As I write this review, the United States is engaged in (another) predominantly aerial military campaign, this time against the so-called Islamic State (also known as ISIL or ISIS) in Iraq and Syria. What norms influence American decisions concerning when and what to bomb? Can a war that relies mostly on air power ultimately be successful? These questions, among others, lie at the heart of ongoing and urgent debates about the relationship between military strategy, law, and ethics in the 21^st century. The timely contributions in Matthew Evangelista and Henry Shue’s The American Way of Bombing go a long way to answering these questions, shedding considerable light on how norms regarding aerial warfare have evolved and where they might be going. The book makes a valuable contribution and will be of great interest to students, scholars, and practitioners alike.

The major strength of the volume is the diversity of expert viewpoints that elucidate historical trends while also offering critical reflections informed by theory and empirical case studies. Military historians, practitioners, legal experts, political scientists, philosophers, and anthropologists weigh in on the evolution of bombing norms and potential future trends. In the editors’ own words: “Our purpose of this book is to try to identify some pattern for the changes that have occurred and evaluate plausible explanations for those changes” (p. 4). The authors focus on the United States because of its global military preeminence, its frequent engagement in aerial bombardment across the globe, and most importantly, its past (and future) influence on normative change.

The intelligent structure of the book exposes the reader to a variety of ways of thinking about the changing norms of aerial warfare. The first section casts a historical gaze, tracing the evolution of norms from the first instances of flight to the post-9/11 era. Tami Davis Biddle’s chapter sets the stage by discussing the early history of bombing, locating the “battered” norms calling for greater protection of civilian communities amidst the unprecedented numbers of civilian deaths during World War II (p. 28).

The rest of the section explores how the United States moved towards a norm of more discriminatory bombing. Sahr Conway-Lanz picks up the historical thread with a jarring examination of the trends in the Korean War, but also finds a kernel of ethical standards despite the ashes of civilian horror. Neta Crawford’s standout contribution brings us to the modern day by examining the normative stances during the major U.S. bombing campaigns from the Vietnam War to the post 9/11 wars. She highlights how changes in the minds of elites and the general public regarding targeting civilians, the elite’s understanding of military necessity, and concern for military effectiveness are all causal factors that have influenced bombing norms. The historical section concludes with Charles Garraway’s crisp discussion of the evolution of the laws of war, and a plea for a pragmatic, realistic legal regime informed by ethics.

We are provided, thus, with a portrait of evolving U.S. norms, from the ethical kernel found amidst the horrors of the WWII and Korea, to what Crawford identifies as “institutional level” changes that mitigate the risk and harm to civilians during the 1990s (p. 86).

The second section of the book begins with a cautionary tale about the importance of history. Charles Dunlap labels the role of history in debates about the legal and ethical norms of airpower as “frustrating” (p. 110) and “temporally limited” (p. 112). Dunlap challenges those interested in participating in the dialogue about bombing norms to become more familiar with the technical aspects of the military process. The critical reexamination of the evolutionary trend presented in the first section continues with Janina Dill's tightly argued chapter that examines competing legal notions of the principle of distinction. She takes inspiration from existing positive international law (the 1977 Protocol Addition to the Geneva Convention) to offer a more restrictive view compared to the standard employed recently by the U.S. military.

The chapters by Henry Shue and Richard Miller offer sober reading that adds a further critical edge to the book. Shue explores the complexities of balancing among military advantage, force protection, and constant care of civilians. Using the 1991 U.S. bombing campaign of Iraq, he argues that despite more restrictive norms on paper, the armed forces can get the balance wrong. His discussion of the fallout from targeting the Iraqi electrical grid is particularly illuminating in this respect. Miller casts further critical doubt on the view that bombing norms really offer enough protection to civilians; his case studies of the U.S. bombing of Iraq and Afghanistan post 9/11 suggest that changes are really about strategic rationales rather than real concern for civilian well-being.

Up to this point, the book succeeds in its task of identifying and critically evaluating changes in bombing norms. But as it moves into the third section on constructing new norms, the book (perhaps inevitably because predicting new norms is a most difficult task) loses its shape. Margarita Petrova’s excellent chapter shows how NGOs successfully turned the principle of military necessity on its head to lobby for the banning of cluster munitions, suggesting that this might be a similar framework to confront future problematic military technologies. However, the subsequent chapters on drones by Hugh Gusterson and Klem Ryan, while very interesting in their own right, do not explore this thread, and thus the book misses an opportunity to make an even deeper contribution to the use of force debates. Gusterson considers how drones re-spatialize war, change its pace, and rework notions of military honor and courage; Ryan argues drones undermine certain aspects of international law by disassociating the battlefield. While these points are well taken, echoing some of the claims made in the broader literature on drones, the volume does not offer a much-needed alternative norm that could structure drone use.

Drones have indeed eroded some of the existing norms regarding the aerial use of force, but the story does not end there. The norms governing drone use are a contested space. Since Amnesty International’s initial criticism of the first U.S. drone strike outside a specified battlefield (2002 in Yemen), a series of important official reports from the United Nations, Amnesty International, Human Rights Watch, and other NGOs and academic clinics have consistently challenged the evolving U.S. position. Given the promise of the volume, one would like to have seen more thought given to the direction where norms governing drone use might or should evolve, and what impact these (and other) groups might have on shaping future norms.

Mary Ellen O’Connell’s chapter on banning autonomous killer robots does provide such an ambitious normative claim. She hopes to set the normative agenda so that such hypothetical weapons never become “just another weapon.” To do so, she emphasizes the need for multilateral negotiations that would promote the new anti-killer robot norm publically, demonstrate its coherence with existing norms, and alter the external environmental conditions so as to be more favorable to this new norm. Whether global society gets there is an open question, but O’Connell is bold enough to provide a would-be road map.

To conclude, The American Way of Bombing succeeds in exposing the reader to the complex story behind the evolution of bombing norms. The historical trend towards greater protection of civilians is challenged by insightful critiques that draw on illuminating examples from the annals of U.S. bombing campaigns. Indeed, reading the critical chapters placed a seed of doubt in my mind: What if the historical trend described is not as strong as we, perhaps naively, imagine? Here Biddle’s ominous conclusion about targeting civilians in World War II reminds us of the relevance of remembering history, and continuing the discussion of bombing norms that this book helps to move forward: “This crescendo of destruction was orchestrated by democratic states that responded with fear-driven fury… It revealed the full extent to which peoples who considered themselves civilized—protectors of human rights and Enlightenment principles—could be brutalized by fear … and by the uniquely pernicious spiral of total war” (p. 45).