This is a theoretical work that makes two closely related arguments. The first is that globalization has taken us from the discrete “threats” of the Cold War to the generalized “risks” of the Global War on Terrorism, leading to the practice of new modes of strategy. These strategies entail unforeseen consequences that may be worse than the original risks. Mikkel Vedby Rasmussen's work is at its best when detailing these “boomerang effects,” particularly when addressing the impact of the “revolution in military affairs” (RMA) undergone by the United States.

Rasmussen's second argument is that this new focus on risks requires a paradigm shift in how we understand strategy, from a Clausewitzian “means-end rationality” in which political ends are accomplished via military means, to “a reflexive rationality for dealing with risk” (p. 8). While means-end rationality seeks certainty whenever possible, reflexive rationality recognizes that risk can only be managed, not eliminated, and that new risks may arise due to responses to old ones. Addressing risks thus requires continuous management and attention primarily to future events, in particular to potential boomerang effects.

This argument suffers from the conflation of great-power realism and rationality. The two opening chapters, covering definitions of strategy, rationality, and risk, are indicative of this. Rasmussen equates realism with the approach of means-end rationality, of which “hypotheses of game theory” (p. 98) are said to be one type. In doing so, he limits the domain of existing forms of rationality to consideration of great-power interactions; in this light Al Qaeda is only a minor state, far less relevant than China (p. 31). His conflation closes the door on productive modes of analysis that would clarify definitions and logic central to his argument.

For example, consider Rasmussen's definition of risk: “a scenario followed by a policy proposal for how to prevent this scenario from becoming real” (p. 2). This definition combines possible outcomes with the likelihood of those outcomes, as well as with a proposal for avoiding the outcome. Quantitative comparisons of risks become difficult in this context, as the metrics by which we judge the outcomes of policies are not the same as those used to measure the probabilities of outcomes. The same problems occur in his definitions of rationality: He offers means-end rationality, reflexive rationality, “value-based” rationality (p. 202), and generic different rationality (p. 166) without an explanation of their fundamental differences. Indeed, they all seem to be variants of the typical (possibly bounded) rationality utilized by rational choice theorists. Rasmussen suggests that users of means-end rationality do not “argue in terms of … probabilities” (p. 198) and have “little to say” (p. 11) about managing risks. Yet this is not true; rational choice assigns distributions to outcomes and specifies how these change, conditional on actions. Recent examples of this approach are Walter Enders and Todd Sandler's The Political Economy of Terrorism (2006) and Robert Powell's “Allocating Defensive Resources with Private Information about Vulnerability” (American Political Science Review 101 [November 2007]: 799–809). Accordingly, it is not necessary to invoke any “risk society”; existing theory is sufficient.

Though it does not advance theory in the sense Rasmussen claims, The Risk Society at War does do an admirable job in addressing issues that arise when one moves from the singular threat and clear outcome of mutually assured destruction (MAD) to a future of multiple, uncertain risks. In the former case, there was wide agreement that the possibility of MAD rendered irrelevant boomerang effects; thus, we ignored actions that led eventually to wars in Iraq and Afghanistan. With outcomes less costly, however, our desire to minimize bad outcomes and achieve certainty still leads us to ignore boomerang effects, even when we know they can be worse than the outcomes we originally tried to avoid.

Chapters 3 through 5 make clear the consequences that might arise from the RMA, pre-emptive and preventative doctrines, and shifts in the targets of warfare from established states to nonstate actors. Rasmussen notes that the RMA alters America's strategic framework because it reduces uncertainty, making war more manageable and reducing casualties. This naively seems like a pure positive, yet as he discusses, there are numerous boomerang effects. Lower costs of war make it a more attractive option; this leads to more war, not less. Preventative wars to minimize bad outcomes are proposed. Since potentialities arise continuously, military actions are frequent, breaking down institutional checks on their use.

Increasingly infrequent casualties make each death more important politically, resulting in a greater focus on projecting force from a distance and a bureaucratization of the armed forces. Weak foes rationally respond with asymmetric warfare; the Iraqi insurgency is used as an example. A bureaucratized military focused on optimizing the RMA, however, is not trained well to respond to such tactics. Wars get drawn out with continuous casualties.

Strong foes seek the RMA themselves, often via technologies that are in the private sphere. Keeping ahead of all possible rivals entails greater spending on the RMA than might be optimal, particularly when parity of strength might result in “pop-up” wars, in which any revealed military capacity is instantly destroyed. Brakes to such spending are limited: The range of potential bad outcomes is so large and ill-defined that it is easy to politicize intelligence on risks, especially when warfare grows too deadly for the media to experience.

Even when the state cannot make this argument, it can turn to arguments based on vague, difficult-to-contradict statements about freedom or democracy. Such arguments also allow states to bypass the “UN approach” to war, which limits legitimate war between states, particularly in conflicts with nonstate actors who do not fall under the purview of the United Nations.

These are all important insights. It is unfortunate that the book's “risk society” frame detracts from their power, diminishing the text's impact.