Understanding battlefield coalitions

ABSTRACT

Battlefield coalitions are distinct warfighting collectives. They are the groups of forces created by states that are formal allies, states that have no written agreement to cooperate militarily, non-state actors, or some combination thereof to engage in combat at the operational and tactical levels of war. They are also increasingly common belligerents in war, but there is little scholarship on their creation, composition, operation, and achievements. This special issue begins the necessary work of improving our understanding of battlefield coalitions, providing new insight into their nature and capabilities, as well as the military and political consequences of their combat operations.

KEYWORDS:

• War
• battle
• battlefield coalitions
• military effectiveness
• non-state actors

War is an inherently collective activity. At minimum, two belligerents bring together large numbers of soldiers and officers to fight in coordination against a similar collection of individuals as the sides contest some political objective. Often, there is an additional layer of collective effort as, on one or both sides of a battle, multiple belligerents band together to combat their common foe. These latter types of collectives, featuring the forces of multiple belligerents fighting side-by-side in combat, recur throughout history. Alexander confronted, and defeated, many different battlefield coalitions on his march through the Balkans, Asia Minor, Persia, and India between 336 and 323 BCE. Similarly, various Gallic tribes often combined in their attempts to try to stem Julius Caesar’s drive into their territory between 58 and 50 BCE. During the First Crusade, waged 1096–1099, loose confederations of forces totalling approximately 100,000 men and headed by various European nobles marched on the Holy Land and eventually took Jerusalem. During the Imjin War, fought 1592–1598, a coalition of Chinese and Korean forces repulsed repeated Japanese attempts to invade and conquer territory on the Asian mainland. Between 1600 and 1783, myriad Native American tribes of the Iroquois nations formed coalitions to fight combat actions with and against European explorers and settlers. Both World Wars featured coalitions of belligerent states on both sides of many battlefields. More recently, the United States brought together coalitions of forces to fight combat actions in the Balkans, Iraq, and Afghanistan, often against other coalitions comprised of both state and non-state actors.

Despite their common and consistent presence in military and political affairs, battlefield coalitions – amalgams of officers, troops, and materiel brought together by multiple distinct political communities for the purpose of jointly waging combat in the same operational battlespace – have been largely overlooked in the study of collective warfighting. Instead, scholars have generally trained their focus on the creation, organization, operation, and termination of alliances and wartime coalitions. By the terms of one prominent formulation, alliances are ‘written agreements, signed by official representatives of at least two independent states, that include promises to aid a partner in the event of military conflict, to remain neutral in the event of conflict, to refrain from military conflict with one another, or to consult/cooperate in the event of international crises that create a potential for military conflict’.¹ Wartime coalitions, per common usage, are ‘group[s] of states that coordinate military activity during a war, regardless of the nature of the pre-war relationship’.²

This focus in existing scholarship limits its applicability to the study of battlefield coalitions because such groups are distinct from both alliances and wartime coalitions. As noted, alliances and wartime coalitions are political and strategic arrangements between partners, created to align war aims and military objectives in war against a common foe. Battlefield coalitions are the subgroups those partners create to engage the adversary at the operational and tactical levels of warfighting. Significantly, both alliance and wartime coalition partners may choose to create battlefield coalitions – they may do so in all battles waged during their common war or in some battles but not others. They may also choose not to create battlefield coalitions during their combined fight against an adversary, preferring instead to deploy their units individually. Battlefield coalitions are further distinguished from alliances and wartime coalitions in that they are not necessarily comprised only of forces raised by states: they may include, or even be wholly comprised of, troops deployed by non-state actors. Battlefield coalitions thus represent a separate and crucial link in the causal chain connecting the application of military means with political ends. Understanding more about them – their creation, composition, organization, performance, and associated military and political consequences – will illuminate important relationships between military force, political objectives, and patterns of outcomes in the international arena.

Some existing scholarship does shed light directly on battlefield coalitions, though it has overwhelming focused on combined forces drawn from groups of states that are part of formal alliances like the North Atlantic Treaty Organization (NATO),³ led by the United States,⁴ or fighting during the World Wars and Korean War.⁵ Yet, while these studies provide important insights, battlefield coalitions more often than not are ad hoc, drawing together forces from states that do not have prior agreements to fight alongside one another in war; do not involve the United States; and fight in conflicts other than the World Wars and Korean War.⁶ It is unclear whether and to what degree existing understandings of battlefield coalitions can be generalised to the broader universe of such collectives.

An additional consequence of the focus in existing scholarship on alliances and wartime coalitions is the under-examination of non-state actors as part of battlefield collectives. There is a small literature on battlefield coalitions that include forces fielded by non-state actors, but it tends to focus on the formation and disintegration of such groups rather than how they operate in combat.⁷ A substantial minority of battlefield coalitions fighting in the twentieth century featured a wide array of non-state actors, ranging from hyperlocal partisans like the Boxers in China to transnational millenarian terrorists like al Qaeda, fighting both alongside states and in combination with other non-state actors; understanding how such groups function in combat requires further investigation.⁸

The universe of battlefield coalitions is far more vast, and the questions to be answered about them are much more numerous, than is reflected in existing scholarship. Especially because such groupings are increasingly common in conflicts around the world, a renewed, more focused effort at understanding them and their role in the international arena is needed.⁹

The articles in this issue

This special issue begins the necessary work of reinvigorating scholarship on battlefield coalitions, providing new insight into such groups’ creation, composition, organization, and performance as well as the military and political consequences of their operations in combat. The collected articles do so by drawing on ideas, theories, and findings from various literatures in international relations, strategic studies, and military operations – including, but not limited to, the literatures on formal alliances, organizational theory, bargaining, and military adaption – to develop new frameworks for analysis. They illustrate the value and potential of a renewed scholarly focus on battlefield coalitions with rich empirical details, generated from newly collected data, robust case studies, close readings of primary sources, and participant interviews.

A portrait of battlefield coalitions

To begin to understand battlefield coalitions, it is necessary to first know something about them as a phenomenon in the international arena. Accordingly, the issue begins with what is to date the only systematic overview of the presence, composition, and performance of such collectives in interstate wars. Using newly collected data, Rosella Cappella Zielinski and Ryan Grauer's ‘A Century of Coalitions in Battle: Incidence, Composition, and Performance, 1900–2003ʹ reports that battlefield coalitions are common, and powerful, actors in interstate wars. Crucially, there are important variations across battlefield coalitions in terms of their performance and such groups are becoming more common as well as more likely to include non-state actors over time.

With this clearer understanding of what the universe of battlefield coalitions looks like, the other articles in this special issue investigate particular characteristics of such groups’ composition, operation, and military and political achievements.

Expanding the roster of battlefield coalition members

The first set of articles takes up the issue of who fights in a battlefield coalition, and how, with a particular emphasis on the peculiar status of non-state actors. In ‘Command and Military Effectiveness in Rebel and Hybrid Battlefield Coalitions,’ Dan Reiter theorizes a broader understanding of battlefield coalitions and considers the drivers of member behaviour in groups including only forces drawn from states, groups including only forces drawn from non-state actors, and groups including forces drawn from both types of belligerents. In doing so, Reiter underscores the differences in variously comprised battlefield coalitions, arguing that state and non-state actor incentives to invest in contextually appropriate command structures – the authority relations that condition groups’ chances of success in combat – diverge along predictable dimensions.

Barbara Elias, in ‘Why Rebels Rely on Terrorists: The Persistence of the Taliban-al-Qaeda Battlefield Coalition in Afghanistan,’ investigates the choices made by members of a particular form of battlefield coalition comprised solely of non-state actors. In particular, Elias moves beyond the state/non-state distinction in battlefield coalitions and investigates the conditions under which different types of non-state actors – rebel groups and terrorist organizations – persist in forming battlefield coalitions over time, pointing toward both political and military factors that shape their decisions.

Battlefield coalition operations

The next two articles collectively investigate how battlefield coalitions coordinate their plans and combat activities to ensure that the partners do not work at cross purposes when bullets begin to fly and maximize their chances of achieving their combined objectives. Stéfanie von Hlatky and Thomas Juneau’s ‘When the Coalition Determines the Mission: NATO’s Detour in Libya’ and Sara Moller's ‘Learning from Losing: How Defeat Shapes Coalition Dynamics in Wartime’ each note that the challenge of coordination is a significant barrier to effective battlefield coalition operations – mandates given to such groups by their home governments are often unclear and complicated by concerns about autonomy under fire – and is only overcome through careful, considered effort.

Von Hlatky and Juneau argue that, in the face of unclear mandates, a variety of domestic and international political factors drive battlefield coalitions’ definition of their combined mission. Complex considerations of partners’ relative power, freedom of action, and role within the group all shape intra-coalitional negotiations and, ultimately, the content of the mission they pursue together in combat. Moller then takes up the question of how battlefield coalitions execute their missions and argues that battlefield performance is likely to drive organizational change. In particular, when combined losses begin to mount, battlefield coalitions are likely to sacrifice their autonomy in combat for additional coordination capabilities and, ideally, improved chances for victory.

What battlefield coalitions achieve

The final article in this special issue places battlefield coalitions in their larger context and examines how their composition and achievements can affect broader war and political outcomes. In ‘Speaking with One Voice: Coalitions and Wartime Diplomacy,' Eric Min considers the conditions under which battlefield coalition partners are likely to defect from the collective effort to combat a common foe and individually initiate negotiations that could end their own participation in the war, or perhaps the conflict more generally. The relative balance of power within a battlefield coalition and the group’s performance interact, with both victories and defeats motivating defection under different circumstances.

Battlefield coalitions in international relations

The articles in this special issue thus offer important new insights into frequency, composition, performance, and political achievements of battlefield coalitions. Their arguments and findings have important implications for both scholars and policymakers. For the former, they represent new views into the causal chain connecting the use of force to patterns of outcomes in the international arena as well as the nature and challenges of collective action in perhaps the most inhospitable environment imaginable. For the latter, they point toward the need to think more carefully about how domestic and international factors may shape the potential for collaboration in combat as well as the need to take seriously the challenges and best practices of working well with non-state actors.

Still, these articles represent only the beginning of the work that remains to be done. Even a short list of questions about battlefield coalitions that require further investigation is daunting. For example, sovereignty concerns loom large in creating and organizing battlefield coalitions – are certain types of states more or less likely to relinquish some sovereign rights than others? Does the identity of coalition partners matter for such decisions? Do the same factors driving states’ actions with regard to their sovereignty drive non-state actors and their concerns about autonomy in the context of battlefield coalition operations? Once battlefield coalitions are created and organized, how can common barriers to collective action like shirking and free-riding be minimized and exploitation of the partners’ comparative advantages be maximized? How well do such barriers and advantages need to be managed to facilitate effective combined performance in combat? What role do time and experience play in conditioning how battlefield coalition partners work together? Thinking more broadly, are actors that come together to cooperate as battlefield coalition partners likely to build on that experience and cooperate in other realms? Or perhaps do such cooperative spill-over effects depend on performance?

The research agenda on battlefield coalitions and their impact in international relations is thus quite robust; increasing our collective understanding of these groups and their impact on broader military and political dynamics will require the efforts of many scholars. We regard the articles collected in this special issue as the start of a vigorous conversation, and hope that they inspire others to take up the many questions that remain to be answered.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Notes on contributors

Rosella Cappella Zielinski

Rosella Cappella Zielinski is an Associate Professor of Political Science at Boston University, a visiting fellow at the Clements Center for National Security at the University of Texas at Austin, and non-resident fellow at the Brute Krulak Center for Innovation and Creativity at Marine Corps University. She is the author of How States Pay for Wars (Ithaca, NY: Cornell University Press, 2016) winner of the 2017 American Political Science Association Robert L. Jervis and Paul W. Schroeder Best Book Award in International History and Politics. Her other works can be found in the Journal of Peace Research, Conflict Management and Peace Science, Security Studies, European Journal of International Relations, Journal of Global Security Studies, as well as Foreign Affairs, Texas National Security Review, and War on the Rocks. Her research interests include the areas of political economy of security and collective warfare.

Ryan Grauer

Ryan Grauer is an Associate Professor of International Affairs in the Graduate School of Public and International Affairs at the University of Pittsburgh. His research investigates the creation and use of military power in the international arena. He is the author of Commanding Military Power (Cambridge University Press, 2016). His other work can be found in World Politics, the European Journal of International Relations, Security Studies, and the Journal of Global Security Studies.

Notes

¹ Brett Ashely Leeds et al., ‘Alliance Treaty Obligations and Provisions, 1815–1944’, International Interactions 28/3 (2002): 238. For recent reviews of the copious literature on alliances, see Patricia A. Weitsman, ‘Alliances and War’, in Oxford Research Encyclopedia of International Studies (Oxford: Oxford University Press, 2017); Sten Rynning and Olivier Schmitt, ‘Alliances’, in The Oxford Handbook of International Security, ed. Alexandra Gheciu and William C. Wohlforth (Oxford: Oxford University Press, 2018).

² Daniel S. Morey, ‘Military Coalitions and the Outcome of Interstate Wars’, Foreign Policy Analysis 12/4 (October 2016): 535. On wartime coalitions, see, for example, Patricia Weitsman, ‘Wartime Alliances versus Coalition Warfare: How Institutional Structure Matters in the Multilateral Prosecution of Wars’, Strategic Studies Quarterly 4/2 (Summer 2010): 113–36; Scott Wolford, The Politics of Military Coalitions (New York: Cambridge University Press, 2015); Patrick A. Mello and Stephen M. Saideman, ‘The Politics of Multinational Military Operations’, Contemporary Security Policy 40/1 (January 2019): 30–37; Marina E. Henke, Constructing Allied Cooperation: Diplomacy, Payments, and Power in Multilateral Military Coalitions (Ithaca, NY: Cornell University Press, 2019).

³ See, for example, Ivo H. Daalder and Michael E. O’Hanlon, Winning Ugly: NATO’s War to Save Kosovo (Washington, DC: Brookings Institution Press, 2004); Patricia Weitsman, Waging War: Alliances, Coalitions, and Institutions of Interstate Violence (Stanford, CA: Stanford University Press, 2013); David P. Auerswald and Stephen M. Saideman, NATO in Afghanistan: Fighting Together, Fighting Alone (Princeton: Princeton University Press, 2014); Olivier Schmitt, ‘International Organization at War: NATO Practices in the Afghan Campaign’, Cooperation and Conflict 52/4 (December 2017): 502–18.

⁴ See, for example, Weitsman, ‘Wartime Alliances versus Coalition Warfare’; Sarah E. Kreps, Coalitions of Convenience: United States Military Interventions after the Cold War (New York: Oxford University Press, 2011); Weitsman, Waging War; Olivier Schmitt, Allies That Count: Junior Partners in Coalition Warfare (Washington, DC: Georgetown University Press, 2018).

⁵ See, for example, Patricia Weitsman, Dangerous Alliances: Proponents of Peace, Weapons of War (Stanford, CA: Stanford University Press, 2003); Kelly Ann Grieco, ‘War by Coalition: The Effects of Coalition Military Institutionalization on Coalition Battlefield Effectiveness’ (PhD thesis, Cambridge, MA, Massachusetts Institute of Technology, 2016); Sara Bjerg Moller, ‘Fighting Friends: Institutional Cooperation and Military Effectiveness in Multinational War’ (PhD thesis, New York, Columbia University, 2016); Alex Weisiger, ‘Exiting the Coalition: When Do States Abandon Coalition Partners during War?’ International Studies Quarterly 60/4 (December 2016): 753–65; Rosella Cappella Zielinski and Ryan Grauer, ‘Organizing for Performance: Coalition Effectiveness on the Battlefield’, European Journal of International Relations 26/4 (December 2020): 953–78; Rosella Cappella Zielinski, Ryan Grauer, and Alastair Smith, ‘Regime Type, War Aims, and Coalition Member Effort in Combat’ (Manuscript, Boston, MA; Pittsburgh, PA; New York, 2021).

⁶ Rosella Cappella Zielinski and Ryan Grauer, ‘A Century of Coalitions: Incidence, Composition, and Performance, 1900-2003,’ this issue.

⁷ See, for example, Fotini Christia, Alliance Formation in Civil Wars (New York: Cambridge University Press, 2012); Seden Akcinaroglu, ‘Rebel Interdependencies and Civil War Outcomes’, Journal of Conflict Resolution 56/5 (October 2012): 879–903; Michael Woldemariam, ‘Battlefield Outcomes and Rebel Cohesion: Lessons From the Eritrean Independence War’, Terrorism and Political Violence 28/1 (January 2016): 135–56; Peter Rudloff and Michael G Findley, ‘The Downstream Effects of Combatant Fragmentation on Civil War Recurrence’, Journal of Peace Research 53/1 (January 2016): 19–32; Emily Kalah Gade, Mohammed M Hafez, and Michael Gabbay, ‘Fratricide in Rebel Movements: A Network Analysis of Syrian Militant Infighting’, Journal of Peace Research 56/3 (May 2019): 321–35.

⁸ Cappella Zielinski and Grauer, ‘A Century of Coalitions,’ this issue.

⁹ Ibid.