Counterinsurgencies are especially lethal for civilians, as both parties to the conflict fight to control the population and gain intelligence on each other. In this context, the international community has increasingly stressed since the 1949 Fourth Geneva Convention, the need for all parties to reduce civilian casualties in accordance with the Law of Armed Conflict. However, the strategic implications of civilian casualties, which vary depending on whether insurgents or counterinsurgents are responsible, have remained to a large extent unexamined in terms of counterinsurgency theory. In Afghanistan, allied forces and the Taliban, to a much lesser extent, have made it a priority to reduce civilian casualties caused by their side, in order to avoid antagonizing the population. However, this focus ignores the fact that simply avoiding antagonizing the population is not the same as gaining its support. The lessons learned from the principles of civilian casualties derived from counterinsurgency provide ample ammunition for military and political leaders to extinguish an insurgency over the course of protracted warfare by following strategies to win the support of the population.