Assessment of the extent of civilian casualties during times of conflict presents significant challenges in data collection, quantitative methods, interpretation, and presentation. In this article, we briefly consider the motivation and use of casualty accounting and review historical approaches to these questions with illustrative comments on the US Civil War, World War I, World War II, and other conflicts. We provide an overview of several accounting methodologies including excess mortality, epidemiologic surveys, direct and indirect counts, multiple list estimation, and crowdsourcing. We reflect on the evolution toward modern approaches to casualty assessments, permitted by both a deeper understanding of human rights and by contemporaneous technological advances in data collection techniques. Our goal is to introduce several areas of research that deserve attention from social science historians and statisticians.