War has reliably ravaged humanity in every era and in virtually society. Some say it will always be with'us, for the propensity for violence is an indelible human trait, as if mass killing was somehow etched into human genes. Others are more optimistic, convinced that someday humans will overcome their aggressive urges and eradicate war from the planet. Whatever the case, perhaps we can draw some encouragement from the fact that the ethics of war-the philosophical study of the morality of warfare--continues to shed light on the subject, yielding more understanding than most people would think possible.