Between 1980 and 1992, the tiny Central American republic of El Salvador was engulfed in a brutal civil war. The Salvadoran armed forces, internal security forces such as the National Guard and National Police, and death squads allied with them killed tens of thousands of Salvadoran civilians in an effort to wipe out the guerrilla insurgency of the Farabundo Martí National Liberation Front (FMLN). Throughout the conflict, but most particularly in its early years, state forces committed grave and systematic abuses of human rights, including massacres, murders, disappearance, and torture. The FMLN carried out a smaller but nonetheless serious number of violations of international humanitarian law, including targeted assassinations of prominent public figures, kidnappings for ransom, and harming civilians in violation of the rule of proportionality of the laws of war. A United Nations-sponsored Commission on the Truth for El Salvador,...