International criminal law (ICL) is a body of public international law designed to prohibit certain categories of conduct commonly viewed as serious atrocities and to make perpetrators of such conduct criminally accountable for their perpetration. The core crimes under international law are genocide, war crimes, crimes against humanity, and the crime of aggression.

A war of aggression, sometimes also war of conquest, is a military conflict waged without the justification of self-defense, usually for territorial gain and subjugation, in contrast with the concept of a just war.