Despite a considerable amount of ethnographic research into the phenomena of blood revenge and blood feud, little is known about the role of blood revenge in political violence, armed conflict, and irregular war. Yet blood revenge—widespread among many conflict-affected societies of the Middle East, North Africa, and beyond—is not confined to the realm of communal infighting, as previous research has presumed. An empirical analysis of Russia's two counterinsurgency campaigns in Chechnya suggests that the practice of blood revenge has functioned as an important mechanism in encouraging violent mobilization in the local population against the Russian troops and their Chechen proxies. The need to exact blood revenge has taken precedence over an individual's political views, or lack thereof. Triggered by the loss of a relative or humiliation, many apolitical Chechens who initially sought to avoid involvement in the hostilities or who had been skeptical of the insurgency mobilized to exact blood revenge to restore their individual and clan honor. Blood revenge functions as an effective, yet heavily underexplored, grievance-based mechanism encouraging violent mobilization in irregular wars.