In this volume, every author as an expert in their own field addresses four overarching questions: What legacy did the Civil War leave? Did the World War I generation interpret the lessons of the Civil War, and if so, how? How did the Great War change the lessons from the Civil War era? And finally, how did both wars contribute to the modernization of the United States? highlights the striking similarities between the two wars by analyzing how the Civil War affected the American reaction to and experience in the Great War while attending to enlisted men, military officers, and political leaders. Other chapters address the environmental effects of both wars, the wars’ impacts on medicine and mental trauma, and the experiences of black American soldiers during both wars in fighting for a country that treated them so terribly. This volume, while at first appearing as a disparate pairing of conflicts, deftly opens a new window into the past and establishes an illuminating paradigm in the two wars of the long nineteenth century.