Paul Miller’s Just War and Ordered Liberty provides a fascinating intellectual history of the just war tradition, as well as an intriguing synthesis of these traditions to produce a new just war framework. That framework, in turn, can be used to address a wide array of security challenges of the twentieth century, such as rebellions, military intervention, nuclear proliferation, failed states, terrorism, and cyberattacks.

The book begins with a discussion of three just war traditions—Augustinian, Westphalian, and Liberal—and the historical transitions between them. For each tradition, Miller focuses on the writings of two to four leading proponents; for example, Cicero, Augustine, Aquinas, and Vitoria for the Augustinian tradition. In chapters 6 and 7, Miller proposes a new just war framework that combines elements of the Augustinian and Liberal traditions. He then explores his framework in chapter 8 with several short case studies including the recent US wars in Iraq and Afghanistan.

When is war just? What does justice require? According to Miller’s interpretation of the Augustinian tradition, a just war rights a wrong that has violently upset the tranquility of order. Wars for glory, profit, or revenge are not just. Wars for self-defense or to protect property are just—but so are wars to protect the innocent and punish the wicked. In addition, the Augustinian tradition stresses that peace, justice, and order must be established at the end of the war. Peace without justice is not peace at all. Enemies are to be loved, not destroyed; a stable peace requires that the rehabilitated enemy be integrated into and satisfied with the just postwar order.

Miller argues that the Augustinian tradition, which encouraged intervention for the common good, led to levels of violence that conflicted with a tradition designed to limit conflict. In response to events such as the Wars of Religion, the Westphalian tradition emerged as the dominant point of view. The legalistic Westphalian tradition argues that sovereignty is absolute: supreme authority domestically, political independence, and territorial integrity. Thus, the character of the state and behavior within its own borders should be irrelevant to the international community. The Westphalian tradition attempts to dampen international conflict by privileging borders, prohibiting humanitarian interventions, opposing rebellion, preserving the balance of power, and limiting just wars to defense of the sovereign state.

Miller contends that the Liberal tradition emerges after World War II with a focus on individual human rights. Liberals argue that sovereignty is conditional on the maintenance of peace and order. Universal human rights form an external standard against which the behavior of rulers can be judged by the international community. Liberals argue that extreme violations of human rights—genocide, crimes against humanity, war crimes, and ethnic cleansing—permit humanitarian intervention. Although the Liberal tradition does not discard the Westphalian tradition whole cloth, it creates an important class of exceptions to the rule of absolute sovereignty.

Miller believes that contemporary just war scholarship falls short because it lacks a unified framework useful across issue areas (nuclear weapons, terrorism, failed states, etc.), and it is ahistorical in that it ignores the Christian tradition on just war (pp. 155–56). In response, he constructs a new just war framework in chapters 6 and 7 that integrates two key aspects of the Augustinian tradition into the currently dominant Liberal tradition: (1) a focus on the common good and (2) an emphasis on postwar peace, order, and justice. Although Miller recognizes that focusing on the common good could significantly increase the number of “just” military interventions, he contends that the expansion of violence would be tempered by the difficult requirement to establish a just peace (p. 184).

What does justice require for Miller? The establishment of a better peace (i.e., one that reduces the causes of war that led to the outbreak of violence) but not simply any peace. As the title of the book foreshadows, a just peace requires “ordered liberty.” Politically the only just form of government involves democracy and human rights (p. 158). Economically the only just structure involves capitalism, free trade, freedom of the seas, and sanctity of contract (p. 169). Miller believes that “ordered liberty is as close to a universal value system as the world has yet seen” (p. 158). Any threat to ordered liberty at the domestic or international level justifies war. Moreover, in the aftermath of any military intervention, ordered liberty must be established (or reestablished).

The new framework forces both Miller and his readers to grapple with several interesting and complex questions. First, what role should identity play in a just war? According to Miller, liberal states are just, and illiberal states are unjust. Liberal states are sources of peace, and illiberal states are sources of war. The author advocates investing in a democratic peace among liberal states and militarily balancing against illiberal states (p. 172). Although he qualifies this at times by stating that behavior matters (p. 205), identity is central to his new just war argument. If a liberal state is attacked, it is just to defend it. If rebels express liberal views, you can intervene in a civil war on their behalf. If you militarily intervene in a humanitarian crisis, you have a moral obligation to establish a liberal regime after the war. However, Miller rejects the liberal imperialist claims that war is justified against all illiberal states (pp. 197, 218) and that a threat to ordered liberty requires (as opposed to permits) a military response (p. 189).

Second, should state-building play a central role in US foreign policy? According to Miller, any military intervention, humanitarian or otherwise, must end with ordered liberty. This would require the establishment of democracy and capitalism in the target country, as well as the integration of this country into the liberal international order. Miller argues that the withdrawal from Iraq in 2011 (p. 212) and Afghanistan in 2020–21 (p. 215) were moral failures because the job of creating a liberal order was incomplete. Importantly, instead of seeing these cases as failures in state-building, Miller contends that the US government did not commit sufficient time and resources to the state-building effort in the first place (p. 251).

The state building issue raises additional questions. Can liberal leaders accurately estimate the cost of establishing ordered liberty before choosing to intervene? Although Miller touches on problems of motivated and cognitive biases in the closing paragraphs, it is clear that US leaders have engaged in wishful thinking with respect to establishing postwar stability for the last 40 years (e.g., Afghanistan, Iraq, and Somalia). How long is enough? Although Miller says certainly not forever, he advocates staying in Afghanistan until the job is done (p. 216). Finally, how long will the public in a liberal state support the use of troops and the expenditure of dollars to complete the state-building project? If liberal publics are impatient, the requirement for ordered liberty may prohibit any military intervention.

Third, what is the proper role for multilateral organizations in sanctioning just war? Miller explicitly states that he is not concerned with unilateral (or bilateral) interventions by states (pp. 201–2, 235). If the cause is just, the execution is just, and the result is ordered liberty, then Miller is comfortable with the intervention. Although UN sanctions can make the case for just war stronger, multilateral permission is not necessary. But in cases of humanitarian interventions, the propensity for decision makers to see what they want to see (i.e., motivated bias) or cherry pick information that seems to support their position (i.e., confirmation bias) raises the issue of the wisdom of the crowd. The requirement to persuade other states of the severity of the humanitarian crisis to justify the violation of sovereignty seems vital to balancing the Westphalian prohibition on intervention with the Augustinian permissiveness on intervention.

Fourth, should we require the establishment of ordered liberty in all cases of military intervention? Miller explicitly raises this issue with respect to Afghanistan after 9/11: the United States could have invaded Afghanistan to destroy al-Qaeda and to topple the Taliban for supporting groups that engaged in international terrorism (p. 215). It could have then left the country quickly in the hands of various illiberal warlords. Miller sees this realist approach as inherently unjust. But if transforming Afghanistan into a liberal image of America is unlikely to succeed or be prohibitively costly, is order without liberty a just option?

Finally, is a liberal economy a necessary condition for a just war? Miller uses liberty as a broad term encompassing both political and economic liberty. However, he does explicitly state that capitalism and free trade are essential elements of ordered liberty (p. 169). By including both economic and political liberalism, he has doubled the amount of state-building required in an intervention. Moreover, there is far less of a global consensus that American-style capitalism is just. Forcing capitalism on states may well be perceived as economic imperialism and undermine how just a military intervention is perceived by citizens in the target country.

Miller’s thought-provoking synthesis of just war traditions will provide scholars and practitioners with an excellent starting point for debating how to reduce conflict by finding the right balance between respecting state sovereignty and engaging in morally justifiable interventions for the common good.