The late historian Marilyn B. Young, a preeminent voice on the history of U.S. military conflict, spent her career reassessing the nature of American global power, its influence on domestic culture and politics, and the consequences felt by those on the receiving end of U.S. military force. At the center of her inquiries was a seeming paradox: How can the United States stay continually at war, yet Americans pay so little attention to this militarism?...