Although warfare is thought to be responsible for high and increasing levels of morbidity and mortality in the modern era, little comparative epidemiologic research is available on the subject. Most research on past wars has been carried out for purposes of military planning. The present report provides an overview of the direct health impacts of various wars on military and civilian populations during the last 200 years. Risk factors for injury and death are analyzed. Changes in weaponry, military strategy, and medical services are found to modify the health effects of warfare.