The intellectual history of just war thinking should be understood as unfolding in three traditions: the Augustinian, the Westphalian, and the Liberal. The Augustinian tradition of just war thinking rested on the idea that natural law exists and should guide human social and political order to fulfill natural human moral aspirations; that sovereignty means responsibility for the common good; and that justice should guide states to use force to defend the common good. In the Westphalian tradition, sovereignty evolved from defense of the common good to defense of international borders, and just cause shrank to encompass only territorial self-defense. In the embryonic Liberal tradition, concepts like human rights and accountable governance do the work that natural law and justice did in the Augustinian tradition: external standards outside and above the state used to judge the state’s legitimacy. The Liberal just war tradition allows war to vindicate the rights of individuals suffering under a humanitarian emergency, insists on respecting individual rights in how war is fought, and understands the vindication of individual rights a crucial part of ending wars justly.

The Augustinian, Westphalian, and Liberal traditions are each insufficient to guide ethical reasoning about war today. The answer lies in a partial synthesis among them, especially the Augustinian and Liberal traditions. The language of natural law and human rights are especially useful because they can make moral claims about the common good across the boundaries of culture and religion. In the Augustinian Liberal perspective, the principles of ordered liberty, human rights, and human flourishing do much the same work that natural law and justice did for the Augustinian tradition as an external standard above the state, to which the state must be accountable. Justice requires the vindication of rights but is not exhausted with rights because it also requires the sustainment of conditions required for rights to be meaningful, to promote human flourishing—which is a long way of saying that justice requires ordered liberty. Sovereignty means responsibility for the common good, which means responsibility for establishing, sustaining, and defending a system of ordered liberty at home and abroad. And ordered liberty is as close to a universal value system as the world has yet seen.

This essay on Elizabeth Lippincott McQueen analyses the ways in which gender intersected with international thought-as-spirituality. McQueen can hardly be regarded as a conventional intellectual: she was a charismatic entrepreneur thriving on a localized form of techno-optimist internationalism in 1930s Southern California. Her religious formation as a Christian Scientist inclined her to understand and experience the act of thinking as a practice that could change the world. McQueen’s conversion-like encounter with aviation prompted her to transfer a spiritual model to a political project - the promotion of world peace and Anglo-American liberal empire. She strategically drew on gendered notions of sociability and spirituality, and developed her gospel of aviation during a time when women were integral to the rise of a new technology. Once commercial aviation was securely established in the United States, women were relegated to service tasks, in a move that eerily resembles the formation of IR as a discipline.

During the Reformation and the Age of Exploration, just war thinkers were forced to reexamine the premises on which the Augustinian tradition had stood, including their understanding of natural law, justice, and sovereignty. This chapter examines three thinkers crucial to that transition: Alberico Gentili, Francisco Suarez, and Hugo Grotius. They are part of the Augustinian tradition, but clearly show signs of subtle departure from their predecessors. Grotius, especially, is a hybrid between the Augustinian past and Westphalian future. They understood themselves to be engaged in a project of continuity: they wanted to salvage and reinterpret the intellectual inheritance of Christendom and reapply it to the changing and fracturing landscape of their day. But the new age inaugurated by the treaties of Westphalia transformed it in subtle but important ways, most prominently by secularizing its discourse and changing its understanding of natural law.

Emily Balch is a familiar figure to historians of the early twentieth-century transnational women’s movement, not least because of her central role in the Women’s International League for Peace and Freedom (WILPF). Yet, there is no doubt that Balch was also a thinker engaged in conversations now recognized as squarely belonging to the history of international thought. These include debates on race and immigration, economic interdependence, the reform of colonialism, and visions for a world society. There were contradictions within Balch’s thought but her empirical research nonetheless challenged some of the racist stereotypes within American International Relations in the 1910s and 20s. Balch was never interested in separating the domestic from the international. Her starting point remained her ‘fellow citizens’ and the contexts that shaped their lives, whether these were the ethnographic realities of East-Central Europe or the impact of the United States’ occupation of Haiti.

Like several other interwar liberal internationalists, F. Melian Stawell was a classicist by training, set for an illustrious career at Cambridge working simultaneously on the ancient Greeks and contemporary world order. Stawell is best known as the author of The Growth of International Thought, a book increasingly cited, if not read, as the first to use the term ‘international thought.’ This chapter offers the first close reading of the text itself and of its major influences and context, challenging the (gendered) distinction between international and internationalist thought. Indeed, it argues that it was interwar internationalist international thought that inspired some contemporary IR academics to write for broader audiences, and women to engage with international politics. Overall, the essay both makes a case for including a range of genres in histories of international thought, whether work that had a primarily pedagogic or political rather than scholarly function.

I draw insights from the Augustinian and Liberal traditions and, to a lesser extent, the Westphalian tradition to offer ordered liberty as a central organizing concept for just war thinking. Ordered liberty is the rightful purpose of statecraft, the just aim of the state—which means it is also the just purpose of warfare. This helps answer the two questions animating this book. When is war just? The violent disruption of ordered liberty is the “injury” in response to which force may be used and war may be justly waged. What does justice require? Justice requires the vindication and restoration of ordered liberty in, through, and after warfare. The upshot of this argument is that while just cause is more expansive than is conventionally understood, the responsibilities of post-conflict restoration are commensurably far higher.

Vera Micheles Dean’s career took her from a PhD at Radcliffe to the Foreign Policy Association and then to the University of Rochester and New York University. As a scholar, her theoretical stance was realist with a thorough grounding in social psychology. Yet, despite her academic grounding, she was a public intellectual, embracing a ‘common-sense cosmopolitanism’ that sought to make the world relatable to ordinary citizens. In her writings, Dean acknowledged the centrality of the non-Western world in the Cold War, an analytical move taken decades before Cold War historians and IR scholars began to ‘decenter’ the United States and the Soviet Union in their accounts. An expert on Soviet Russia, Dean argued for a policy of mutual understanding, advocating collective forms of economic organization and the pooling of sovereignty. Ideologically, she was committed to global social democracy, anti-racism and, importantly, a holistic understanding of security that encompassed psychological aspects.

The 1990s were supposed to usher in a new world order and more peaceful modes of transformation in international politics. Freed from the constraints of Cold War confrontation, many strategists predicted retrenchment in US global strategic commitments. However, these hopes ran headlong into the so-called ‘new wars’ of the 1990s, such as those in parts of Africa and the Balkans. This was not part of the script. To analysts who had for decades focused their attention on nuclear deterrence or the prospect of major war against the Soviet Union, these conflicts seemed to appear out of nowhere. That they were often continuations of Cold War proxy wars or sparked precisely due to the collapse of longstanding structures was largely irrelevant to a public increasingly exposed to images of human suffering in faraway places. Calls for policymakers to ‘do something’ gathered momentum.

Leaders at the Pentagon were generally opposed to involvement in lowintensity conflicts. After all, in 1991 the military had just demonstrated its prowess in high-end conventional war, thinking that all wars would have that particular shape. Meanwhile, the George H.W. Bush administration, lacking the guiding star of combating communism, steered a cautious path through this new and unfamiliar post-Cold War landscape. Colin Powell, as Chairman of the Joint Chiefs of Staff, was in the process of doubling-down on Weinberger's earlier restrictive doctrine, now adding the criteria of overwhelming force and clear exit strategies to the list of fundamental principles that would guide the use of military force. In 1991 and 1992, Powell and the Joint Chiefs were actively advising against military involvement in peripheral conflicts such as Somalia or Bosnia.

Yet political elites did not necessarily see things this way. The sense of moral mission that had motivated America's confrontation with the Soviet Union was now, in victory, strengthened by a renewed confidence that its liberal republican system represented the world's future, if in fact the end of history had not already arrived. This was joined by the kind of self-assurance that came with its status as the world's sole superpower, firmly underpinned by its conventional military dominance, as recently displayed during the Gulf War. Some commentators urged policymakers to take advantage of this ‘unipolar moment’ given that the US could now more safely intervene where it wished with little serious risk of sparking a major inter-state war.

The Second World War confirmed America's ascent to great power status. The nation emerged out of the war with great wealth, unparalleled military capabilities and a series of bases spread around the world. This was not just a traditional territorial empire exercising significant and in some places direct control over foreign possessions; the United States also commanded huge indirect global influence, primarily through its role in shaping the post-war international architecture. It had vast commercial interests and its dominance was apparent, not only in traditional metrics of power but in cultural and ideological terms too. Of course, large swathes of the globe were firmly within the Soviet orbit or otherwise under the influence of regimes subscribing to forms of communist ideology, which American institutions, investments and ideas struggled to penetrate. But this applied mainly to the ‘wasted landscapes of Europe's devastated east’ – the USSR was in disarray in the years after the war, and other communist movements were fighting bitter struggles for survival. American hegemony was the dominant fact of the post-war order, and this remained a constant of world politics up to the present day.

Preoccupied with a convergence of intersecting geopolitical, economic and ideological concerns, the country was led by men who believed America required a preponderance of power to protect and promote its vital interests. Porter usefully identifies four key factors that compelled policymakers to aggressively defend American primacy in the new geopolitical context: the nation's growing power after the Second World War encouraged it to ‘pursue security through expansion’; various crises and strategic shocks – such as Pearl Harbour or the North's invasion of South Korea in 1950 – inspired a sense of growing vulnerability requiring preventive action beyond its shores; tempted by its growing power, America's universalizing liberal traditions encouraged it to shape the world in its own image, confident that greater security would come from a world community of like-minded democratic republics; and finally, a ‘self-propelling dynamic of empire’ meant its growing global purview created new frontiers and with it new insecurities, commitments and anxieties. The practical measures this all entailed required America to overturn decades of foreign policy shibboleths warning about large military establishments, entangling alliances and going abroad seeking monsters to slay.