The great strength of this book is that it manages to be thought-provoking and entertaining at the same time, challenging the way readers think about war but doing so with a light touch. Brooks is a law professor who worked as an adviser to a U.S. undersecretary of defense from 2009 to 2011, a position in which she witnessed how technological change and the nature of contemporary warfare have blurred boundaries that once divided war from peace, the military sphere from the civilian one, and armed forces from police departments. This blurring has made it harder to tell when normally criminal acts, such as forceful detention and killing, become lawful and acceptable acts of war. Blurred lines have also drawn the U.S. military, a generously resourced and usually competent arm of the government, into pursuits for which it is not well suited, such as postconflict reconstruction. Brooks is generous toward her former colleagues, portraying their failures as the results of contradictory pressures and imperfect organizations. She writes with knowledge and wit as she tries to identify best practices for a world in which war and peace exist on a complex continuum.