The existence of an armed conflict is one of two international law doctrines (along with self-defense) that the United States has used to justify its use of lethal force in South Asia and the Middle East over the past twelve years. According to international humanitarian law (IHL), there are two types of armed conflict: international armed conflict (between two or more states) and non-international armed conflict (between a state and a non-governmental armed group, or between two or more such groups). When either conflict exists, the parties are legally permitted to use lethal force against opponent combatants. International armed conflicts have historically been easy to identify—violent engagements between states’ official armed forces—but have also grown rare. On the other hand, modern warfare is often marked by the presence of a violent non-state entity that can be difficult to even identify. To classify a non-international armed conflict, IHL sets forth certain conditions that must be met. One, there must be an identifiable, organized non-state armed group that engages in collective, anti-government violence. Two, that violence must meet a minimum threshold of intensity and duration (either protracted violence, or a isolated event of high intensity). Third, the conflict is contained geographically to the territory of the involved state and its opposition group, or the conflict is transnational (though still limited) in scope. However, one can easily see how these conditional requirements could be subject to debate—both theoretically and in the wake of actual violence—and present legal and ethical challenges over the use of lethal force.
We have broken our discussion of armed conflict and lethal force into three sub-topics that illustrate the difficulties of classifying conflicts and violence in modern warfare and explore the potential implications for the legal use of force. First, we look at the concept of “actual combat” and the importance of determining what qualifies as combat activity and what does not. In our second section, we consider how armed conflict is geographically constrained (or not) in the era of the “global war on terror.” Third, we ask if and when such a war can end.