation of the “Hague law”, i.e., the law relating to the conduct of hostilities. The end result of this development will be elaboration of a common core of Geneva law and Hague law applicable to all armed conflicts that have reached the threshold of Common Article 3 of the Geneva Conventions.