International Law - crimes by or against the state are usually classified into the following
categories:

War crimes -  Acts of violence against civilian populations or prisoners of war by military
personnel in violation of the laws and customs of war, not justified by military necessity; Acts
involving weapons or military methods of unusual cruelty or devastation.  Violence is the nature
of warfare, though it is generally recognized that violence should be limited to military
personnel and military targets. Examples - American bombing of Dresden during WWII;
German V1 and V2 rocket attacks; American atomic bomb attacks on Japan; Iraq gassing of
Kurds.

Crime Against Peace - Acts based on the distinction between offensive and defensive warfare.
Offensive wars are illegal, but wars in defense of one’s country and sovereignty are legal.
Examples - Soviet invasion of Afghanistan; American invasion of Panama; Nazi invasion of
Poland; Iraq invasion of Kuwait.

Crime Against Humanity - Acts that violate concepts of natural law and natural rights of human
beings as human beings.    Examples - Serbian purge of Bosnia; Jewish holocaust of WWII;
Turkish genocide of Armenians in WWI; Iraq purge of Kurds; American internment of Japanese
during WWII;
 

see generally, L. Friedman “War Crimes,” in S. H. Kadish (ed)  Encyclopedia of Crime and
Justice, New York, Free Press, 1983, p. 1645.