ABSTRACT
The twentieth century saw more change in warfare than did the previous 3,000 years. One obvious change was the development of weapons of mass destruction. Early in the century, most casualties in a war were military personnel, but by the end of the period, most casualties were civilians. Less obvious has been the transition from interstate wars to intrastate wars, from conflicts between countries to conflicts within countries. In recent years, almost all wars have been civil wars between factions within a nation-state.
