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The 'Legal Pluriverse' Surrounding Multinational Military Operations$

Robin Geiß and Heike Krieger

Print publication date: 2019

Print ISBN-13: 9780198842965

Published to Oxford Scholarship Online: February 2020

DOI: 10.1093/oso/9780198842965.001.0001

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The History of Multinational Military Operations and Contemporary Legal Challenges

(p.1) Introduction
The 'Legal Pluriverse' Surrounding Multinational Military Operations

Robin Geiß

Heike Krieger

Henning Lahmann

Oxford University Press

Abstract and Keywords

An introduction to the aims of The ‘Legal Pluriverse’ Surrounding Multinational Military Operations, defining the key terms to be used within the book, particularly ‘pluriverse’, a term which is used to describe the multiplicity of rules that apply to and regulate contemporary multinational missions and the diversity of actors involved. This chapter briefly outlines the five main parts of the book and the legal problems that are dealt with by the contributing authors in their individual chapters, providing the necessary background for the book as a whole to take stock of this legal pluriverse and help to make sense of it in order to gradually move towards a more coherent regime.

Keywords:   multinational military operations, peace enforcement, peacekeeping, laws of armed conflict, United Nations, coalition warfare, international human rights, status-of-forces agreements, state responsibility

1. Concept and Challenges

‘There is only one thing worse than fighting with allies, and that is fighting without them.’1 Ascribed to Winston Churchill, who was reflecting on the fraught and complicated Alliance that nevertheless managed to liberate Europe from Nazi Germany, the famous quote might have turned into a cliché by now. Yet Churchill’s sentiment still rings true decades later. Today, when states decide to deploy their militaries, they usually do so in concert with other states. Multinational military operations have become the default mode for administering global security governance in the twenty-first century. As one author has observed, they are so common now that they might well be the only ones most states have conducted at all in recent years.2

At the same time—as Churchill’s witticism illustrates—going to combat jointly with another sovereign’s forces is anything but a novelty.3 Indeed, as far back as in ancient Greece, different communities with not always entirely aligned interests, and with sometimes vastly uneven powers, have come together in order to achieve a common purpose by military means. But it perhaps has never made more sense than today: in an ever-shifting global threat environment, the reasons for multinational military operations are manifold and range from aiming to increase efficiency and cost-effectiveness of missions to augmenting their legitimacy.4 The more matters of transnational security have become a multilateral concern since the end of the Second World War, the more military operations have become multinational. Accordingly, the United Nations or regional organizations often play a crucial role, not only mandating missions but frequently also assuming command and control.5 The trend towards ever more military integration has been (p.2) conspicuous at least since the end of the Cold War, with some organizations now even commencing to properly institutionalize the multinational approach.6

The more complex, multifunctional, multidimensional, and protection-oriented contemporary multinational military operations become, and the more actors are involved, the more intricate the surrounding legal questions inevitably become as well. Whether operating under the command of a single hegemonic state, or a regional or international organization, a multitude of partly distinct, partly overlapping legal regimes apply to each mission. These regimes stem from various sources: bi- and multilateral international agreements or customary international law; but also soft law has an important role to play, be it through national or multinational codes of conduct, best-practice recommendations, or mission-specific rules of engagement.

Against this backdrop, the present book aims to conceptualize and rationalize The ‘Legal Pluriverse’ Surrounding Multinational Military Operations. This term is used to describe the multiplicity of rules that apply to and regulate contemporary multinational missions and the diversity of actors involved. The book intends to systematically compile and take stock of the various legal regimes which make up this pluriverse, to assess how these rules interact, and to expose norm conflicts, areas of legal uncertainty, or protective loopholes. Taken together, the book’s individual contributions identify and evaluate approaches to better streamline the different applicable legal frameworks with a view to enhancing cooperation and thereby to ensure the long-term success of multinational military operations.

As its premise, The ‘Legal Pluriverse’ Surrounding Multinational Military Operations takes up the trend towards ever-more robust mandates, not least within the United Nations framework.7 Thus, without failing to acknowledge that holistic approaches are necessary in order to achieve and secure peace and security on the international level, as the military alone is inherently incapable of solving any conflict, this book nevertheless focuses on military operations.

(p.3) 1.1 Multinational military operations: a preliminary approximation

There has not emerged a clear and universally agreed upon legal or political definition of the concept of multinational military operations to date. For the purpose of this book, it will be understood in a broad sense as any mission involving armed forces relying on contributions of a number of states and other actors such as international organizations. Those operations typically, but by no means exclusively, take place in zones of armed conflict and in areas of limited statehood with deficient or partially absent governance structures. One significant characteristic of such areas is a prevalence of organized crime and other, similarly destabilizing, factors. As a consequence, multinational military operations frequently find themselves in a situation in which they do not just have to fulfil more traditional military functions, but at the same time—often even more importantly—engage in policing and other governance functions in the territory that they control or in which they operate.

Often comprising a considerable range of troop-contributing states, the objectives of such military operations are just as varied as their mandates, and regularly multidimensional. Depending on the context, they engage in conflict management, the protection of civilians, disarmament and demobilization efforts in the aftermath of internal conflict; they conduct specific law enforcement missions or attempt to implement the rule of law8 or reform and train the security sector.9 Multinational forces can be found in transnational counter-terrorism endeavours10 as well as in post-conflict situations11 or major disaster relief operations.12 And not only the diversity of actors on the operation’s part is crucial to reckon with. Just as significant is the range of stakeholders on the target area’s side that interact, cooperate, and engage with the foreign troops such as regional states, local authorities, or a number of different non-state actors ranging from armed groups to humanitarian NGOs. All this shows that while there are certain characteristics that all multinational military operations have in common, the differences are just as significant and thus need to be considered by any overarching treatment of the topic.

As any military commander will readily attest to, multinational operations can easily be more time-consuming, cumbersome, and overall more limiting than (p.4) pursuing sensitive missions with only one’s own capacities.13 This observation, of course, begs the question why this form of military engagement became so prevalent in the twentieth century that it can only be described as being the norm at the outset of the twenty-first century. Historically, the most important reason for setting up multinational operations was the aggregation of military capabilities. After the French Empire under Napoleon had conquered large parts of the European continent, the opposing states concluded that the only chance they had to beat the French troops was to build an uneasy coalition and thus combine their respective military powers.14 But this rationale does not always hold up today. Otherwise a powerful nation such as the United States, with a military capacity that eclipses that of every other state, would virtually never have a true incentive to build a coalition in order to pursue its geostrategic goals.15 However, as could be witnessed during the prelude to the internationally contentious war in Iraq against Saddam Hussein’s regime in 2003, the United States made a serious effort to convince other nations to join in. The goal, of course, was to gain legitimacy, a motive especially consequential in an international system that has outlawed war as a legitimate means of politics.16

For other states, however, the burden and cost sharing argument continues to be an important factor when deciding whether to participate in a multinational operation. Further advantages such as facilitated access to resources, intelligence, and other strategic gains come up as well.17 Still, it is the question of legitimacy that most pointedly reveals why most nations and internationally mandated operations make an attempt to gather allies in order to achieve a certain political goal by means of military might:18 when no legitimacy is expected or sought, the issue of joint military missions appears to become less urgent. An example of a state that decided to act on its own is the Russian Federation in its armed conflict with Georgia in 2008. The Russian Federation had apparently concluded that its own strength would be sufficient to prevail whereas the legal justification for intervention on behalf of Georgia’s separatist regions Abkhazia and South Ossetia remained doubtful.19 A comparable situation occurred in 2014 with regard to the (p.5) Russian Federation’s intervention in Eastern Ukraine. In both cases, Russia had decided not to pursue coalition warfare. Thus, if increased legitimacy is not expected and burden sharing is considered unnecessary to achieve their goals, states are apparently still willing to proceed on their own.

1.2 Legal justifications and mandates

A broad spectrum of mandates is possible when it comes to establishing multinational military operations, relying on virtually all conceivable legal justifications. Most strikingly, the UN Charter itself envisages joint military engagements, explicitly providing for the collective use of force in situations that involve a threat to international peace and security,20 and acknowledging the important role of regional arrangements in Chapter VIII.

Some forms of collective engagement involve armed contingents without comprising a clear military component, for instance missions with the purpose of monitoring a ceasefire agreement in a post-conflict situation or capacity building missions. Examples include the UN verification mission in Colombia in the aftermath of the country’s decades-long civil war21 or the European Union Training Mission in Mali (EUTM Mali).22 Such operations are not the focus of this book. Instead, the contributions zoom in on operations that were mandated in such a way as to at least imply the authorization of a resort to force, such as in Afghanistan, the Democratic Republic of the Congo, Libya, Somalia, or Mali.

Concerning possible justifications for such missions, a wide array of legal bases is conceivable. Over the course of the past decade, multinational military operations have often operated with UN Security Council authorization under Chapter VII of the Charter, for example the United Nations Multidimensional Integrated Stabilization Mission in the Central African Republic (MINUSCA), mainly involving troops from other African countries;23 or arguably the 2011 intervention during the uprising in Libya, claiming to enforce UN Security Council Resolution 1973.24 It was led by NATO and principally conducted by France and the United Kingdom but involved in total the forces of seventeen states, including four non-NATO nations.25

(p.6) In other instances, states have acted in concert upon invitation of a beleaguered government, as for example concerning Operation Astute in Timor-Leste from 2006 to 2013, led by Australia with considerable contributions from New Zealand, Portugal, and Malaysia;26 in Mali in early 2012, when France and a few other European states cooperated with the Economic Community of West African States (ECOWAS) in order to fight different Islamist factions in the northern part of the state,27 or against the Islamic State of Iraq and the Levant (ISIL) in Iraq.28 Regional organizations have intervened in member states in the course of internal armed conflict or other serious turmoil, as for example the African Union in Darfur from 2004 (the African Union Mission in Sudan (AMIS), later dissolved in the United Nations/African Union Hybrid Operation in Darfur (UNAMID)),29 or ECOWAS in the Gambia since the occurrence of a post-election insurgency and the breakdown of public order in January 2017 (Operation Restore Democracy or ECOMIG).30

As for further legal justifications for more recent multinational military operations, partaking states have invoked the right to collective self-defence pursuant to Article 51 of the UN Charter, as for instance regarding the intervention in Afghanistan against the Taliban regime in the aftermath of the terrorist attacks of September 11, 2001;31 or, more recently, in the case of the US-led coalition strikes against ISIL in Syria, an operation that was justified as a collective self-defence action on behalf of Iraq.32 Humanitarian grounds in accordance with the ‘Responsibility to Protect’ doctrine have also been cited on several occasions, as by some participants in the case of the multinational intervention in Libya in 2011,33 but also in the multinational fight against ISIL in Iraq and Syria.34

(p.7) 1.3 Forms of cooperation

Just as multinational military operations may be conducted under many different mandates relying on varying legal foundations, the possible forms of cooperation between the troop-contributing states and other participating actors are just as manifold. To a certain degree, it is often the mandate that determines the organizational modalities of the mission. What is more, the legal justifications invoked for intervening may change over time, so that different mandates apply to different phases of one and the same multinational mission, correspondingly affecting the modes of cooperation between the individual forces.35

While regional organizations assuming a leading role is continuing to become more common, a considerable number of recent multinational missions have operated within the framework of the United Nations. But here, too, vastly different forms of implementation exist. On the one hand, direct UN command is the standard model for traditional peacekeeping missions. Established as subsidiary bodies of the United Nation’s principal organs, states allocate their troops to the peacekeeping mission by way of contractual agreements.36 Examples are the United Nations Operation in Côte d’Ivoire,37 the United Nations Stabilisation Mission in Haiti,38 or the United Nations Interim Administration Mission in Kosovo.39

If the UN Security Council merely provides a mandate to a multinational operation by authorizing the use of military means with a Chapter VII resolution, on the other hand, the subsequent mission will usually not act within the UN institutional framework. In these cases, the actors that actually carry out the peace enforcement mission, that is either a coalition of states or a regional organization such as the African Union or NATO, retain all command responsibilities.40 A long-running instance is the ongoing African Union Mission to Somalia,41 which was established in 2007 by Security Council Resolution 1744.42 Operating under AU command, six member states have provided troops that are each responsible for different geographic sectors of Somalia. Another significant example for this variant was the International Security Assistance Force in Afghanistan between 2001 and 2014,43 a NATO-led operation authorized by Security Council Resolution 1386.44

(p.8) A third modality are hybrid or co-led operations that are based on command structures involving both the United Nations and military representatives of a regional organization, such as for example in the already mentioned UNAMID.45

On a more granular, operational level, more noteworthy distinctions can be observed. The actual cooperation between states’ military organizations in multinational operations will always be tailored to meet the specific circumstances of the respective mission. In some cases, partnered states will in fact combine their forces on the battlefield in joint operations, as during the first months of the 2003 invasion of Iraq by the so-called ‘Coalition of the Willing’, which involved fighting troops from the United States and the United Kingdom as well as Australia and Poland. Other states provided military contingents without taking an active role in combat, mostly for the purpose of post-invasion stabilization of Iraq.46 In the Multinational Joint Task Force (MNJTF) Nigeria, Cameroon, Chad, and Niger combined their forces in order to fight the terrorist organization Boko Haram. MNJTF has been acting under the auspices of the Lake Chad Basin Commission (LCBC) since March 1994 and has been endorsed by the African Union Peace and Security Council.47 When several Arab states started intervening in the civil war in Yemen in 2015 after a joint statement by the Gulf Cooperation Council, the Saudi-led coalition comprised fighter jets from Egypt, Morocco, Jordan, Sudan, Kuwait, the United Arab Emirates, Qatar, and Bahrain.48

In other instances, one or a number of states are merely providing logistical support while the forces of one or more allied nations conduct the actual military operations. This approach was followed during Opération Serval. The military operation against Islamic militant groups in northern Mali was principally conducted by France but relied on military transport capabilities by several cooperating states including the United States, the United Kingdom, Canada, and Germany.49

The above cases shall merely serve as a rough overview in order to illustrate the spectrum of contemporary multinational military operations, without aiming to provide a full picture of all possible variations. This preliminary mapping shows a (p.9) landscape of possible missions that is both fragmented and fluid. The modalities of each individual case depend on factors such as mandate, operational design, the capabilities of the cooperating states, or their political or strategic willingness to commit to a certain degree of involvement. As no two missions are ever exactly alike, the notion of ‘multinational military operations’ that underlies the present book should be considered an overarching, intentionally loose and only minimally defined concept. Such a broad approach is necessary, as the great variety that can be observed indicates legal complexity, the analysis of which is the purpose of the present selection of contributions on the topic. This complexity, framed as the eponymous ‘legal pluriverse’, will briefly be outlined below after a cursory look at the history of multinational military operations.

2. Multinational Military Operations over Time

2.1 Historic development

Military coalitions have been a defining characteristic of much of human history all the way back to antiquity. That being said, what one considers the starting point of the history of multinational military operations strongly depends on one’s view as regards the requirements of actual military cooperation on the ground. Already in ancient Greek mythology, the Trojan War was told as a story of a campaign of an alliance of Greek communities against a coalition of their Trojan adversaries. A few centuries later, the Greek city states built various alliances during the wars against the invading troops of the Persian Empire—which in itself should be considered an assemblage of different nations rather than a coherent ‘nation’50—with wavering endurance and success, culminating in the devastating defeat at the pass of Thermopylae in the late summer of 480 BC.51

More to the point, coalition warfare gained traction after the middle ages at the outset of the modern period.52 However, although a number of European powers were heavily involved in the Thirty Years War, the operations mostly amounted to battles of one entity against another. If collaborations existed at all, they were very limited in time and purpose. Therefore, historians have suggested that it was not until after the establishment of the Westphalian system in 1648 that coalition warfare in the modern sense came into being. As a starting point for the novel (p.10) modus operandi of warfare, one may look at the Dutch War in the second half of the seventeenth century, when France’s Louis XIV, Britain’s Charles II, Münster, and Cologne formed a coalition against the Dutch Republic, which was then assisted by the Habsburg Monarchy, Brandenburg-Prussia, and Spain.53 A few years later, a pan-European alliance led by King John III Sobieski of Poland broke the Ottoman Empire’s siege of Vienna.54

The already mentioned wars against Napoleon at the beginning of the nineteenth century serve as another cornerstone for the history of multinational operations. Considering the emerging nationalist currents in the decades after the French Revolution in 1789, they might even count as the first ones to justify the notion ‘multinational’. Between 1803 and 1815, seven military coalitions in total were formed in order to eventually defeat the French Empire.55 Still, it has been pointed out that frequent and severe disagreements between the partnered states long prevented success against Napoleon, which even led him to assert that he preferred to lead war against coalitions.56 Even at the Battle of Waterloo in 1815, despite fighting as an alliance, Prussia’s General Blücher and Britain’s Wellington acted separately rather than jointly, so that both partners could assert their own victory against the French army.57

Another important event in the history of multinational military operations was the Crimean War in the middle of the century, in which a coalition mainly consisting of the Ottoman, British, and French Empires and the Kingdom of Sardinia fought against the Russian Empire, with contingents from a few smaller European powers on both sides.58 Moreover, the conflict is noteworthy for serving as the theatre for one of the first deliberate combined forces campaigns as an integral part of a multinational expedition.59

Over the course of the nineteenth century, the zenith of the colonial age saw a number of armed conflicts involving military coalitions. Those sometimes engaged in wars between settler-colonial states and metropolitan colonial powers as in the Second Boer War from 1899 and 1902. The war was conducted between the Orange Free State and the South African Republic on the one side, and the British Empire on the other. Britain fought in alliance with troops from some of its colonial subjects such as Australia, New Zealand, India, and Ceylon, but also with a significant contribution by recently independent Canada.60 Other joint campaigns (p.11) in colonial contexts are even more historically fraught, as for instance the highly problematic suppression of the Boxer Rebellion in northern China between 1899 and 1901, conducted by an alliance of no fewer than eight colonial powers against the insurgent Yìhéquán and the declining Qing Dynasty’s forces.61

While the United States remained a decidedly reluctant co-belligerent, not entering the First World War before 1917,62 the war proved to be a test case for coalitions between Europe’s main powers. On the side of the western alliance, early German advances made concerted action necessary, resulting in the foundation of the Supreme War Council in 1917 which comprised military representatives from the United Kingdom, France, Italy, and the United States.63 In the view of prevalent scholarship, adopting a united and centralized framework for the military campaign ultimately assured victory despite differences among the allies.64 During the Second World War, the efforts by the leaders of the United Kingdom, the Soviet Union, and the United States to come together in the Grand Alliance after 1941—despite virtually irreconcilable ideological disparities—proved crucial in order to defeat the Axis Powers. Britain and the United States went as far as to fully integrate their respective armed forces in the Combined Chiefs of Staff (CCS) in Washington DC in January of 1942, the body through which the allies subsequently jointly made all relevant decisions for the war.65

In contrast to the two World Wars, some of the most noteworthy armed conflicts of the Cold War period were characterized by states conducting military campaigns largely on their own despite being members of collective defence organizations. Some of these armed conflicts fall into the category of ideological proxy wars along the East/West divide, such as the Soviet Union’s intervention into Afghanistan in 1979.66 Others marked the end of the colonial era, when European powers were confronted with independence wars in their overseas territories. The Algerian war from 1954 until 1962 may serve as the most striking example in this regard.67 The war in Vietnam, by contrast, while mostly remembered as principally a solo campaign by the United States, is an important case in point for the legitimizing function of coalition building. Being acutely aware of the shaky moral, legal, (p.12) and political grounds on which the decision to intervene on behalf of the Saigon government stood, the decision-makers in Washington DC made a serious effort to convince allied nations in the region, mainly Australia and New Zealand, to participate in the conduct of hostilities in Vietnam, chiefly out of political rather than military considerations.68

Also during the post-Second World War period, a series of armed conflicts in the Middle East saw an effectively solitary Israel threatened and attacked by a number of Arab coalitions,69 starting on the day after Israel’s declaration of independence in May 1948.70 Within the context of multinational military operations, these conflicts are notable for the repeated, decisively premature dissolution of the wartime coalitions between the Arab nations despite a similar cultural and religious background and the shared goal of defeating the Israeli state.71

Since the end of the Cold War and the bipolar world order, multinational military operations have vastly increased not only in number, but also in overall geo-political significance. A first test of the new multilateral reality came in 1991 with Operation Desert Storm, the coalition campaign to end Iraq’s occupation of Kuwait.72 At the same time, however, it laid bare frictions among the involved parties, in particular the five permanent members of the UN Security Council which had mandated the Chapter VII operation with Resolution 678.73 While the United States advocated a further invasion of Iraq with the aim of removing Saddam Hussein, the Soviet Union and France, in accordance with the Arab members of the warring coalition, were strongly in favour of sticking to the more limited objectives as stated in the resolution. Ultimately, the United States did not follow through.74 Over the course of the 1990s, the armed conflicts triggered by the dissolution of the Socialist Federal Republic of Yugoslavia gave rise to increasingly institutionalized, long-term engagements of multinational forces. These forces were led by international organizations such as the United Nations or NATO and endowed with progressively robust mandates. Still, failures and shortcomings could not be prevented75—most momentously the United Nations Protection Force’s (UNPROFOR) inaptitude to prevent the genocide in the Bosnian town of (p.13) Srebrenica in 1995, which was traced back to a number of factors, inter alia the lack of a clear mandate and a lack of coordination between political leaders and military commanders.76

The terrorist attacks of September 11, 2001 turned out to become yet another watershed in the evolution of multinational military operations. Not only did NATO for the first time in the alliance’s history invoke Article 5 of the North Atlantic Treaty, which determines that an attack against one member is considered an attack against all,77 for the subsequent intervention in Afghanistan against the Taliban regime, the United States could count on the support of a wide-ranging coalition of states, not only consisting of NATO members. After the UN Security Council had established the International Security Assistance Force (ISAF) in order to assist the transition towards a democratic government in Kabul, no fewer than forty-three states were involved in the operation.78 However, for the invasion of Iraq in 2003 which lacked UN authorization, the United States were compelled to form a ‘Coalition of the Willing’ of concurring states. It eventually comprised troops from the United Kingdom, Australia, and Poland, with other states joining after the initial phase of armed conflict in order to provide assistance during the transition.79 Just like a few decades earlier in Vietnam, building a coalition mainly served the purpose of enhancing legitimacy for a legally and politically fraught endeavour.

The rich and well-documented history of peacekeeping and peace enforcement operations under the auspices of the United Nations and regional organizations, finally, calls for a treatment of its own.80 It represents a prevalent yet clearly distinct category of multinational military operations. Arguably having their beginnings as early as in the 1920s in the form of delimitation commissions to redraw certain frontiers in Europe in the aftermath of the First World War81 these missions were initially mostly confined to small-scale observer missions.82 Over time peacekeeping and peace enforcement missions have become a staple of international (p.14) security governance. In particular after the end of the Cold War, they not only vastly increased in number, as already mentioned, but also became much broader in scope, with a growing focus on the protection of civilians in armed conflicts and post-conflict stabilization.83 Since 1948, there have been seventy-one peacekeeping operations within the UN framework, with 124 states contributing uniformed personnel.84 The most troops have been sent by India, Bangladesh, and Pakistan.85

Since the 1990s, regional organizations have increasingly taken on a more prominent role in peacekeeping and peace enforcement, more often than not in concert with the United Nations.86 The three organizations that stand out are the African Union, the European Union, and NATO. In 2003, the African Union, which superseded the Organisation of African Unity in 2002, conceived its Peace and Security Council (PSC AU), whose mission statement is to actively promote stability on the continent. That same year, it oversaw the first operation, the African Mission in Burundi (AMIB),87 made up of forces from South Africa, Ethiopia, and Mozambique, before the United Nations assumed primary operational responsibility in 2004.88 Since then, missions have been conducted in Sudan (AMIS, 2004–06),89 Comoros (AMISEC, 2006; MAES, 2007–08),90 Mali (AFISMA, 2013; subsequently transformed into the already mentioned UN-led MINUSMA),91 and the Central African Republic (MISCA, 2013–14; subsequently transformed into UN-led MINUSCA).92

The Amsterdam Treaty, concluded in 1999, legally enabled the European Union to conduct multinational operations on the basis of its Common Foreign and Security Policy (CFSP) and the European Security and Defence Policy (ESDP), the latter of which has since been transformed into the Common Security and Defence Policy (CSDP). Since the EU started conducting military and civilian (p.15) crisis management operations in 2003, roughly thirty such missions have been undertaken.93

As already hinted at, NATO started transforming from the mutual defence arrangement that it had been conceived of during the Cold War into a more multi-purpose collective security organization. Taking on more diverse tasks, the alliance conducted its first multinational operation with the aim of keeping and enforcing peace in Bosnia and Herzegovina in 1995 (Implementation Force, IFOR), followed a year later by the Stabilisation Force (SFOR).94 Conduct in former Yugoslavia (FRY) was completed with the 1999 KFOR mission in Kosovo, which was deployed in the aftermath of NATO’s air campaign against the FRY.95 Since June 2007, the alliance has been assisting the AU Mission in Somalia (AMISOM), providing airlift duties.96

2.2 Trends and changes concerning the nature of multinational operations

The historic development of multinational military operations over the course of the last centuries has shown a clear evolution from ad hoc alliances, formed for rather limited purposes in the context of military campaigns or certain theatres of conflict, to institutionalized and multi-purpose tools of international security governance in the post-Cold War global order that often run over the course of a number of years.

For a number of years after 1990, the most important factor for this observed change was the increased role of international and regional organizations as collective security arrangements in not only mandating, but more and more also leading and conducting multinational military operations. Save a few prominent exceptions, military missions towards the end of the twentieth century and at the beginning of the twenty-first were performed within the framework of larger associations of states, more often than not on the basis of a mandate issued by an international organization. This trend both boosted legitimacy of such operations in the eyes of the global constituency and helped—at least to some degree—to more evenly distribute their costs and burdens.97 At the same time, a growing perception of the global institutionalized system as an administrator of world peace and security made military solutions more likely, ever so often treating the combined states’ armed forces as a globally deployable, transnational police force.98 However, (p.16) it bears mentioning that over the past couple of years, the mentioned trend has slowly started to reverse. Marking yet another shift, this time diverging from internationally mandated missions, more states have started to conduct military operations unilaterally and within the framework of ad hoc coalitions with other willing allies again. In legal terms, those states have been more likely to invoke the right to self-defence or the doctrine of humanitarian intervention rather than to rely on a Security Council authorization—as seen above in the cases of Iraq, Syria, or Eastern Ukraine.

This redefined function of multinational missions has become particularly apparent in the so-called global ‘war on terrorism’, a genuinely borderless conflict involving a great number of states in varying constellations, engaged in different missions, operating with shifting mandates, and embedded in various institutional frameworks. One noteworthy feature of most of these missions is their clear military mandate. At the same time, the objectives vary, ranging from administering post-conflict transition in Afghanistan to suppression of piracy off the East African coast and on the Somalian mainland,99 or active counter-terrorism operations against ISIL in Syria and Iraq.100 And even though the so-called ‘war on terrorism’ after September 11, 2001 has mostly been performed under leadership of the United States, there is a general understanding that pursuing a broad international alliance of states is indispensable if any kind of long-term successful outcome is to be achieved.101

Regional organizations’ more recent shift from constituting collective defence alliances to functioning as collective security arrangements has entailed considering ever more global issues as being matters of security. This shift broadened not only the organizations’ operative scope but crucially also increased the number of situations which are deemed fit to be treated with a combination of multinational armed forces, police, and civilian administrators.102 At the same time, it has been observed that multilateralism has made it easier for states to commit troops or other officials to such operations. Heightened legitimization, in combination with functional control by an international organization, in many states fulfils the high legal requirements set up by their constitutional arrangements and leads to more acceptance by the troop-sending states’ populations.103

(p.17) This trend has been expedited by further efforts to properly institutionalize multinational operations. As mentioned, the United Nations now routinely works in concert with other international organizations. As for regional consolidation, it is noteworthy to point to recent attempts by the African Union to set up permanent standby brigades with military, police, and civilian components for five defined regions on the continent. Two of those have been operational since the autumn of 2016.104

3. Contemporary Multinational Military Operations

3.1 Stocktaking

Most current multinational military operations have been mentioned in the sections above. At the time of writing, there are fourteen active UN peacekeeping operations. Seven of those are set on the African continent, two in Europe, one in the Caribbean, one in South Asia, and three in the Middle East.105 UNAMID, the UN mission in Darfur, is conducted jointly with the African Union. The other ongoing African Union operation is AMISOM, deployed to Somalia since 2007.

Outside the peacekeeping context, multinational missions of note are—with or without UN mandate—the Saudi-led intervention in Yemen and the multiforce conduct against ISIL in Iraq and Syria, which consists both of an air campaign by various nations and special forces operations on the ground. Operation Atalanta, the EU-led mission to fight piracy in the Western Indian Ocean that includes capacities from a couple of non-EU states, has been active since 2008.106

3.2 Legal questions and challenges

A look at the list of current multinational military operations, noting their phenotypical differences, leads to the issue of the legal questions and other challenges connected to them today. As a direct result of the mentioned diversity of mandates, setups, and general operational activities, multinational military operations are subject to a multitude of partly distinct, partly overlapping legal regimes. In this context, it has already been alluded to that necessarily, a mission’s underlying mandate and legal justification to some degree determines the relevant applicable rules. Yet as there is no ‘standard model’ for multinational operations given the spectrum of possible engagements and modalities, few universal norms can be derived in (p.18) the abstract. While for a field as established as peace operations under the auspices of the United Nations it is instructive to compile some kind of rulebook of recurring legal standards,107 for multinational military operations more generally it seems at least equally important to approach the topic by way of focusing on the different relevant subject matters. Those include, inter alia, the law governing the jus ad bellum, international humanitarian law, international human rights law,108 international environmental law, the law of the sea, the law of state jurisdiction, state immunity, or the law governing state responsibility.109 That is the approach of the present book.

Of course, not all challenges are matters of international—or indeed national110—law. Quite the contrary: many of the peculiar intricacies concerning the interoperability of the different parts of recent or current multinational missions can be explained by looking at cultural and related discrepancies,111 or problems caused by the sheer dimension of the undertaking. The more states contribute to a single operation, the more obvious the drawbacks of collaboration become. To be mentioned here are differences in strategic or cultural leadership approaches, diverging ethical guidelines that are sometimes heavily informed by varying religious backgrounds,112 or different cultural attitudes towards casualties among one’s own troops.113 To name an example, the participation of women soldiers in multinational operations, in particular in commanding ranks, might trigger complications with contingents from nations whose cultures are not accustomed to this practice, or perhaps even reject it outright on the grounds of cultural or religious principle.114 A crucial difference with potentially serious ramifications in the field has been observed between troops from individualist and collectivist cultures as regards the communication process. While armed forces members from individualist societies tend to communicate more directly, groups with a collectivist cultural approach are inclined ‘to deliver inborn, ambiguous, context-sensitive messages’ that may be hard to fully grasp by individuals from outside such groups.115 There are also more practical downsides such as logistical challenges, capability or training deficiencies among some of the involved actors as compared (p.19) to their partners. Probably above all else, there are the pitfalls of speaking different languages that invariably need to be taken into account when planning the operation or individual tasks in the operation’s course.116 In fact, the language problem is most often cited as one of the principal causes of inefficiency and shortcomings of multinational military operations.117

What is more, even if states agree to engage in a joint military mission, that does not necessarily mean that their strategic political interests or long-term goals are aligned. Individual states frequently arrive with vastly differing understandings of what the operation is supposed to achieve. More to the point, several scholars have argued that an actual unity of purpose, one that is beneficial to the functioning of the coalition, requires a grave and imminent threat to the involved actors. Only in such cases, as for instance in the campaign to defeat Napoleon, can the overwhelming pressure of having to collaborate for success overcome the negative aspects of cooperation.118

Where such an incentive is missing, a clear and agreed-upon legal framework can in fact not only constrain the actors but may rather serve as a stable ground from which the mission is then able to achieve its objectives. By circumscribing each contributing military’s possible conduct, the applicable body of law can conceal existing strategic or cultural differences and thus contribute to a multinational military operation’s ultimate success. This consideration only further shows why it is crucial to examine and appraise the legal pluriverse surrounding these missions, and why a coherent legal framework which takes their factual complexities into account is necessary.119

To be sure, that is neither an easy nor obvious task. While practical challenges regarding multinational operations certainly haunt many military commanders and political decision-makers, it seems fair to say that sifting through the legal pluriverse in the attempt to provide systematic coherence is still in its infancy. It starts with identifying the legal situations a multinational military operation engages in: the determination whether it constitutes an international or a non-international armed conflict, or even an armed conflict in the first place,120 has wide-ranging implications for the rules applicable to the mission, stemming from international humanitarian law, international human rights law, or domestic law.121 Yet even this often less than straightforward assessment only solves part of the calculus. To some extent depending on the mandate, multilateral agreements such as the International Covenant on Civil and Political Rights or specifications (p.20) comprised in a UN Security Council resolution shape the mission’s outlines and influence the applicable legal framework.

But even then, it will still likely be the case that the different troop-contributing states and other actors involved are subject to widely different international obligations. While some legal regimes such as the Geneva Conventions or the UN Charter will apply to all,122 the individual states may commit to diverging status-of-forces agreements with the host state; they may not be party to the same international treaties that are applicable to the situation ratione materiae, such as the Protocols to the Geneva Conventions; they likely have varying rules of engagement, and their domestic laws or court decisions may impose irreconcilable national caveats on the respective missions. For example, during the KFOR operation in Kosovo, German forces could not be deployed to counter ongoing riots as they were legally prevented from using tear gas.123 This imperfect list shows the crucial importance of identifying and clarifying the applicable legal framework for all involved stakeholders, if possible, prior to the operation’s beginning—not least because the failure to meet the given legal standards may have a serious negative impact on the legitimacy and the prospects of success. If certain issues cannot be resolved beforehand, some states might be inclined to back out before committing forces to a legally fraught undertaking.124

At the same time, a number of legal questions will probably not arise before the troops of the multinational mission start operating on the ground. In such a case, there will be the need to find and establish specific solutions ad hoc under time pressure. Moreover, in the case that the dispatched troops have violated international law, the contentious question of attribution and (state) responsibility becomes pertinent. Depending on the mission’s operational and institutional design, numerous legal issues remain to be solved regarding this particular subject matter.125

To take stock of this legal pluriverse and to help make sense of it in order to gradually move towards a more coherent regime is the subject of the present book. The following section briefly outlines its five main parts and the legal problems that are dealt with by the contributing authors in their individual chapters.

4. The Structure of this Book

The book is divided into five main parts. Part I deals with the geographical and temporal scope of the laws of armed conflict, before the examination turns towards (p.21) different perspectives on the relationship between international humanitarian law and human rights law (Part II). The contributions in this section are followed by an analysis of the specific interaction of the laws of armed conflict and human rights law in a core area of the laws of armed conflict, namely the conduct of hostilities, with regard to detention, law enforcement, and precautions in attack in particular (Part III). Part IV tackles the role of public international law in relation to military operations, before Part V concludes the book with an investigation of the diversity of actors and its impact on the legal pluriverse surrounding multinational military operations.

4.1 Part I: The application and interoperability of the laws of armed conflict to multinational military operations

The application of the law of armed conflict to multinational military operations basically determines the legal framework on the basis of which the operation proceeds. Part I commences by analysing the legal implications of the application of international humanitarian law to multinational military operations.

Katja Schöberl considers the still contentious issue of the geographical scope of international humanitarian law in non-international armed conflicts, with particular attention to the challenges for multinational military operations. Christian Schaller explores the temporal scope of application of the laws of armed conflict in multinational military operations considering that determining the end of an armed conflict may not always be a straightforward exercise in situations of persistent instability. For that purpose, the chapter identifies and categorizes classes of rules with varying temporal dimensions. Michael Newton’s contribution closes the chapter with an in-depth analysis of the legal interoperability of the laws of armed conflict.

4.2 Part II: Laws of armed conflict and international human rights law in the context of multinational military operations: a matter of perspective?

Drawing on the findings of the first section, Part II is devoted to the long-standing discussion on the relationship between the laws of armed conflict and international human rights law. Typically, multinational military operations will operate at the very intersection of the two bodies of law. The section thus critically considers the increasingly prevalent albeit controversial presumption that given the fluidity and fragmentation of modern conflicts, a move towards further convergence of applicable standards is the appropriate way ahead.

(p.22) While Hans Boddens Hosang examines the relationship from an operational viewpoint, Kenneth Watkin offers a North American perspective on the debate and explains in detail why exclusionary approaches are, in general, favoured in the United States and Canada. In the subsequent chapter, Gentian Zyberi and Anna Andersson take the opposite view from a European standpoint. Arguing in favour of defragmentation, the authors carry out a comprehensive survey of the various instances of international humanitarian law (IHL) and international human rights law (IHRL) substantially influencing each other in contexts in which multinational military operations typically operate.

4.3 Part III: Laws of armed conflict and international human rights law in the context of multinational military operations: law enforcement, detention, hostilities, and precautions in attack as relevant cases in point

Part III further illustrates the proposition of substantive convergence and considers three crucial fields of significant operational importance in contemporary missions in which the fraught interplay between the laws of armed conflict and international human rights law becomes particularly relevant, namely law enforcement, detention, and the obligation to take precautions in attack.

Héctor Olásolo and his colleagues devote their case study to the legal difficulties that military missions face when fighting crime in times of armed conflict. When multinational military forces are, as is frequently the case, simultaneously engaged in genuine military operations as well as traditional law enforcement and policing tasks, they operate at the intersection of the laws of armed conflict and human rights law.

Detention in the context of multinational military operations is the focus of Jacques Hartmann’s contribution. Discussing a variety of recent court decisions regarding the issue—most prominently by the ECtHR—as well as relevant norm-finding efforts such as the Copenhagen process, and recent global state practice, the author analyses applicable legal bases, procedures, and constraints concerning detentions.

Marking one of the most discussed and critical cases regarding the relationship between the laws of armed conflict and human rights law, Andreas von Arnauld takes another look at the ECtHR’s decision in the case Hassan v UK. The author evaluates the decision with a focus on its prospective influence on the global debate regarding the relationship between the two bodies of law. Conversely, representing the exclusionary camp, Yaël Ronen offers an innovative line of argumentation against the application of human rights law to the extraterritorial conduct of hostilities by military operations.

(p.23) Geoffrey Corn then zooms in on the potential of precautionary measures for the effective protection of civilians from the perspective of IHL, with novel attention on the planning stage of military operations and the training of soldiers. As opposed to Corn, Tilmann Altwicker takes a progressive human rights approach to precautions. Analysing the ECtHR’s jurisprudence in this regard, the contribution compares precautions under IHL and IHRL, illustrating the mutual impact of both regimes.

4.4 Part IV: The role of pertinent subfields of public international law in relation to multinational military operations

The next part identifies the various other legal regimes that are part of the legal pluriverse surrounding multinational military operations, such as environmental law or the law of the sea, but also potentially mission-defining status-of-forces agreements.

While Pia Hesse examines UN Security Council resolutions as a legal framework for multinational military operations, Dieter Fleck devotes his contribution to an analysis of status-of-forces agreements, proposing policy guidelines on indispensable core elements of such agreements. Paulina Starski’s analysis focuses on the conditions under which wrongful conduct committed during multinational military operations can be attributed to international organizations or troop- and other contributing states. Furthermore, the prerequisites of multiple attribution and responsibility are examined.

The protection of the environment during multinational military operations is the focus of the subsequent chapter. Onita Das considers the ILC’s recent work regarding the issue but goes beyond these developments, exploring how multinational military operations are influenced more generally by international environmental law. The fourth part is concluded by Anna Petrig’s contribution on the law of the sea in relation to multinational military operations. Taking counter-piracy, counter-terrorism, and security interventions in the context of illegal fishing, drug- and weapons-trafficking as relevant examples, her chapter examines the rules applicable to maritime law enforcement operations.

4.5 Part V: Complex operational environments: diversity of actors and its impact on the legal pluriverse surrounding multinational military operations

Part V turns to the diversity of actors involved in or affected by multinational military operations. In particular, non-state armed groups may be subject to legal and factual asymmetries in relation to the multinational military operation. In light of (p.24) this, the section explores the extent of said asymmetry, and analyses its effects on the practice of the multinational mission.

In his contribution, Aurel Sari examines the additional legal dimensions brought into the legal pluriverse by the domestic laws of the territorial state on the one hand and the troop-contributing state on the other, which have the tendency to magnify conflicts between the different applicable legal regimes. Diverging domestic legal standards of troop-contributing states are frequently addressed by so-called national caveats, as Jochen Katze and Maral Kashgar show in their chapter. They explain the legal framework for such caveats, assess their significance, and analyse relevant recent jurisprudence.

In view of the fact that it is common practice to outsource various tasks to private security companies, Hin-Yan Liu analyses how this practice and the involvement of private actors affects the contracting state, the home state, and the territorial state in relation to the complexity of the legal framework of a multinational mission. Robert Frau exposes the various dimensions and implications of asymmetry in armed conflicts, particularly when multinational military operations are involved. Three aspects of asymmetry—legal, factual, and methodological—are identified. Finally, Andreas Müller highlights one especially material legal asymmetry, the question of human rights obligations of non-state armed groups. The contribution traces the evolution of international legal practice in this regard over the past decade.


(1) Quoted from K Harris, ‘Wartime Lies’ The New York Times (New York, 27 April 1997).

(2) V Bernard, ‘Editorial: Multinational Operations and the Law—Great Expectations, Great Responsibilities’ (2013) 95 International Review of the Red Cross 475, 475.

(3) M Zwanenburg, ‘International Humanitarian Law Interoperability in Multinational Operations’ (2013) 95 International Review of the Red Cross 681, 681.

(4) ibid.

(5) Bernard (n 2) 475.

(6) See for the European Union’s discussion regarding a common joint multinational force Council of the European Union, ‘Defence Cooperation: Council Establishes Permanent Structured Cooperation’ (PESCO) (Press Release, 11 December 2017) <https://www.consilium.europa.eu/en/press/press-releases/2017/12/11/defence-cooperation-pesco-25-member-states-participating/>, all URLs accessed 27 December 2018; see more recently the call by French President Emmanuel Macron and German Chancellor Merkel’s approval, ‘France’s Macron Pushes for “True European Army” ’ (BBC, 6 November 2018) <https://www.bbc.com/news/world-europe-46108633>; ‘Merkel Joins Macron in Calling for EU Army to Complement NATO’ (Politico, 13 November 2018) <https://www.politico.eu/article/angela-merkel-emmanuel-macron-eu-army-to-complement-nato/>.

(7) See United Nations, ‘Force Commanders Outline Challenges Facing United Nations Peacekeeping Efforts in Briefing to Security Council’ (Press Release, 23 May 2017) <https://www.un.org/press/en/2017/sc12834.doc.htm>.

(8) See eg the EU Mission in Kosovo EULEX, <https://www.eulex-kosovo.eu>.

(9) Eg as part of Operation Inherent Resolve in Iraq, <http://www.inherentresolve.mil>.

(10) Eg the Combined Task Force 150: Maritime Security, based in Bahrain, which was established to monitor, board, inspect, and stop suspect vessels as part of the ‘war on terrorism’.

(11) Eg the United Nations Transitional Administration in East Timor (UNTAET) from 1999 to 2002, <https://peacekeeping.un.org/mission/past/etimor/etimor.htm>.

(12) Eg in reaction to the 2010 monsoon floods in Pakistan, see JDP Moroney and others, ‘Lessons from Department of Defense Disaster Relief Efforts in the Asia-Pacific Region’ (RAND, 2013) <https://www.rand.org/content/dam/rand/pubs/research_reports/RR100/RR146/RAND_RR146.pdf>, 74 et seq.

(13) KJ McInnis, ‘Lessons in Coalition Warfare: Past, Present and Implications for the Future’ (2013) 1 International Politics Reviews 78, 81.

(14) ibid.

(15) ibid.

(16) K Hald Galster, ‘Introduction’ in Niels Bo Poulsen and others (eds), Coalition Warfare: An Anthology of Scholarly Presentations at the Conference on Coalition Warfare at the Royal (Danish Defence College, 2011) 13 et seq; RC Gross and I Henderson, ‘Multinational Operations’ in Geoffrey S Corn and others (eds), U.S. Military Operations: Law, Policy, and Practice (OUP 2015) 341, 341.

(17) Galster (n 16) 14.

(18) In some states such as Germany, constitutional provisions in some instances require military operations that are typically joint military operations under a mandate of an international organization that qualifies as a system of collective security, see Article 24(2) of the Basic Law for the Federal Republic of Germany.

(19) See N Higgins and K O’Reilly, ‘The Use of Force, Wars of National Liberation and the Right to Self-Determination in the South Ossetian Conflict’ (2009) 9 International Criminal Law Review 567.

(20) Bernard (n 2) 475.

(21) See UNSC Res 2381 (6 October 2017) UN Doc S/RES/2381.

(22) See European Council Decision on a European Union military mission to contribute to the training of the Malian Armed Forces (EUTM Mali) (17 January 2013) 2013/34/CFSP.

(23) See <https://peacekeeping.un.org/en/mission/minusca>; established by UNSC Res 2149 (10 April 2014) UN Doc S/RES/2149.

(24) UNSC Res 1973 (17 March 2011) UN Doc S/RES 1973.

(25) M Payandeh, ‘The United Nations, Military Intervention, and Regime Change in Libya’ (2012) 52 Virginia Journal of International Law 355.

(26) DR Rothwell and others, International Law. Cases and Materials with Australian Perspectives (3rd edn, CUP 2018) 716.

(27) K Bannelier and T Christakis, ‘Under the UN Security Council’s Watchful Eyes: Military Intervention by Invitation in the Malian Conflict’ (2013) 26 Leiden Journal of International Law 855.

(28) See JA Green, ‘The “Additional” Criteria for Collective Self-Defence: Request but not Declaration’ (2017) 4 Journal on the Use of Force and International Law 4; O Gross, ‘Unresolved Legal Questions Concerning Operation Inherent Resolve’ (2017) 52 Texas International Law Journal 1; K Bannelier and T Christakis, ‘Military Interventions Against ISIL in Iraq, Syria and Libya and the Legal Basis of Consent’ (2016) 29 Leiden Journal of International Law 743.

(29) UNSC Res 1769 (31 July 2007) UN Doc S/RES/1769.

(30) I Akwei, ‘ECOWAS Okays Military Intervention in Gambia, Joint Troops Stationed at Border’ (AfricaNews, 18 January 2017) <http://www.africanews.com/2017/01/18/ecowas-okays-military-intervention-in-gambia-joint-troop-stationed-at-border/>.

(31) See eg House of Commons, ‘The Legal Basis for the Invasion of Afghanistan’ (Standard Note, 26 February 2010) SN/IA/5340.

(32) MP Scharf, ‘How the War Against ISIS Changed International Law’ (2016) 48 Case Western Reserve Journal of International Law 1, 3.

(33) S Chesterman, ‘ “Leading from Behind”: The Responsibility to Protect, the Obama Doctrine, and Humanitarian Intervention after Libya’ (2011) 25 Ethics & International Affairs 279.

(34) Scharf (n 32) 48.

(35) A case in point is the mission in Mali, which started with a French-led military intervention in 2012 on the basis of a Security Council resolution and an invitation by the Malian government, before it gradually transformed into a United Nations peacekeeping mission (MINUSMA) and a European Union Training Mission (EUTM Mali) from 2013, see <https://minusma.unmissions.org/en/history>.

(36) P Starski, ‘Zurechnungsfragen bei multinationalen militärischen Einsätzen’ in S Kielmansegg, H Krieger, and S Sohm (eds), Multinationalität und Integration im militärischen Bereich—Eine rechtliche Perspektive (Nomos 2018) 163–208.

(40) Starski (n 36) 17.

(41) AMISOM, see <http://amisom-au.org/>.

(42) UNSC Res 1744 (21 February 2007) UN Doc S/RES/1744.

(44) UNSC Res 1386 (20 December 2001) UN Doc S/RES/1386.

(45) Bernard (n 2) 476.

(46) C Dale, ‘Operation Iraqi Freedom: Strategies, Approaches, Results, and Issues for Congress’, CRS Report for Congress, updated 28 March 2008, 32.

(47) W Assanvo and others, ‘Assessing the Multinational Joint Task Force against Boko Haram, West Africa Report’ (Institute for Security Studies, September 2016) <https://issafrica.s3.amazonaws.com/site/uploads/war19.pdf>.

(48) B Nußberger, ‘Military Strikes in Yemen in 2015: Invitation by Invitation and Self-Defence in the Course of Yemen’s “Model Transitional Process” ’ (2017) 4 Journal on the Use of Force in International Law 110; for an assessment of plans to institutionalize the cooperation among Arab states see J Noll and S Roll, ‘From Yemen War to Joint Army? Egyptian-Saudi Differences over Arab Military Cooperation’ (May 2015) 31 SWP Comments.

(49) Bannelier and Christakis (n 27); A Seyedfarshi, ‘French Interventionism in the Age of R2P: A Critical Examination of the Case of Mali’ (2015) 7 Creighton International and Comparative Law Journal 2.

(50) RL DiNardo, ‘Coalition and Alliance War’ (Oxford Bibliographies Online, 22 April 2013) <http://www.oxfordbibliographies.com/view/document/obo-9780199791279/obo-9780199791279-0108.xml>.

(51) Galster (n 16) 1.

(52) See for an attempt to exhaustively and systematically compile all relevant alliances since 1648 (not limited to, but with a heavy focus on the West) DM Gibler, ‘International Military Alliances 1648–2008’ (CQ Press 2009).

(53) Encyclopaedia Britannica, ‘Dutch War 1672–1678’ <https://www.britannica.com/event/Dutch-War>.

(54) DiNardo (n 50).

(55) GE Rothenberg and J Keegan, The Napoleonic Wars (Cassell 1999) 16.

(56) OR Holsti and others, Unity and Disintegration in International Alliances (Wiley 1973) 22.

(57) Galster (n 16) 11.

(58) JB Agnew, ‘The Great War That Almost Was: The Crimea 1853–1856’ (1973) 3 Parameters 46.

(59) J Black, Combined Operations. A Global History of Amphibious and Airborne Warfare (Rowman & Littlefield 2018) 97.

(60) R Foot and C Miller, ‘Canada and the South African War’ (The Canadian Encyclopedia, 2006) <https://www.thecanadianencyclopedia.ca/en/article/south-african-war>; RG Haycock, ‘The Alliance Proving Grounds: Canada in the Anglo-Boer War and the Great War’ in RS Rush and WW Epley (eds), Multinational Operations, Alliances, and International Military Cooperation. Past and Future (Center for Military History, US Army 2006) 39.

(61) DJ Silbey, The Boxer Rebellion and the Great Game in China (Hill and Wang 2012).

(62) SJ Cimbala and PK Forster, Multinational Military Intervention. NATO Policy, Strategy and Burden Sharing (Ashgate Publishing 2010) 193 et seq.

(63) JB Agnew, ‘Coalition Warfare: A Successful Experiment in Combined Command, 1914–1918’ (1971) 1 Parameters 50, 56.

(64) ibid 63 et seq.

(65) M Matloff, Strategic Planning for Coalition Warfare, 1943–1944 (Office of the Chief of Military History Department of the Army 1959) 5.

(66) G Feifer, The Great Gamble: The Soviet War in Afghanistan (Harper Perennial 2010).

(67) G Merom, How Democracies Lose Small Wars. State, Society, and the Failures of France in Algeria, Israel in Lebanon, and the United States in Vietnam (CUP 2003) 83 et seq.

(68) J Colman, ‘The Challenges of Coalition-Building: The Vietnam Experience, 1964–1969’ (RUSI, 15 March 2010) <https://rusi.org/commentary/challenges-coalition-building-vietnam-experience-1964-1969>.

(69) Encyclopaedia Britannica, ‘Arab-Israeli Wars’ <https://www.britannica.com/event/Arab-Israeli-wars>.

(70) A Shlaim, ‘Israel and the Arab Coalition in 1948’ in E Rogan and A Shlaim (eds), The War for Palestine: Rewriting the History of 1948 (2nd edn, CUP 2007) 79.

(71) See in detail A Kober, Coalition Defection: The Dissolution of Arab Anti-Israeli Coalitions in War and Peace (Praeger 2002).

(72) H Mashhud Choudhry, Coalition Warfare—Can the Gulf War-91 Be the Model for Future? (US Army War College 1992).

(73) UNSC Res 678 (29 November 1990) UN Doc SC/RES/678.

(74) Cimbala and Forster (n 62) 4.

(75) ibid 5.

(76) The Hague Institute for Global Justice, ‘International Decision-Making in the Age of Genocide: Srebrenica 1993–1995’ (Rapporteur Report, The Hague 2015) 2 et seq.

(77) S Daley, ‘After the Attacks: The Alliance; For First Time, NATO Invokes Joint Defense Pact with U.S.’ The New York Times (New York, 13 September 2001) A00017.

(78) AJ Rubin, ‘NATO Chief Promises to Stand by Afghanistan’ The New York Times (New York, 22 December 2009) A14; Cimbala and Forster (n 62) 149 et seq.

(79) S Schifferes, ‘US Names “Coalition of the Willing” ’ (BBC News, 18 March 2003) <http://news.bbc.co.uk/2/hi/americas/2862343.stm>.

(80) See only R Hatto, ‘From Peacekeeping to Peacebuilding: The Evolution of the Role of the United Nations in Peace Operations’ (2013) 95 International Review of the Red Cross 495; JT O’Neill and N Rees, United Nations Peacekeeping in the Post-Cold War Era (Routledge Chapman & Hall 2005); A Adebajo, UN Peacekeeping in Africa: From the Suez Crisis to the Sudan Conflicts (Lynne Rienner Publishers 2011); for an examination of the applicable law see T Gill and others (eds), Leuven Manual on the International Law Applicable to Peace Operations (CUP 2017).

(81) See M Goulding, ‘The Evolution of United Nations Peacekeeping’ (1993) 69 International Affairs 451, 452.

(82) Bernard (n 2) 478.

(83) Gill (n 80) 6 et seq.

(84) United Nations Peacekeeping, ‘Peacekeeping Operations Fact Sheet’ (30 April 2018) <https://peacekeeping.un.org/sites/default/files/pk_factsheet_04_18_eng_0.pdf>.

(85) Bernard (n 2) 477.

(86) Gill (n 80) 8.

(87) IA Badmus, ‘The African Mission in Burundi (AMIB): A Study of the African Union’s Peacekeeping Success and “Triangular Area of Tension in African Peacekeeping” ’ (2017) 73 India Quarterly: A Journal of International Affairs 1.

(88) Gill (n 80) 20.

(89) Human Rights Watch, ‘Sudan: Imperatives for Immediate Change. The African Union Mission in Sudan’ (19 January 2006) <https://www.hrw.org/report/2006/01/19/sudan-imperatives-immediate-change/african-union-mission-sudan>.

(90) E Svensson, ‘The African Union’s Operations in the Comoros. MAES and Operation Democracy, Defence Analysis’ (Swedish Defence Research Agency, Stockholm 2008) <http://www.operationspaix.net/DATA/DOCUMENT/5040~v~The_African_Union__8217s_Operations_in_the_Comoros.pdf>.

(91) M Caparini, ‘The Mali Crisis and Responses by Regional Actors, NUPI Working Paper 849’ (Norwegian Institute of International Affairs, Oslo 2015) <https://brage.bibsys.no/xmlui/bitstream/id/366213/NUPI_WP_849+Marina+Caparini.pdf>.

(94) ibid 23.

(96) Gill (n 80) 24.

(97) Galster (n 16) Preface; see already the National Security Strategy of the U.S. 1994, available at <http://nssarchive.us/NSSR/1994.pdf>, 6 et seq.

(98) Cimbala and Forster (n 62) 9.

(99) R Geiß and A Petrig, Piracy and Armed Robbery at Sea: The Legal Framework for Counter-Piracy Operations in Somalia and the Gulf of Aden (OUP 2011); M Sterio, ‘Fighting Piracy in Somalia (and Elsewhere): Why More is Needed’ (2009) 33 Fordham International Law Journal 372; Eric A Heinze, ‘A “Global War on Piracy?” International Law and the Use of Force against Sea Pirates’ in MJ Struett and others (eds), Maritime Piracy and the Construction of Global Governance (Routledge 2013) 47.

(100) Bannelier and Christakis (n 28); MP Scharf, ‘How the War against ISIS Changed International Law’ (2016) 48 Case Western Reserve Journal of International Law 16.

(101) Cimbala and Forster (n 62) 207.

(102) ibid 14.

(103) ibid 28.

(104) Gill (n 80) 17.

(105) See Peacekeeping Operations Fact Sheet (n 84).

(107) See generally Gill (n 80).

(108) S Hill and D Lemétayer, ‘Legal Issues of Multinational Military Operations: An Alliance Perspective’ (2016) 55 Military Law and the Law of War Review 13, 17.

(109) Starski (n 36); P Palchetti, ‘The Allocation of Responsibility for Internationally Wrongful Acts Committed in the Course of Multinational Operations’ (2013) 95 International Review of the Red Cross 727.

(110) See for an overview eg G Nolte (ed), European Military Law Systems (De Gruyter 2003).

(111) N Leonhard, ‘Multinational Co-operation within the MNTF SE in Mostar—General Conclusions’ in N Leonhard and others (eds), Military Co-operation in Multinational Missions: The Case of EUFOR in Bosnia and Herzegovina (SOWI 2008) 241, 244 et seq.

(112) Galster (n 16) 10.

(113) ibid 13 et seq.

(114) M Smolarek, ‘Challenges for Leading Multinational and Multicultural Military Units’ (2016) 2 Journal on Baltic Security 183, 191.

(115) I Goldbach and F Rapan, ‘The Effects of Cultural Interactions in Multinational Military Missions’ (International Conference RCIC’17, Bucharest 2018) 420, 423.

(116) McInnis (n 13) 83.

(117) Galster (n 16) 8; A van Dijk, ‘Tough Talk: Clear and Cluttered Communication during Peace Operations’ in J Soeters and P Manigart (eds), Military Cooperation in Multinational Peace Operations. Managing Cultural Diversity and Crisis Response (Routledge 2008) 70.

(118) McInnis (n 13) 88.

(119) Bernard (n 2) 479.

(120) E David and O Engdahl, ‘How Does the Involvement of a Multinational Peacekeeping Force Affect the Classification of a Situation?’ (2013) 95 International Review of the Red Cross 659.

(121) Bernard (n 2) 480.

(122) Gross and Henderson (n 16) 342.

(123) See Chapter 19 by Katze and Kashgar in this book.

(124) Gross and Henderson (n 16) 343.

(125) Starski (n 36) 3.