Recognizing that many of today's conflicts are low-intensity, asymmetrical wars fought between disparate military forces, William C. Banks's collection debates nonstate armed groups and irregular forces (such as terrorist and insurgent groups, paramilitaries, child soldiers, civilians participating in hostilities, and private military firms) and their challenge to international humanitarian law. Banks and others believe gaps in the laws of war leave modern battlefields largely unregulated, and governing parties suffer without guidelines for responding to terrorism, transnational armed forces, and asymmetrical tactics, such as the targeting of civilians. These gaps also embolden weaker, nonstate combatants to exploit forbidden strategies and violate the laws of war. Attuned to the contested nature of post-9/11 security and policy, this collection juxtaposes diverse perspectives on existing laws and their application in contemporary conflict. They set forth a legal definition of new wars, describe the status of new actors, chart the evolution of the twenty-first-century battlefield, and balance humanitarian priorities with military necessity. Though they contest each other, these contributors ultimately reestablish the legitimacy of a long-standing legal corpus and rehumanize an environment in which the most vulnerable targets, civilian populations, are themselves becoming weapons against conventional power.