The two centuries from 1800 to the present day are marked by the increasing efficiency of the means by which humans inflict violence. The myriad causes of violence differ little, if at all, from the other periods analysed in the first three volumes of this collection – greed, envy, lust, anger, vanity and shame produce interpersonal violence while differences in race, language, religion, class or creed are common prompts justifying mass-scale violence. The novel aspect of the years explored in this volume largely revolves around the impact on violence of technological advances. The energy unleashed in the Industrial Revolution spurred the rapid growth in technologies supporting the execution, organisation, annotation and representation of violence from 1800. The digital revolution of the late twentieth and early twenty-first centuries accelerated many of these trends with the advent of the capacity to move information instantaneously around the globe. This volume examines the impacts of this technology-enhanced efficiency with its large-scale acts of violence – mass deaths in minutes – hitherto unseen in human history. It also tracks the ways that increased access to stories of and information about violence has changed public perceptions of the parameters of legitimate violence at both the mass and the interpersonal level. The decreasing public appetite for violence exists simultaneously with expanding, new forms of leisure which have rendered representations of violence banal.