In the early 1990s, a new threat to global security and human welfare caught the attention of political analysts and policymakers around the world, a threat that few observers had anticipated: pervasive and pernicious internal violence. They were right to be concerned. Civil wars (which take place primarily within the borders of a single state and among belligerents who normally reside in that state) accounted for 94 percent of all armed conflicts fought in the 1990s. From Africa to Central Asia, internecine violence and collapsing states became an unfortunate but familiar feature of the post–Cold War political landscape.

The nature of the threat posed by these conflicts was both humanitarian and strategic. From a humanitarian standpoint, this violence inflicted appalling losses on civilian noncombatants. At the beginning of the twentieth century, approximately 90 percent of war victims were soldiers; during the 1990s, by contrast, an estimated 90 percent of those killed in armed conflicts were civilians. Attacks and atrocities against noncombatants became widely employed as deliberate strategies of warfare – including such tactics as systematic rape, mass executions, ethnic cleansing, and even genocide – prompting some commentators to lament the revival of “premodern” forms of fighting that dispensed with customary constraints on the waging of war. Internal conflicts were also the principal source of mass refugee movements in the 1990s, which often gave rise to further humanitarian emergencies.