International and intra-state conflicts have become more deadly for civilians over the past 120 years. This ascending arc of civilian fatalities since 1900 forms part of a larger twentieth- and twenty-first-century phenomenon increasingly identified as the ‘civilianization of war’.Footnote ¹ Wars between states as well as civil conflicts within them have seen non-combatants systematically targeted.  It is civilians who suffer a large proportion of security force violence, insurgent attacks and counter-insurgent repression. At the time of writing, affording better protections to the most vulnerable population groups, including women, adolescent males, ethno-religious minorities and displaced persons, remains the most difficult task in conflict limitation and peace enforcement. A first step in pursuit of these objectives is to study this ‘civilianization of war’, in which civilians are often not just the principal victims of intra-state conflict but its foremost targets as well. The aim of this study is thus to demonstrate the ways in which the distinction between civilians and military forces – what we call the civil–military divide – has changed, whether in thought or in practice.

What does the distinction between civilians and soldiers, combatants and non-combatants, amount to in theory or in practice? The increasing complexity of this question quickly becomes clear when one looks at the debate over the ratio of civilian to military losses in various conflicts over the last century. A 2009 study by Adam Roberts showed the ratio for the war in Bosnia Herzegovina (1991–95) to be roughly 2:3, while in Iraq (beginning in 2003) it was 5:1 or possibly as low as 3:1.Footnote ² Similarly, over the last century, high levels of internal displacement and forced population removal have been recurrent features of intra- and interstate conflict. From the traumatic population exchanges that accompanied the Greco-Turkish War (1919–22) to the displacement of European populations in the aftermath of the Second World War, civilians have been compelled to move under threat of violence or discrimination as a direct consequence of prior conflict.Footnote ³ So, too, the territorial partitions triggered by the end of European colonial dominion in the Indian sub-continent, in Palestine and elsewhere were accompanied by systematic targeting of refugee populations by security forces and sectarian vigilante groups.Footnote ⁴ What do such instances of mass violence against civilians imply? While civilian casualties have risen markedly relative to military ones, that does not signify the inevitable failure of protections in place for civilian populations, or an inexorable shift towards new forms of conflict in which all risk being targeted. As important as the methodological debates around these calculations and the growing complexity of this phenomenon are, it is the tremendous variation in the proportion of civilian casualties that captures the reader’s attention and is the focus of this work. It draws on case studies from conflicts in diverse regions and settings over the last century to investigate why, during this period of rising civilian casualties, the civil–military distinction is so dynamic and unpredictable.Footnote ⁵

The extent to which civilians are protected in war depends substantially on that divide’s local forms and practices, a phenomenon analysed by the chapters in the book’s first section. As the chapters demonstrate, the nature of armed conflicts is closely related to the extent to which civilian populations are mobilized, becoming integral to combatants’ war efforts. This theme runs throughout the chapters but is especially prominent in the book’s second section, which is devoted to aerial bombing. The development of long-range bombing aircraft was made possible by new technologies that arose at the beginning of the twentieth century, and their devastating strategic objective, directly attacking the home front, threated to collapse the distinction between combatants and civilians. A third theme is the matter of civilian protections and their enforcement. The aim here is to explain whether – and why – systems of laws, treaties, the work of international organizations (IOs) and non-governmental organizations (NGOs), and other factors favouring the respect of normative standards hold any sway once conflicts break out. Highlighting interactions between these three themes, the chapters thus help identify what lies behind the tremendous variations in the treatment of civilians in conflict.

Our study of the civilianization of war begins with the First World War’s outbreak in 1914, a point of departure for fundamental changes in the way wars were fought and, in consequence, for the reconceptualization of the distinction between civilians and soldiers. Modern industrial war, conducted by intra-continental alliances based in the global ‘north’ (primarily Eurasia, North America and their imperial peripheries), demanded unprecedented sacrifices from all social strata. Political systems and societies of every stripe were pushed to the breaking point. Never before had industrialized nations invested and mobilized so much of their human, financial and material resources in the service of war.Footnote ⁶

These transitions signified the emergence of ‘Total War’, a form of inter-societal conflict that implicated civilians more directly as economic producers, as cultural embodiments of an idealized home front, and, most pertinent to us here, as targets for attack, notably through the development of strategic blockade and bombing.Footnote ⁷ Nor did ‘total war’ end neatly alongside armistice agreements and treaty settlements. Violence persisted, much of it internecine and inter-ethnic, in what some scholars describe as the ‘Greater War’ that encompasses the conflict’s unsettling aftermath. Their efforts brought little immediate reward. For many, the First World War lingered on in smaller regional conflicts, in revolutionary upsurges and counter-revolutionary backlashes, and in more widespread paramilitarism.Footnote ⁸ Others reacted by spurning state violence altogether. Transnational movements, many of them internationalist in inspiration, strove to ensure that such global conflict would never recur. Diplomatic efforts were even made to restrict, outlaw or eliminate war altogether, the Kellogg–Briand Treaty of 1928 foremost among them. Disarmament, albeit fleetingly, became a shared political goal and a popular rallying cry. The infant League of Nations, meanwhile, represented a new form of standing IO, one that made fostering peace and protecting civilians (particularly threatened ethnic minority groups) central to its global mission.Footnote ⁹

Many recent studies have also argued that the interwar period signified the arrival of NGOs on the international scene, notably the panoply of lobby groups campaigning against armaments and their indiscriminate use. The impetus behind this turn to disarmament was, in part, a matter of ethical judgement and ideological preference; in part, a matter of economic and strategic calculation. Whichever was the case, while the distinction between the military and the civilian was badly eroded by the war, its innate value was debated and publicly defended by a growing number of states and organizations during the 1920s and beyond.Footnote ¹⁰

The advent of another global conflict unleashed an even greater transformation in the codification of civilians, refugee populations, displaced persons and other victim groups. Informed by the failings of the League of Nations and the collapse of the post-1919 peace, the victors in this Second World War endorsed stronger collective security systems and a United Nations organization (UN) invested with greater powers than its predecessor. Much of the UN’s initial workload involved the rehabilitation and relief of civilian populations in occupied territories.Footnote ¹¹ But even as these tasks of social reconstruction proceeded, the collective security arrangements outlined by the wartime Allies were refashioned into the Cold War’s adversarial alliance blocs. Hidebound by the dominant powers within its executive Security Council, the UN mirrored these Cold War divisions. At the same time, the geopolitical focus of conventional warfare in the second half of the twentieth century was shifting south and eastward. Nuclear weapons raised the stakes involved in a direct conflict between the superpowers. Less so elsewhere: both the use of the atomic bomb and subsequent plans to drop further ‘field’ weapons occurred in Asia. This reflected more than US and European strategic thinking about East Asian regional flashpoints from Korea to Vietnam; it carried ugly racial undertones as well.Footnote ¹²

Set against this fraught atomic peace, the spectacular late twentieth-century collapse of European colonialism ushered in an era of tremendous violence in the developing world. From South East Asia to the Caribbean, formal colonial empire disintegrated in the thirty years after 1945. Even in dependent territories in which open warfare was averted, labour coercion, racial discrimination and consequent human rights abuses were endemic. In other colonial regions – among them Indonesia, Indochina, and much of North, East and Southern Africa – wars of decolonization were characterized by a massive mobilization of colonized populations but relatively little mobilization by Europe’s declining colonial powers.Footnote ¹³ Europeans may have been less directly affected by the end of the empires built in their name, but decolonization, its partitions, its violence and its bitter legacies wrought as much global geopolitical change to the international system as the twentieth century’s world wars.Footnote ¹⁴ Although slow to register at first, decolonization also changed the operational focus and juridical basis of the UN and its affiliate aid agencies.Footnote ¹⁵

Despite the Cold War stasis, the post-1945 period witnessed significant advances in international humanitarian law, some of them related to the belated recognition of developing world societies as actors within an international system whose parameters were defined not by the end of empire but by the preceding Second World War.Footnote ¹⁶ From the Holocaust to the horrors of Rwanda in 1994, the past century’s genocides also fuelled efforts – tragically, always after the fact – to criminalize the targeting of communities on the basis of ethnicity or other presumed cultural attachment. From the 1948 Genocide Convention to the codification of the UN’s ‘Responsibility to Protect’ doctrine in the early 2000s, ‘humanitarian interventionism’, its impulse well captured in the phrase ‘saving strangers’, has tested the limits of international cooperation and, with it, the ethical standards of states and societies.Footnote ¹⁷

This era was marked at its 1945 opening by the arrival of nuclear weapons. Although their use has been threatened on several occasions, they have not been used since, and thus fall outside the scope of this study. Equally, the proliferation and use of weapons of mass destruction has become an extremely important issue, but is marginal to the violence witnessed over the last century and, therefore, to the approach adopted here.Footnote ¹⁸

By investigating these critical transitions in the nature and practice of war over the last century, this chapter offers an alternative perspective on current, twenty-first-century conflicts. The turmoil in Afghanistan evinces factors often seen as ‘northern’ (modern forces relatively well sensitized to international norms yet often inflicting high civilian casualties) alongside factors often seen as ‘southern’ (highly mobilized insurgent forces making use of technology and international norms as weapons in their campaign). If these asymmetries are relatively well known,Footnote ¹⁹ this chapter pinpoints something else. When contemporary conflicts are framed in the setting of their twentieth-century antecedents, the essential continuity between them lies in the highly dynamic manner in which the changing nature of war, belligerent mobilizations and international norms reshape each conflict’s civil–military divide.

To understand how the changing nature of war expanded and contracted the division between civilians and soldiers, one next needs to explore its connections with two related factors. The first is the relationship between the military and home fronts, a connection most easily understood in terms of mobilization. As the experiences of 1914–18 illustrated with dreadful clarity, forms of inter- and intra-state conflict are to a large extent determined by the resources that are mobilized for them.Footnote ²⁰ Regimes, be they democratic or authoritarian, integrate the domestic population, the home front, into their calculations when planning or engaging in conflict.Footnote ²¹ The economic potential and cultural integrity of a civilian population must be upheld. Conversely, the same calculation pertains for all warring parties, making a nation’s mobilization a key target for its enemies, one that modern technology has often made all the easier to strike.Footnote ²²

There is another aspect of mobilization that adds to its significance in a study of civil–military divides. The greater wartime demands imposed on home front civilians strained social cohesion, imposing the need for countervailing efforts to ensure that communities did not crack under the burdens they were forced to shoulder. Monitoring the home front in order to better sustain it thus became a crucial element in a belligerent’s strategy. The conflict’s objectives and the means and costs that came with their attainment have increasingly been subjected to the test of popular support. While efforts to sustain national or communal unity can be largely matters of rhetoric and propaganda, the greater need to justify decisions for war carries over into the wartime requirement to explain the suffering being endured. It bears emphasis that the creation of the League of Nations and the UN owed much to wartime calculations by the Allies regarding the need to legitimize the immense sacrifices being demanded of their populations.Footnote ²³ Moving into the late twentieth century, a crucial policy lesson of the war in Vietnam for many in Washington was that in an age of mass communication, public opinion would tolerate only so much sacrifice. Public sufferance tended to diminish when the conflict lacked the existential significance to the United States of, say, the Second World War.Footnote ²⁴ Stirring or sustaining popular support or mobilizing human and material resources for a conflict judged by many to be not only inessential, but indefensible, proved near impossible. Mobilization also provides a link to the third and most recent factor in the civilianization of war: international norms.

The very notion that civilians deserve different protections in armed conflict from those afforded to combatants raises difficult ethical questions. For, as Maja Zehfuss reminds us, the implication behind this distinction is that certain forms of killing remain permissible while others do not. Recognizing civilians’ special claims to protection might be taken to imply that non-combatants do not contribute to the war efforts conducted in their name. Conversely, suggesting that the violence to which civilians are frequently exposed in war should somehow be ‘proportionate’ to the strategic objectives sought by their attackers risks putting civilian populations at even greater risk.Footnote ²⁵ These considerations have become increasingly important over the past century as a system of international protections for civilians has widened.

The late nineteenth century witnessed something of a golden age in international law, although the capstone legislative instruments of the day – the Hague Conventions of 1899 and 1907 – focused primarily on regulating the violence done to combatants rather than civilians. The international reach of the Hague Conventions was a significant departure, even so. This impulse to extend legal regulation beyond national frontiers owed much to the quickening pace of globalization. As states became increasingly interdependent, their need for a functioning and efficient system of international laws to regulate their commercial, cultural and political interactions increased. As with the changing nature of warfare and the importance of mobilization, the First World War’s advent marked a watershed for international law, testing its parameters, applicability and global potential.Footnote ²⁶ The subsequent century has seen an institutionalization of international norms concerning the treatment of combatants and non-combatants, the accelerated development of which is traceable to this first global conflict of the twentieth century. Numerous international conventions regarding civilians, prisoners of war, nuclear and chemical weapons, genocide and other facets of armed conflict have since been signed. With them has come a variety of IOs, including tribunals and specialist monitoring groups. The result is that even states that disregard international norms paradoxically remain attentive to the reach of this increasingly visible arm of the international system. Indeed, the actions of such rule-breakers have set the agenda for recalibrations and extensions of international law. Clearly, then, the civil–military divide cannot be properly understood without an examination of the role of norms, their influence on how conflicts are pursued, and their success or failure in protecting civilians.

This collection’s case studies into the civilianization of war use the interaction of these three factors – the ways in which wars are fought, the mobilization of home fronts and the growing role of international norms – to elucidate the civil–military divide’s constantly shifting form. Before turning to an assessment of each chapter’s contribution, it is worth saying a little more about the three disciplines from which they are drawn. The following chapters bring together case studies written by scholars from international history, political science and international law. Each discipline illuminates important aspects of the civil–military divide, and yet they are rarely brought together, as here, in a sustained collaboration. To fully appreciate the interdisciplinary nature of this enterprise, and the extent to which it is able to become something greater than the sum of these three parts, it is necessary to examine each discipline’s approach to the civil–military divide.

Sharp fluctuations in the civil–military divide suggest a need to revaluate the two views that dominate current scholarly debates over this issue. Each of these interpretative approaches might be loosely defined around two terms derived from political science. The first springs from realist assessments of necessity and the logic behind it. The second is ‘constructivism’. The former emphasizes the importance of states, the competition intrinsic to international systems and the considerations of material power and strategic advantage that determine interstate rivalries. Viewed from that perspective, any normative distinction between civilians and soldiers gains traction only to the extent that it serves the interests of powerful states. The more global a compact is, the greater the agreement between states it requires. Conversely, states may deem it essential to defend their civilians and/or target those of their opponents by threatening to retaliate or otherwise resort to force. While necessity can be used to explain the spectrum of possible state actions, it does not offer any insight into why nations move so quickly and frequently along it. When the conflict involves non-state actors, it also assumes they operate using a similar logic of necessity and, underlying that, rationality.Footnote ²⁷ Yet, in cases of irregular warfare wherein the interconnections between civilian populations and military forces blur the distinctions between the two, the necessity argument becomes harder to sustain, and its predictive power is greatly diminished.

The constructivist perspective stresses the power of ideas relative to the material factors central to realism. The ideas it sees as mattering are related to issues of attitude formation, knowledge construction and consequent cultural outlook. This suggests that it is these more intangible factors that shape the behaviour of individuals, organizations, governments and, ultimately, the international system. While acknowledging the inadequacies of international norms and juridical protections of civilian status, constructivists point to a slowly emerging transnational network of controls, signified by a growing system of international laws, a proliferation of regulatory institutions and NGOs, and critical shifts in global opinion, particularly since 1945. The combined weight of these elements, it is averred, imposes limits on what state and non-state actors can do in situations of conflict. Seen from this vantage point, the civil–military divide not only retains its relevance but is gradually widening as more laws, advocacy groups and other opinion-makers work to uphold it.Footnote ²⁸ This linear perspective is somewhat at odds with the marked variations in the civil–military divide that are outlined in the chapters to come. Ironically, as in the case of strategic realism outlined earlier, the growing interconnectedness that stems from the civilianization of war makes it harder still to predict a progression towards sharper, more rigidly upheld distinctions between combatants and non-combatants, between violence actors and civilians.

Realists focus on states, assessments of material power and foreign interests, and the cost–benefit calculation of actions. Conversely, non-state actors occupy an important place in constructivist thinking, as do the role of ideas and a cost–benefit analysis that is centred on the appropriateness of an action in relation to prevailing norms and the actor’s identity.Footnote ²⁹ The civil–military divide in the context of the civilianization of war falls between these stools. Both the growing presence of a ‘norms discourse’ and the increasingly entangled nature of the civilian and military render calculations and their consequences increasingly difficult and hard to predict.

Added to this is the historical record from which much of this work is drawn. One of the strengths of this collection is that it highlights the important recent work done by international historians on the violence of the last century that has yet to be integrated into the studies of many political scientists. The geographic, thematic and chronological diversity of this international history raises additional challenges by departing from a narrow set of classic accounts of Eurocentric conflicts that have dominated International Relations (IR) to integrate the wars of decolonization that predominated in Asia and the global South.Footnote ³⁰

Judging the influence of norms on decision makers is perhaps nowhere more difficult than in the case of civil conflicts, in which social structures not only are at issue but often break down in the intensity of intra-societal conflicts. While there may be no unifying theory to account for such wars, their increasing frequency suggests that the turn to violence appears instrumentally beneficial, even logical, to many participants.Footnote ³¹ The study of civil wars by Stathis Kalyvas, a specialist in comparative politics, highlights the extraordinary variation in the nature and extent of violence generated by these armed conflicts. Kalyvas’ concentration on the processes of micro-violence that shape the local dynamics of killing offers additional perspectives to those of IR realists and constructivists.Footnote ³² He focuses on the interaction between actors within the conflict: incumbent authorities, insurgents and civilians. Kalyvas’ fundamental preoccupation is with how and why civilians interact with incumbents and insurgents, with the process by which they become enmeshed in the conflict, potentially turning to violence and becoming combatants. His study of civil wars rests on an understanding of micro-level decisions such as how local communities calculate their interest when faced with the alternatives of collaborating with or resisting belligerent forces in highly insecure environments. Framed in this light, the matter of allegiance, often treated as a pre-existing explanatory factor for the violence held to typify civil wars, emerges instead as a more contingent and endogenous phenomenon.Footnote ³³ Micro-histories of this type indicate that there are ‘a host of endogenous mechanisms, whereby allegiances and identities tend to result from the war or are radically transformed by it’. This is one example of a larger point: that what are often seen as the cleavages and disputes that provoke a conflict are not sufficient to explain the motivations of those engaged in violence.Footnote ³⁴ In Kalyvas’ words, ‘the game of record is not the game on the ground’.Footnote ³⁵ Developing an approach that originates in the study of civil wars is apt, because contemporary armed conflicts increasingly exhibit civil war aspects such as paramilitarism, a predominance of irregular forces, and civilian targeting.Footnote ³⁶ Even more important is the ability to apply these insights and approaches to include key aspects of the civilianization of war such as new technologies and those defending international norms. Many of the case studies in this collection do just that (Christopher Goscha, Stacey Hynd, Julius Ruiz).

To this framework we would add three important contributions from IR specialists. The first derives from Robert Jervis’ now classic study of complex systems, which emphasizes that their very complexity necessarily means that actions can have unexpected consequences (a theme addressed in the chapters by Andrew Barros on bombing and John Ferris on naval blockade) and captures an important consequence of the civilianization of war.Footnote ³⁷ This insight is particularly useful when examining the linkage between the military and home fronts. It serves as an expression in IR theory terms of the sometimes unforeseen connections between manifestations of modernity – among them technology and mass production, communications and public opinion, and the greater prominence of IOs and NGOs in international affairs – and the dynamic nature of the civil–military divide over the course of the last century.

The second approach also touches on the question of the unpredictable, in this case the inevitability that intelligence organizations will fail. Developed by political scientists working in security studies, a field that has seen some of the closest collaboration between political scientists and international historians, this approach has also been influenced by work on the role of misperception in IR. Several authors in this collection (Barros, Ferris and Goscha) have integrated intelligence into their analysis to emphasize the importance of perception in understanding belligerent calculations, as well as its ability to reinforce the role of Clausewitzian friction.Footnote ³⁸

The final contribution from this discipline that is reprised by our contributors concerns the self-interested logic of cooperation between belligerents in ensuring the respect of certain norms, and thereby upholding the civil–military divide (see the contributions by Barros, Ferris and Raphaëlle Branche).Footnote ³⁹ Jurists have also studied this question, albeit as part of their examination of compliance with international law. When it comes to understanding the civil–military divide, this literature shares some of the shortcomings of IR theory that were discussed earlier, but it is still of considerable value.Footnote ⁴⁰ The extent to which civilian protection rests on realpolitik calculations rather than the influence of those committed to upholding normative standards of civil–military distinction is a theme integral to several of the chapters here (particularly those by Olivier Barsalou and Frédéric Mégret).

Legal scholars approach the study of international norms and the effectiveness of international law (IL) from a particular specialized training. Given the practical limitations to IL so cruelly exposed by the Second World War, it is not surprising that in the post-1945 period, jurists’ study of their discipline proved susceptible to the influence of the realist perspective. In response, they began exploring new linkages between IL and politics. IL theorists devoted greater attention to the legal process and all that it touched, effectively widening IL’s impact, influence and relevance.Footnote ⁴¹ Naturally, the focus on the process in IL attaches great weight to legal mechanisms and actors. Reflecting this, a seminal study of the history of IL focused primarily on its practitioners.Footnote ⁴² The resultant preoccupation with legal doctrines, actors and institutions, notably lawyers, judges, activists and governments, also promoted a transnational perspective. In similar fashion, the sources examined by IL analysts mirror the legal and procedural events that figure most prominently in the reconfiguration of international law during or after major armed conflicts. There are pitfalls in such an events-led analysis. For example, the burgeoning literature on human rights has a tendency towards finding these rights and their defenders rather than examining their absence.Footnote ⁴³ In the case of IL, then, studies of particular campaigns or cases are, almost invariably, related to the larger functioning of the discipline, via legal actors, authorities, and tribunals, and ultimately the rule of law.

That said, the approach adopted here owes much to the IL literature. Like Kalyvas, Martti Koskenniemi’s influential study, From Apology to Utopia: The Structure of International Legal Argument, has helped define this study’s framework. Koskenniemi reminds us that IL is not an objective, neutral science in the service of a utopian legal order. Nor is it simply an unalloyed instrument of state power, a juridical apology for the fact that might makes right. In Koskenniemi’s view, IL debates need to be seen as a hybrid of these two species; hence the need to employ ‘concepts so that they can be fitted into both patterns, so that they can be seen to avoid the dangers of apologism or utopianism and support both community and autonomy’. For IL to remain relevant, his solution is that ‘the modern lawyer needs to show that the law is simultaneously normative and concrete – that it binds a State regardless of that State’s behaviour, will or interest but that its content can nevertheless be verified by reference to actual State behaviour, will or interest’.Footnote ⁴⁴

These ideas are echoed in David Kennedy’s recent study, Of War and Law, which argues that just as the separation between war and peace has become harder to discern in an era of asymmetric warfare, there has also been an extraordinary intermingling of the legal and the military. Soldiers are increasingly imbued with the law – through their training, through interaction with legal personnel and procedures, and as a factor in operational decisions. War, as Kennedy puts it, has become ‘a legal institution’. As the military increasingly integrates the law into its operations, ‘we are not only allowing a particular language of evaluation. We also allow for that language to substitute for other judgements.’ This language has a ‘capacious’ ability to accommodate conflicting viewpoints and serve opposing strategies, be they of states or humanitarian organizations. Setting legal criteria for the targeting of weapons in order to avoid non-combatant casualties may be exploited to quite contradictory ends. It can serve as an apology for civilians who are then killed by forces in compliance with these requirements. Or it may advance the all too often quixotic desire to end non-combatant losses and suffering. Minimizing civilian casualties can be an effective military strategy, not just a matter of ‘good politics’ or useful propaganda but, in other cases, conferring a fighting advantage to opponents, particularly when they are irregular forces. Political legitimacy, and, with it, a strategic advantage, may be enhanced by being seen to uphold the law and save lives. Or these efforts may confirm for the local population the illegitimacy of those proclaiming to defend civilians. Evaluating the role of norms and IL in the formation of the civil–military divide thus intersects with the analysis adopted here, one that privileges the endogenous aspect of the divide’s evolution, thereby highlighting its fluctuating nature.Footnote ⁴⁵

Relative to the more long-standing attempts to foster greater collaboration between IR and IL, those between specialists in the history of IL and international historians are of younger vintage. Yet, among its many qualities, Koskenniemi’s work has demonstrated how powerful historical examinations of IL history can be an important source of renewal for IL theory. This may help explain the recent and encouraging trend among IL specialists to examine their discipline’s history in light of international history’s core themes and literatures, notably in regard to IOs like the League of Nations and UN.Footnote ⁴⁶

International historians were among the last to arrive at this intersection between state power, the role of normative forces and international institutions. That being said, the post-1945 period saw the field of international history embrace broader perspectives, both thematic and geographical, and enter dialogue with other disciplines, notably IR theory.Footnote ⁴⁷ As with scholars of IL, realism was an important influence, as was the Cold War, both intellectually and in terms of access to archival sources. Trends emerged within this literature, the significance of which became clearer once the discipline engaged with the question of norms, including the modern-day protection of civilians, and thus with colleagues in IR and IL.

The first and most important trend was in the study of armed conflict, especially modern global war. Scholars moved from a narrow high-policy focus on the perspectives of political and military leaders through a number of stages that each widened the analytical framework for the study of war. The First World War is an excellent example of this process. Historians turned their attention towards the lower reaches of the military pyramid, examining the importance and role of junior officers and soldiers at the front, and later their post-war significance as veterans pivotal to processes of cultural demobilization. Studies that followed the peacetime legacies of conflicts raised interesting comparisons with the mobilization and remobilization of belligerent societies. Scholars also began to escape the confines of national history and started to examine these issues from bilateral and multilateral perspectives. Likewise, investigating the war’s financing and economic mobilization also opened the door to the home front and wartime culture, which, in turn, generated more comparative and transnational studies.Footnote ⁴⁸ These works were often grounded in micro-histories that traced the myriad ways in which the conflict changed individuals and groups, be that a detailed examination of the experience of combat at the front or the stresses of daily life behind it.Footnote ⁴⁹ The Second World War also ended in German defeat, but its contours, particularly in terms of ideology and occupation, were very different from those of the First. The resulting loss of civilian life informed several highly influential micro-histories that sought to explain the heightened levels of civil–military violence that punctuated the conflict.Footnote ⁵⁰

Historians of Empire have also been drawn to studying the role of violence in the operation and destruction of colonialism.Footnote ⁵¹ This now burgeoning field, much of which attaches greater significance to the global iniquities between North and South than to the ideological divisions between the Cold War blocs, is essential in explaining the historiographical transformation of the Cold War from a narrowly East–West conflict to a global one.Footnote ⁵² With this sharper focus on inequalities and sources of discrimination as critical factors in international politics and transnational mobilization,Footnote ⁵³ imperial historians have also entered the debates over international norms, including the troubled history of human rights.Footnote ⁵⁴

Bringing together these historiographies, the theoretical and methodological strengths of each field are applied across a wide series of case studies to indicate how civil–military divides evolved. Our objective is to examine this endogenous process, one that is central to coming to a better understanding of the dynamism that the distinction between civilian and military has repeatedly demonstrated. The case studies locate the civil–military divide in the growing civilianization of war.

Each of the study’s three sections reprises one of the key factors at the heart of this process: the changing nature of war, the role of mobilization and the ‘home front’, and the ‘traction’ of international norms. The opening section focuses on the changing nature of war by examining those who actually fight. The first part of that section deals with the 1914–45 period, an era marked by a redefinition of the character of war. John Ferris examines how IL became an increasingly important aspect of British naval strategy, as demonstrated by its connection to the 1915 Allied strategy of naval blockade. He shows how, in the hands of British authorities, IL proved extremely malleable, a quality that helps explain both its growing importance and its unintended consequences. Julius Riuz spotlights Republican violence during the Spanish Civil war. He examines how Republican fighters, like their Francoist opponents, became complicit in a collapsing of the civil–military divide. Jean Lévesque looks at an extreme case of civil society being transformed into combatant form: the Soviet People’s militia of 1941. He underscores how even in this extraordinary situation the divide diminished but did not disappear.

The second section focuses on the post-1945 years in which the Cold War and decolonization wrought fundamental changes in the nature of war. Christopher Goscha explores the Democratic Republic of Vietnam’s unprecedented use of men, women and children in its armed struggles in the first decade after 1945, a mobilization with seismic consequences for the civil–military divide within Vietnamese society. Raphaëlle Branche approaches the civil–military divide from the perspective of a discrete military category: prisoners of war (POWs). Focusing on the Algerian War of Independence, a decolonization conflict whose warring parties disregarded the combatant rights of their opponents, she demonstrates the acute insecurities that resulted for those faced with capture. Christian Gerlach revisits the targeting of particular civilian social groups during Bangladesh’s bitter secession from Pakistan in 1971 while also offering important methodological lessons for the study of what he terms ‘extremely violent societies’. Stacey Hynd shares Branche’s and Gerlach’s concern with distinct social categories as subjects and objects of collective violence. Her contribution on child soldiers in Africa shows how children present a uniquely difficult test of the civil–military distinction, one that is complicated by clashes between Western and non-Western conceptions of childhood and legal responsibility.

The collection’s second section uses the development of aerial bombardment, sustained campaigns of strategic bombing in particular, to trace the civilianization of war from the military to the home front. Using Britain’s Royal Air Force (RAF) as his exemplar, Andrew Barros examines a case of overestimating the ability of aerial bombardment to close the civil–military divide in his account of the interwar debates over its use and regulation. In doing so, he underscores how the increasingly complex nature of bombing made these types of calculations progressively more difficult. Victor Bissonnette’s chapter also studies the growing importance of science and technology in bombing. He examines the Operations Research Section of the RAF’s Bomber Command during the Second World War, and the extent to which civilian losses figured in their scientific calculations. Alex Downes focuses on a post-1945 bombing campaign – during the Korean War – one that produced an extraordinary casualty toll among civilians. As he demonstrates, it, too, required a critical shift in strategic thinking about civilian status, which led from limited American engagement to a campaign of devastating destructive power. Finally, Chris Fuller connects the history of bombing with present-day concerns in his study of drones. He highlights the new ways in which this technology challenges the civil–military distinction.

The collection’s final section investigates the third key factor in the creation of the civil–military divide: international norms in the form of juridical protections for civilians in war. Andrew Barros provides a rare study of an effort to eliminate the civil–military divide by turning everyone into civilians. His examination of Nobel Peace laureate René Cassin and the creation of the United Nations Educational, Scientific and Cultural Organization (UNESCO) is one example of the growing support for international norms that emerged in the wake of the Second World War. Olivier Barsalou offers an alternative perspective on this ‘human rights surge’ by illustrating the extent of US direction in the construction of a new IL regime.Footnote ⁵⁵ He assesses the extent to which American foreign policy shaped the UN’s Human Rights Commission, one consequence of which was that the civil–military distinction became stymied by overarching US strategic calculations. Martin Thomas studies decolonization’s spillover within the UN as reflected in the fierce debates that systematic abuses of civilians triggered inside the organization, particularly during the final phase of European colonial collapse. Frédéric Mégret revisits recent cases in which the pressing need for civilian protection has catalysed UN-sanctioned international interventions. He argues that UN peacekeeping missions are increasingly centred on protecting civilians, itself a reflection of and contribution to the ‘civilianization of war’. But, as Mégret points out, little thought has been given to the ramifications, resources and political demands that come with this shift..

The book’s three sections, taken together, thus offer the reader multiple perspectives and cases as varied as the phenomenon they are studying. They examine interactions between the changing nature of war, the mobilization of combatant societies, and IL and norms, to demonstrate the dynamism of the civil–military divide in the context of the last century’s civilianization of warfare. In doing so, the collection, we hope, makes some contribution to advancing civilian protections.