PhD Clara Egger
email: clara.egger@umrpacte.fr

THE EXPLICIT AUTHORIZATION OF THE AUTHOR. COMMENTS ARE WELCOME

Being the best at winning the peace. NATO and EU rival development of a comprehensive approach to crisis management

Clara Egger

To cite this version:

Clara Egger. Being the best at winning the peace. NATO and EU rival development of a comprehensive approach to crisis management. 2013.

"We are trying to build a global crisis-management organization including military and civil assets. Nothing like this exists in the world" ( EU senior official quoted in Bretherton & Vogler, 1999, p. 45) "For us, NATO is not the appropriate actor to implement a comprehensive approach? It is not an actor to do so, I speak about comparative advantages. Of course NATO is a collective security actor that should not be involved in reconstruction or development operations. Firstly it does not have the same level of financial resources than the EU. And secondly, because, sorry to insist, it is not its business" (Interview, French Ministry of Defence, 2012).

As the above mentioned quotations underline, the current development of the European Union (EU) and the North Atlantic Treaty Organization (NATO) comprehensive approach is characterized by an open rivalry between both organizations. Both actors strive to be recognized as the favorite regional peacekeeper of the United Nations (UN). The EU points at its "uniqueness" as an actor gathering civilian and military capabilities whereas NATO emphasizes its highly efficient military might.

The dynamics of EU/NATO relationship and the current competition between both organizations are closely linked to the evolution of the European security architecture. The end of the Cold War and the development of the European Security and Defence Policy (ESDP) have deeply affected the relations between EU and NATO.

During the Cold War, the division of tasks between actors was rather simple and clear. The United Nations delegated to regional organizations the management of crises occurring in their geographic area of competence. Europe was divided into two blocks, each having its own organization with a clear mandate in terms of security issues. The competences of NATO were rather clear since it was the only Western alliance. With the failure of initial attempts to develop a common defence policy, the EU mainly focuses on promoting economic integration between its Member States and on institution-building.

Two key changes will affect this division of labor between NATO and the EU. First of all, the end of the Cold War raised questions about the capacity of an alliance to survive the disappearance of the hegemonic threat it was built against [START_REF] Irondelle | L'OTAN est-elle encore l'OTAN1?[END_REF].At the same time, the EU embarked on a process of developing a "harder" identity on the external scene, based on the development of defense and military capacities. These developments led to a greater proximity between NATO and the EU and gave birth to one of the most densely institutionalized inter-organizational partnership [START_REF] Koops | NATO's Influence on the Evolution of the European Union as a Security Actor[END_REF]. The EU-NATO Declaration on the ESDP and the Berlin Plus agreement provided a clear basis for partnership. Co-operation became operationalized in two cases: the operation Concordia in Macedonia, and the operation Althea in Bosnia-Herzegovina.

But the NATO-EU honey moon didn't last long. Few years after the first implementation of the Berlin Plus agreement, tension arose between the partners. The war in Iraq triggered strong divergences of view between pro-Atlanticists and pro-Europeanists. The EU started a

NATO/EU relationship in the litterature

The starting point of the literature dealing with the relations between NATO and the EU is the statement that, with the end of Cold War and the disappearance of the Soviet threat, an alliance like NATO has lost its relevance. Debates about the future of NATO have always had the relation with the EU in the background. The necessity to analyze how the relations between a new NATO and a politically stronger EU may organize became even more relevant with the expansion of both organizations' membership and with the development of the EU common defense and security policy.

Other studies adopt either an EU-centric perspective, or a transatlantic perspective, evoking the EU/NATO relationship en passant either dealing with the increasing role of the EU in the European Security architecture (and implicitly addressing its impacts on NATO) or with the future of the transatlantic relations in the context of the "revolution" in European Defense and Security Policy [START_REF] Cornish | European Security: The End of Architecture and the New NATO[END_REF].

Very few studies analyze the EU/NATO relationship as such. We will therefore report here some of the key work adopting this perspective. These studies share a number of similarities. First of all they tend to exclusively focus on the role of key Member States (the US, the UK, France and Turkey) in enabling or, in the contrary, hindering the cooperation between NATO and the EU. They tend to leave aside factors situated at the organizational level. Another common feature of these works is their normative character. Most of these works are published by think-tanks aiming either to save NATO, or to improve EU/NATO relationships [START_REF] Cornish | Beyond EU/NATO dichotomy1: the beginnings of a European strategic culture[END_REF][START_REF] Hunter | The European Security and Defense Policy. NATO's Companion or Competitor1? Rand Europe[END_REF][START_REF] Moens | Thinking Outside the Box. NATO-ESDP Cooperation at 23[END_REF].

In his contribution to the book he edited, Moens analyzes how the development of the EU capacities was perceived by the US. He focuses on two key obstacles for cooperation : the position of Turkey (and more largely of other NATO non-EU members), and the lack of a clear understanding on how separate or joint NATO and EU decision-making structures, military planning and operational preparedness mechanisms may be ; both problems being perceived as interrelated (Moens, 2003, p. 72). Another obstacle for cooperation lies in the "too protective" character of the Berlin Plus Agreement, leading to institutional defensiveness (Moens, 2003, p. 76). However the author does not develop this argument, with an analysis fo the content of Berlin Plus. Other factors are mentioned such as the impact of overlapping mandates, but without a structured analysis of such organizational factors, the research focusing mainly on a state-centric level (Moens, 2003, p. 77).

The work of Hunter adopts a more descriptive stance and analyzes the reaction of the US and of NATO officials to the development of the EU capabilities. The author does not focus on the dynamics of the NATO-EU relationship as such [START_REF] Hunter | The European Security and Defense Policy. NATO's Companion or Competitor1? Rand Europe[END_REF]. It is only in the chapter 11, that the author exposes some explanatory factors of the relationship such as a) the role of a common military and economic culture ; b) the role of UK and France in keeping NATO and the EU at distance; c) the issue of a potential European caucus in NATO, d) the role of the defense production and trade and e) the position of both organizations towards its role in crisis-management activities (Hunter, 2002, pp. 72-83). Each factor is not really analyzed even if the fifth one is key to understand the rivalry between NATO and the EU. Indeed, the ESDP is conceived as a tool of a broader EU capacity in external affairs. The EU can therefore mobilize a full spectrum of activities such as conflict prevention, diplomacy, humanitarian and development work, reconstruction programs. On the contrary NATO stands as a "stand-alone" organization only having military capacities (Hunter, 2002, p. 83). Hunter rarely uses organizational factors to explain the nature of NATO/EU relationship with one notable exception when he focuses on the specific mandate of the NATO Secretary General and on the role of the North Atlantic Committee both lacking a unified political view on what should be done to solve a crisis, once the military intervention is over (Hunter, 2002, p. 84). At the end of his book, Hunter develops practical recommendations directed towards European policy-makers. Such recommendations focus on the defense of NATO's primacy without any clear justification of this stance. The author especially advices the EU to exercise "rhetoric restraint" and to respect NATO primacy (Hunter, 2002, pp. 149-156).

Cornish and Edwards focus on the need to create a proper European strategic culture , likely to include diverging positions without forecasting the future and being a threat to NATO [START_REF] Cornish | Beyond EU/NATO dichotomy1: the beginnings of a European strategic culture[END_REF]. Here again the focus is not really on the relationship between EU and NATO but rather on the impact that the development of EU capacities may have on NATO. Some key institutional factors are however evoked but never developed such as the inter-institutional rivalry between the Commission and the Council (Cornish & Edwards, 2001, pp. 594-595), the role of institutional learning and socializing forces especially with regards to the military community (Cornish & Edwards, 2001, p. 595) and the difference in terms of organizational culture between NATO and the EU, the latter being characterized by a diplomatic culture whereas the former having a defence culture (Cornish & Edwards, 2001, p. 596).

Howorth and Paroissien propose to limit the UE/NATO relationship between NATO to limited, punctual and operational agreements instead of focusing on a broader institutional partnership [START_REF] Howorth | OTAN et PESD1: complexités institutionnelles et réalités politiques par Jolyon Howorth[END_REF]. They analyze the blocking power of Turkey in developing the relation further but also point to misleading assumptions about such a relation. Three implicit statements are especially analyzed : a) the alleged increasing similarity and proximity between the EU and NATO; b) the "natural" partnership based on a clear division of labor and c) the dominant role of NATO (Howorth & Paroissien, 2009, p. 820). According to the authors, far from being only practical, these problems are fundamentally political and are linked to the diverging historical and political projects of both organizations, NATO being the one lacking a clear raison-d'être. Even if their work focuses on neglected factors, developments and an in-depth analysis of the relation are lacking.

Our analysis build on the excellent work done by Koops in his analysis of the influence of NATO on the EU [START_REF] Koops | NATO's Influence on the Evolution of the European Union as a Security Actor[END_REF]. His work has several merits. First of all, it focuses on the dynamics of the inter-organizational relations taking three interrelated domains into account: the institutional, the operational and the identity domain. Secondly, Koops looks for exhaustive explanatory factors at five interconnected domains : a) the international level (exogenous factors and shocks) ; b) the national level (preferences of the member States); c)the organizational level ; d) the individual level (role of key individual entrepreneurs) and e) the inter-organizational level (Koops, 2012, p. 157). Thirdly, Koops analyzes the changing role of NATO and the impact of its evolution on the inter-organizational relationship. NATO first acts as a model for the EU, then as an enabler and lately as a negative "other" leading to EU/NATO decoupling. Fourthly, Koops uses a theoretical framework drawing on insights from rationalist theory (to explain the impact of the preferences of States, at the national level) and sociological institutionalism (to explain inter-organizational mechanisms) [START_REF] Koops | NATO's Influence on the Evolution of the European Union as a Security Actor[END_REF]. Using such a framework is really convincing to analyze the changing nature of the relationship between NATO and the EU. However, the difference between NATO role as a model and as a enabler is not really clear and the analysis lacks some powerful explanations about the factors leading to a change in NATO's role towards the EU. The objective of the present paper is to complement Koops' research design using the tools and concepts of research on IORs in order to explain how the relations between NATO and the EU evolves, both due to States' changing preferences as well as to organizational developments.

Interorganizationalism: an emerging research program in IR

Even if inter-organizational cooperation is not a new phenomenon and enjoys a growing importance in international relations, it has remained surprisingly unnoticed by theoretically informed international relation scholars [START_REF] Biermann | Towards a Theory of inter-organizational networking. The Euro-Atlantic security institutions interacting[END_REF]. Traditional theories have been caught off guard by recent efforts of inter-organizational networking. This is not surprising as far as realists are concerned given that they disregard international organizations, claiming that they are only minor actors of the international system. It is more striking to note that institutionalists have neglected this phenomenon. It seems that the attention paid to the study of regimes has led several scholars to disregard the study of organizations as such [START_REF] Biermann | Interorganizational relations1: an emerging research program[END_REF]Reinalda & Verbeek, 1998). International relations theory will only start studying organizations with the neo-institutionalism and the seminal work of [START_REF] March | Rediscovering institutions: the organizational basis of politics[END_REF].

The few authors who have studied inter-organizational relations focus on the factors that enable the development of cooperation strategies between organizations or describe the different types of inter-organizational relations. These studies suffer from some limitations. First of all, they tend to neglect a key characteristic of IGOs, the major role of States in determining their behavior. Even if IOs enjoy a high degree of autonomy, States remain prominent actors in the international stage. Secondly, studies tend to exclusively focus on IORs at the headquarters level. They lack a field perspective and this is a severe limitation given that it is widely assumed that key challenges for IORs lie at the operational level (Interviews, 2013). Thirdly, research on IORs need to rely on a stronger empirical basis: factors identified remain highly theoretical and data is lacking on the concrete dynamics of IORs. Finally most studies have a descriptive scope and very few strive to develop a theory of inter-organizational relations in the security field.

Research in international relations mainly focuses on inter-organizational influence, work focusing on describing and explaining IORs are only emerging, as the increasing number of doctoral projects on this issue show. Some researchers focus on inter-organizational policy networks and on the internal characteristics of a network influence its capacity to build links with other organizations. Perkin and Court, in the literature review dedicated to organizational networks, cite ten factors that tend to increase the influence of inter-organizational network on public policy processes (clarity of the governance mechanisms, strength in number, representativeness, use of new technologies,…) [START_REF] Perkin | Networks and Policy Processes in International Development1: a literature review London[END_REF]. Sandström and Carlsson make the assumption that a direct causal link exist between the level of heterogeneity and integration of a network and its capacity of influencing other actors [START_REF] Sandström | The Performance of Policy Networks: The Relation between Network Structure and Network Performance[END_REF]. Hopkins argues that the essential role of epistemic community is linked to their consensus on the scientific method and data adopted in the reform of international food aid policies [START_REF] Hopkins | Reform in the International Food Aid Regime: The Role of Consensual Knowledge[END_REF]. Mendizabal and his colleagues from the Overseas Development Institute emphasize the key functions of inter-organizational networks (filter information, convene, amplify, invest/provide, build communities and facilitate). He also shows how privileging some functions over others can have an impact on the types of inter-organizational relations [START_REF] Mendizabal | Understanding Networks1: The Functions of Research Policy Networks[END_REF].

These studies focus on influence and advocacy processes but do not define the different types of inter-organizational relations. Moreover, they mainly deal with the definition phase of the public policy cycle and not on the modalities of interaction during the implementation phase. Some pioneer research to which the proposed research project seeks to contribute need to be mentioned. Gehring and Oberthür use the concept of jurisdictional deliminating to explain why organizations working in inter-connected fields do not meet each other [START_REF] Gehring | The Causal Mechanisms of Interaction between International Institutions[END_REF]. These authors acknowledge that mutual interaction movements can lead to cooperative clusters but their research -focused on institutional interaction-do not give explanations of cooperation dynamics which are different in scope [START_REF] Gehring | The Causal Mechanisms of Interaction between International Institutions[END_REF].

Jönsson, using the network analysis theory, has developed a complex theoretical model of inter-organizational cooperation. He states that both the nature of the issue concerned by cooperation (low politics VS high politics, actors dependency in this issue area) and the properties of the organizations engaged in the cooperative schemes (linking-pin organizations and inside them, boundary role personnel) play a role [START_REF] Jonsson | Interorganization Theory and International Organization[END_REF] . However his analysis lacks hypotheses on the conditions necessary for the development of such organizations.

Holohan is one of the few authors studying the mechanisms of inter-organizational cooperation in crisis-management operations. Her comparative analysis of interorganizational cooperation in two municipalities of Kosovo highlights a series of factors that can make cooperation possible (leadership, creation of a common organizational culture in a network organization, role of the information and communication technologies). However, she does not compare her findings with another case of intervention and has chosen a very specific case being the implementation of a transnational civil administration by the UN in Kosovo [START_REF] Holohan | Networks of Democracy. Lessons from Kosovo for Afghanistan, Iraq and Beyond[END_REF].

Biermann, Koops are also building an emerging research program aiming to fill the gaps between organization studies and international relations. Finally, Schemeil shows that cooperating with other actors is also part of the survival and adaptation strategies of IOs [START_REF] Schemeil | Bringing International Organizations in1: IOs as Adaptive Hybrids[END_REF]. With Eberwein, he develops a research design emphasizing several factors triggering inter-organizational cooperation. According to Eberwein and Schemeil, organizations survival is only possible if they adapt to their external environment. Willing to increase their performance, power and legitimacy, organizations have no choice but to cooperate. Such a cooperation lead to a growing institutionalization of the world, a perspective beyond the scope of the present research project [START_REF] Eberwein | Coalesce or Collapse: Mandate Enlargement and the Expansion of International Organizations[END_REF].

Inter-organizational relations seen by organizations studies

It is striking to note how scholars studying international organizations in the international relations field fail to build on the findings of organization studies [START_REF] Ness | Bridging the Gap1: International Organizations as Organizations[END_REF] . Inter-organizational relations between for-profit and non-for-profit organizations have long been a focus of organization studies researchers. Several handbooks dedicate space to the study of inter-organizational relations [START_REF] Baum | The Blackwell Companion to Organizations[END_REF][START_REF] Nystrom | Handbook of organizational design[END_REF]. The objective of our research is to study how the findings of this discipline can be applied to the analysis of IORs in international relations.

The analysis of IORs in organization studies mainly focus on describing the existing relations and analyzing their factors. Bish analyzes the relations between different governmental agencies and seeks to identify different modalities of IORs, based on the public choice theory [START_REF] Bish | Intergovernmental Relations in the United States1: Some Concepts and Implications from a Public Choice Perspectives. Interorganizational Policy Making[END_REF]. He distinguishes between cooperation -common action leading to mutual benefits for each parties -, collusion -cooperation leading to benefits for each parties but imposing costs on a third party -competition and coercion -the imposition of an organization's preferences on another organization using the threat of sanctions [START_REF] Bish | Intergovernmental Relations in the United States1: Some Concepts and Implications from a Public Choice Perspectives. Interorganizational Policy Making[END_REF].

Van de Ven and Walker focus on ad hoc mechanisms of coordination assuming that such informal relations are the embryonic stage of IORs. In particular they examine the leading role of an organization which mobilizes support from other organizations in order to implement its activities [START_REF] Van De Ven | The Dynamics of Interorganizational Coordination[END_REF]. Galaskiewicz analyzes in which domains IORs may develop. He identifies three key activities : resources allocation, advocacy and organizational legitimacy [START_REF] Galaskiewicz | Interorganizational Relations[END_REF]. For Hall, coordination only occurs when organization try to adapt to their environment. He defines coordination as "the extent to which organizations attempt to ensure that their activities take into account those of other organizations" and assumes that inter-organizational conflict may contribute to coordination. His work, based on the exchange theory developped by Blau, takes the degree of formalization of an IOR as a key factor to identify various modalities of IORs. He finds that IORs can be voluntary, mandated or under contract [START_REF] Hall | Patterns of interorganizational Relationships[END_REF].

Even if these works lay the foundation for the analysis of IORs, they remain mainly descriptive and do not explain why certain types of relations exist in some cases and not in others. One notable exception is Whetten. In his literature review, Whetten presents different approaches dealing with IORs and especially focuses on the factors and consequences of the coordination strategies between organizations [START_REF] Whetten | Interorganizational Relations1: A Review of the Field[END_REF]. The approaches he presents (public administration, marketing, economic and sociological approaches) seem well-suited to analyze inter-firm relations on the domestic scene but more research is needed to know if they can be applied to other fields. Whetten also describes the different forms IORs can take (dyads, organization sets, action sets and networks). In each case he identifies various factors such as interpersonal relationships in the case of dyadic linkages or the role of a focal organization in the case of organization sets. In reviewing the literature dedicated to actionsets, he highlights the importance of a) the number of organizations in the action set; (b) the extent to which a single powerful organization assumes a leadership role; (c) similarity in values and attitudes among the members; and (d) the impact of other action sets' behavior [START_REF] Whetten | Interorganizational Relations1: A Review of the Field[END_REF].

Other scholars have strived to develop a theory of IORs, seeking to identify their necessary antecedents, their factors but also their consequences.

Other factors have been identified by various scholars such as a) the organization size, type and age [START_REF] Blau | Interorganizational Relations of Nonprofit Organizations1: An Exploratory Study[END_REF], b) the importance of resource dependence and of the types of resources committed [START_REF] Edstrdöm | Alternative Explanations of interorganizationai Cooperation1: the Case of Joint Programmes and Joint Ventures in Sweden[END_REF][START_REF] Levine | Exchange as a Conceptual Framework for the Study of Interorganizational Relationships[END_REF][START_REF] Van De Ven | The Dynamics of Interorganizational Coordination[END_REF], c) domain similarity -also known as mandate overlap and defined as "the degree to which organizations have the same services, clients, and personnel skills", d) monitoring by a funding agency, e) norms of equity and reciprocity in the relationship, f) communication mechanisms [START_REF] Van De Ven | The Dynamics of Interorganizational Coordination[END_REF].

Finally some actors also focus on the paradoxical nature of the cooperative behaviors. Mitchell and Lewin in their longitudinal study of accounting firms network show that, even if networks can be first created to increasing the profits of each member, temptations are high to then use the collected information to compete with partners [START_REF] Mitchell | The Coevolution of Network Alliances: A Longitudinal Analysis of an International Professional NetworkNo Title[END_REF].

Taking international organization as organization

This research is part of an emerging research program focusing on the analysis of interorganizationalism between international organizations. Ness and Brechin paved the way for bridging the gap between IR and organization sociology in their seminal article in International Organization [START_REF] Ness | Bridging the Gap1: International Organizations as Organizations[END_REF].

We assume that, to analyze the behavior of international organizations, one need to take into account the fact that international organizations are "live communities interacting with their environments, and they contain members who seek to use the organization for their own ends, often struggling with others over the content and allocation of the product. These dynamics produce a distinctive organizational character over time" (Ness & Brechin, 1988, p. 247). However, intergovernmental organizations are distinct from other organizations by the key role States play in their functioning. We adopt the following definition of inter-governmental organization : "organizations whose members include at least three States, that develop activities in several States and whose relations between Members are clearly established by a formal inter-governmental agreement" [START_REF] Karns | International organizations. The politics and Processes of Global Governance[END_REF].

In order to take into account these two characteristics of international organizations, the analysis be built a theoretical framework using principal/agent theory (P/A) to analyze the delegation process giving birth to IOs, and open-system theory to explore the link between and organization's environment and its internal dynamics [START_REF] Handel | The sociology of organizations. Classic, contemporary and critical readings[END_REF][START_REF] Negandhi | Interorganization Theory[END_REF]. P/A theory has become a classic for scholars of international organizations, so that there is no need to present it again. Such a theory assumes that States act through IOs to reduce the transaction costs associated with cooperation by using a delegation mechanism [START_REF] Abbott | Why States Act through Formal International Organizations[END_REF]Hawkins, Lake, & Nielson, 2006;[START_REF] Nielson | Delegation to International Organizations: Agency Theory and World Bank Environmental Reform[END_REF]. These works explain how the creation of organizations rest on a delegation process between one or several principals (the creators) and their agent (the creature). Principals delegate competences in a contractual way and link this process with control and sanction procedures. However there is always a gap between the interests of the principals and the ones of their agent. Such a situation may lead to the empowerment of the agent and its uncontrolled autonomy (Hawkins et al., 2006). In our case, this theory will help us to analyze the impact of States preferences on IOs behavior but also the strategies put in place by IOs to develop an autonomous behavior.

This theory, coming from the field of economics has become more and more elaborated over time. One of the key works in agency theory is the one by Hawkins, Lake and Nielson (2006). This group of scholars especially highlights two central problems principals face when delegating competences to IOs. These issues are particularly relevant for our research. First of all, most of the time States need to find a common ground through negotiation before they mandate an agent. This is the "collective principals" problem. Then it is hard for States to conserve a common position, so that they tend to send divergent orders to their creature, the so-called "multiple principals" problem (Hawkins et al., 2006).

Generally, IOs act "on their own", as long as they produce policies that are consistent with the interests of their principals. Costs for controlling an agent are high, so most of the time principals are reluctant to interfere in their agent's behavior. The P/A theory also provides interesting insights about the autonomization of agents. Agents are hard to control for three reasons. First, they can hide information to the principals when such a revelation can have negative effects on the agent. Then, the agent can "do things behind a principal's back", fearing its behavior may be sanctioned. Third, powers delegated to the agent by the principal can be sued against the principals (Hawkins et al., 2006).

Since the interest of agents and the interests of principals always diverge, there will always be a risk of agency slippage. Ceteris paribus, agency slippage, the discrepancy between what the principal wants and what the agent does increase with the number of principals delegating. Coordination become increasingly difficult as the number of principals grows.

To complement this state-centric view that dominates the literature, we will rely on the opensystem theory. It is widely assumed that international organizations should not be considered as "closed system". On the contrary, they are open-system depending on a wide environment to survive. Open-systems theory comes from the natural science perspective and seeks to examine the organization's environment and its internal characteristics are related (Negandhi, 1969, p. 1). This broad school of thought gathers different theories such as resourcedependence theory, organization ecology, or neo-institutionalism (Handel, 2003, pp. 226-231).

Open-system theory has formed the corner-stone of the inter-organization theory in organization sociology, especially building on insights from resource dependence theory and neo-institutionalism. The proposed research will mainly use neo-institutionalism, given that it enables to focus on rational and non-rational aspects of an organization's adaptation to its environment [START_REF] Barnett | Rules for the World: International Organizations in World Politics[END_REF][START_REF] Di Maggio | The Iron Cage Revisited: Institutional Isomorphism and Collective Rationality in Organizational Fields[END_REF][START_REF] March | Rediscovering institutions: the organizational basis of politics[END_REF]. We assume that organizations are purposive actors. One of their key goals is to stay relevant in a changing environment. They will therefore enter in a relationship with another organization, if the benefits of entering such a relation outweigh the cost of loosing autonomy and managing the relations (Alter & Hage, 1993, pp. 36-37). However, their rationality is only bounded since they do not have access to perfect sources of information and because the environment constrains their behavior [START_REF] March | Rediscovering institutions: the organizational basis of politics[END_REF]. Key features of an organization's environment have been presented by Aldrich (1969, pp. 59-60). In the following description, dimensions of the environment have been dichotomized for the sake of clarity. Of course, a dichotomy represents the two extremes along which an environment's dimension evolves. 1) Stability VS instability: the degree of turnover in the elements of the environment (organizations, clients).

2) Homogeneity VS heterogeneity: the degree similarity between the elements of the populations dealt with.

3) Concentration VS dispersion: the degree to which the population dealt with is evenly distributed over the range of the organization's domain. 4) Rich VS lean environmental capacity: the relative level of resources available to an organization within its domain. Such a dimension can be conceptualized as the degree to which an organization has to expand its domain to obtain the resources it requires, either to achieve stability or growth. Rich environments mean more resources, but also more organizations seeking to access them. Lean environments can promote cutthroat competitive practices. 5) Domain consensus VS domain dissensus: the degree to which the organization's claim to a specific domain is disputed or recognized by other organizations (Levine and White 1981) This dimension can be conceptualized at the institutional and interorganizational field. Domain consensus is a dynamic concept: organizations try to capture a domain by differentiating themselves from other organizations with highly similar goals. The achievement of domain consensus requires negotiation, cooperation and conflict. 6) Turbulence VS placidness: the extent to which an organization's environment is subject to rapid change.

Di Maggio and Powell have provided a convincing description of how organizations strive to adapt to their environment. They distinguish three processes that are particularly relevant for our research. Their research starts from the observation that organizational fields tend to become increasingly similar over time. An organizational field, as in our case, the European security architecture emerges thanks to four interrelated processes: a) increased interaction among organizations in the field, b) emergence of dominant organizations and of patterns of coalition between organizations, c) organizations face an increasing flow of information to processed, d) development of a mutual awareness among the participants involved in the field (Di Maggio & Powell, 1983, p. 148).

Once structured, an organizational field evolved through the process of isomorphism. Isomorphism is defined as "a constraining process that forces one unit in a population to resemble other units that face the same set of environmental conditions". Three processes of institutional isomorphism can be distinguished each with its own antecedents: 1) coercive isomorphism 2) mimetic isomorphism and 3) normative isomorphism. Coercive isomorphism "results from both formal and in-formal pressures exerted on organizations by other organizations upon which they are dependent and by cultural expectations in the society within which organizations function". (Di Maggio & Powell, 1983, p. 150) Mimetic isomorphism is a response of organization faced with uncertainty. Organizations entering a new field, or developing new activities will copy the structure and functioning of organizations they deem successful (Di Maggio & Powell, 1983, p. 151). A third source of change comes from normative sources and is linked to the power of professions in a field. Professions tend to struggle to define the conditions and methods of work in a specific field. They seek to legitimate their primacy in a specific field (Di Maggio & Powell, 1983, p. 152) .

Such a theoretical framework enables to reach a fine-grained understanding of IORs mechanism given that it takes into account factors coming from different levels. The following table sums up the level and factors identified as key to explain the dynamics of IORs.

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Level Definition

International level

Dimensions of an organization's environments that constraints its behavior and creates adaptive pressures.

Member States / Principals level

The impact of the changing preferences of principals on an IO's behavior. States' preferences are highly influenced by factors situated at the international level. This level also includes the impact of the negotiations and power play between collective and multiple principals.

Organizational level

Rationally bounded adaptive strategies put in place by an organization to adapt to the pressures of the international and principals level. Inter-organizational level Impacts of factors situated at the international, principals and organizational levels on the relations between an organization and its counterpart

Research design

We assume that the relation between NATO and the EU evolves from institutionalized cooperation to rivalry due to factors situated at the environmental, member States and organizational levels. The hypotheses guiding the research focus on the various explanatory factors of this evolution.

Hypothesis 1: The institutional preferences of key States such as France, Britain and the US, partly determined by factors at the international level, evolved from a preference for NATO to an increased use of the EU capacities.

Hypothesis 2: Through institutional isomorphism and membership expansion, the EU became increasingly similar to NATO. Increasing domain similarity leads to a stronger competition between both organizations.

Hypothesis 3: The development of the EU capacities made the EU less dependent on NATO's resources, therefore leading to a greater autonomy of the EU Hypothesis 4: EU's autonomization leads to a greater decoupling with NATO, due to the absence of domain consensus.

Some key variables presented in the hypotheses need to be defined.

The dependent variable is the relation between NATO and the EU evolving along a continuum from competition to cooperation. We expect two different outcomes. A = NATO and the EU cooperate. B = NATO and the EU compete.

Competition consists either in the defense of an organization's mandate against alleged or real rivals, or in a unilateral strategy of mandate enlargement at the expenses of other organizations [START_REF] Eberwein | Coalesce or Collapse: Mandate Enlargement and the Expansion of International Organizations[END_REF]. Cooperation is not an easy concept to define; it is often used and misused as a "blanket concept", covering a wide range of diverse realities. Following the seminal work of Keohane, we define it in relation to two other concepts, harmony and discord. Harmony refers to a situation where the selfish policies implemented by one actor make automatically the other actors' policies easier [START_REF] Keohane | After Hegemony. Cooperation and Discord in the World Political Economy[END_REF]. On the contrary discord exists when actors' policies naturally tend to be concurrent. Harmony as well as discord does not suppose any deliberate actions from actors. On the contrary cooperation imply that organization mutually adjust their programs by a process of negotiation called "policy coordination". Cooperation is thus a deliberate choice of organizations that tend to act together. Contrary to other relations, cooperation needs to be perceived as a durable and iterative phenomenon.

Of course both phenomena are ideal-types used to test hypotheses. The reality is more nuanced with varying degree of cooperation and competition existing at the same time. Boundary-spanning individuals are individuals who engage in networks tasks and employ methods of coordination and task integration across organizational boundaries (Alter & Hage, 1993, p. 46).

Domain

Resource dependence: two organizations can be dependent in terms of a) financial resources, b) human resources, c) competences, d) expertise, e) legitimacy,f) power/influence. Domain consensus refers to the degree to which an organization's specific goals are disputed, the compatibility of organizational goals, philosophy, reference orientations and goal overlap [START_REF] Levine | Exchange as a Conceptual Framework for the Study of Interorganizational Relationships[END_REF].

The research aims to identify the key factors that may explain the evolution from the situation A to the situation B. The following figure sums up our predictions.

Figure about here

The results presented here rely on the exploratory phase of the research. This phase consisted in the analysis of the literature and political documents dealing with the EU/NATO partnerships. Specific attention was paid to the in-depth analysis of the partnership agreements, of the political declarations on the EU/NATO partnerships but also on the analysis of both organizations' structures and field operations. Some 40 semi-structured exploratory interviews (in headquarters and in Kosovo) were also done in the framework of the doctoral research. Even if such interviews do not exclusively deal with EU/NATO relationship, they provide some relevant insights on the dynamics of IORs.

NATO and EU relationship 1989 -1999 : from indifference to the WEU "buffer"

During the Cold War, the relation between the EU and NATO was characterized by an absence of contacts. Both organizations had separate mandates and responsibilities. As a defensive alliance, NATO was in charge of ensuring the security of Western transatlantic allies through collective security mechanism. The principal threat to peace and security at that time was an attack from members of the Warsaw pact (NATO, 2006, p. 243).

At that time, the other organization acting in the field of Western European security was the Western European Union (WEU). The WEU had only a limited role, focusing on post-war arms control arrangements in Western Europe. This situation does not mean that the issue of burden-sharing on European security between European and American allies was not addressed. The question was only dealt with at a political, bilateral level between European States and the US with the overarching goal of reassuring the US on the EU members' commitment to their own security.

The situation of the Cold War can be analyzed with the notion of organizational field pointed out by Di Maggio and Powell [START_REF] Di Maggio | The Iron Cage Revisited: Institutional Isomorphism and Collective Rationality in Organizational Fields[END_REF]. The absence of contact between the EU and NATO prevents the structuration of the EU security architecture as an organizational field. Both organizations evolve in different environments, and have dissimilar domain. Even if they share beneficiaries, the mandate and philosophy of both organizations differ a lot.

In the 1990, the need for a greater implication of European countries to ensure their own security emerged. Two key external shocks played a role in this process.

Firstly, the end of the Cold War raised the issue of the usefulness of NATO, given the disappearance of a hegemonic threat. Some US policy-makers fear that dissolving NATO will lead to the resurgence of inter-state rivalries and war in Europe. At the same time, the need to share the economic burden between Europe and North America became even stronger (NATO, 2006, p. 244). Secondly, the inability of the EU to act to prevent and manage the wars in the Balkans was a trauma for the EU. The crisis revealed the gap between a European far-reaching economic power and its inability to back up diplomatic commitment with a powerful stick such as a credible military might.

To avoid US, UK and NATO officials' opposition towards a stronger political EU, the choice was made to develop a common foreign and security policy under the umbrella of the WEU. The Treaty of Maastricht tasked the WEU implement the decision having defense implications. The Treaty of Amsterdam further reinforced this decision. In its article 17, the Treaty stated that "The Western European Union (WEU) is an integral part of the development of the Union providing the Union with access to an operational capability" (European Union, 1997) and enumerates the so-called Petersberg tasks, defining the scope of EU actions in crisismanagement operations. These tasks include "humanitarian and rescue tasks, peacekeeping tasks and tasks of combat forces in crisis management, including peacemaking"(European Union, 1997, Article 17.2).

Two clear limitations were put to the development of the EU capacities. First of all article 17 paragraph 3 states that "the Union will avail itself of the WEU to elaborate and implement decisions and actions of the Union which have defense implications", even if the possibility of a future integration of the WEU into the European Union was foreseen. Secondly, the need to ensure compatibility between NATO and the ESDP is also clearly stated in the Treaty.

At the same time, the NATO Summit in Brussels in 1994, and the Final Communiqué of June 1996, confirmed by several following decisions, developed practical arrangements for NATO to support the WEU operations (NATO, 2006, p. 244).

Several authors considered the WEU as a "buffer" during the first phase of the EU/NATO relationship [START_REF] Hunter | The European Security and Defense Policy. NATO's Companion or Competitor1? Rand Europe[END_REF]. The development of the EU military capacities was a sensitive and politically risky process; therefore the WEU first keeps NATO and the EU at distance.

The use of the WEU was a compromise between the pro-Europeanists and the pro-Atlanticists: it enables to development of the EU capacities, without undermining NATO's primacy. Even if EU's domain started becoming closer to NATO's one, the mediation role of the WEU prevents the developments of contacts (and confrontation) between both organizations.

The development of the ESDP architecture: taking NATO as a model

The British-French Summit in Saint Malo, in December 1998, paved the way of the structuration of the European security field as an organizational field. Key to this development was the changing preference of the UK, evolving from an exclusive support to NATO to the recognition of the role the EU could play in European security. Moens argues that UK backed Saint Malo for two reasons. First British leaders felt frustrated by the EU's shortfall in the Balkans. And secondly, it appears that the US leadership in Kosovo was considered as rather weak and single-minded (Moens, 2003, p. 69).

The Saint Malo declaration provided the basis for the development of the ESDP capacities in several ways. First of all, it states the need for the European Union to "be in a position to play a full role on the international stage. This means making a reality of the Treaty of Amsterdam" (Rutten, 2001, p. 8). French and British pushed for a rapid implementation of the Treaty of Amsterdam. Secondly, for the first time the mention of an EU autonomous capacity, backed up with a consistent and credible military commitment is mentioned (Rutten, 2001, p. 8). However, the declaration also reasserts the primacy of NATO in the European Security architecture, stating that the EU will act in situations where the Alliance is not deployed and that the development of the EU capacities must not duplicate NATO's assets (Rutten, 2001, p. 9). The reaction of the US to the sea change of their British ally, was unambiguous with the famous 3Ds declaration of the US Secretary of State, Madeleine Albright : "As European look at the best way to organize their foreign and security policy cooperation, the key is to make sure that any institutional change is consistent with basic principles that have served the Alliance partnership well for 50 years. This means avoiding what I would call the Three Ds : decoupling, duplication and discrimination" (Rutten, 2001, p. 11).

NATO's reaction was also made explicit at the Washington Summit in April 1999. Even if the Alliance welcomed the recent new impetus for EU's foreign and security cooperation, the Allies reasserted that "the Alliance remains the basis for our collective defense" (Rutten, 2001, p. 20). But the declaration also contains a number of warnings for EU member States. Firstly, NATO and the EU should "ensure the development of effective mutual consultation, co-operation and transparency, building on the mechanisms existing between NATO and the WEU". Then Non-EU countries should be involved as fully as possible in future EU-led operations. And lastly, arrangements shoud be deviced in order to ensure that the implementation of the concept of "separable but not separate NATO assets and capabilities" but also to enable the EU to "have access to collective NATO assets when acting in crises where NATO is not deployed" (Rutten, 2001, p. 22).

In the meeting of EU leaders in Cologne in June 1999, EU Member States reaffirm the need to link ESDP development and NATO role as the key provider of security in Europe. Other reassurances will be empahized in Helsinki and Nice.

During the European Council Meeting in Helsinki in December 1999, EU leaders agree on fixing Headline Goals for the development of EU military assets. These goals focused on three key issues : a) readily deployable military capabilities and collective capabilities roles in the field of command and control… to carry out the Petersberg tasks ; b)the creation of new political and military bodies within the Council, c) the agreement on principles to ensure non-EU NATO countries' participation in EU-led operation "without prejudice to the European Union's decision making autonomy" (Rutten, 2001, p. 85).

The development of the EU capacities led to the transfer of the WEU capacities to the EU at Helskinki and at the WEU Council Ministerial Meeting of 2010. From 1999 to 2010, the WEU was reduced to a small strucutre and secretariat. The Treaty of Nice in 2001 provided the EU with the political framework for military operations and a permanent political and military structure.

The time period spanning from Saint Malo to the Helsinki meeting was really limited. In less than one year, the EU officials were supposed to design effective institutions for the ESDP with ambitious goals. The pressure from member States was high: the EU had no choice but succeed, without undermining the transatlantic partnership. For the organization, this new environment was characterized by instability, turbulence, uncertainty and limited resource.

The EU has no experience in the security realm. After the Balkans faux-pas, its credibility on the international stage was quite low and resources to develop new capacities, limited given the need to avoid duplication and decoupling with NATO. As noted by Koops, the recommendations provided by Javier Solana to Major General Graham Messervy-Whiting in designing the institutions was quite clear " the ESDP had to be up and running as quickly as possible and the approach had to be above all, highly pragmatic" (Koops, 2012, p. 159).

Given such pressures from the environmental level, the EU naturally turned to NATO for inspiration and advice. NATO was perceived as a successful military organization for the EU officials. In the emerging European security organizational field, NATO was dominant. These factors encourages the EU to use a strategy of mimetic isomorphism (Koops, 2012, p. 159).

One only needs to look at the similarity between the NATO's military principal military bodies and the EU's military staff and the EU military committee.

First of all, the EU military Committee can be regarded as a transposition at the EU level of the NATO military Committee. Both structures gather the Chiefs of Defence of Member States Countries. Meetings are also frequently organized in both organs at the level of the permanent Military Representatives. The aim of the EU and NATO military Committee is to provide guidance and advices on military matters to the Political and Security Committee of the EU council on the one hand and to the North Atlantic Committee on the other hand (EEAS, 2010a; NATO, 2012a).

The EU Military Staff and NATO International Military Staff also share a number of similarities. Both organs are placed under the supervision of the Military Committee. They are in charge of providing military expertise to the Committee and to ensure that military assets and resources are made available for the decisions taken by the Military Committee. Both organs liaise with civilian experts (EEAS, 2010b;[START_REF] Nato | The International Military Staff[END_REF].

Discussions between the EU military Staff and NATO international military staff are obviously made easier by the fact that both organizations share the same working processes and organizational structures.

Another source of isomorphism was normative. The military community played a key role on shaping the ESDP institutional structures. As always remembered by military officials, the same troops serve both in NATO's and in EU's missions (Interview, 2012). The military profession in Europe also shares common experiences, values and standards, linked to a similar training but also to the deployment in NATO transnational operations. Soldiers therefore act as key boundary-spanners between NATO and the nascent EU institutions. A NATO-inspired military community existed well before the ESDP, explaining that NATO has been influential in transmitting norms of professionalism, a common corpus of military doctrine, in promoting interoperability and in minimizing the fear of shared multinational command structures (Koops, 2012, p. 160).

One should also not forget that 11 out of the 15 Member States of the EU also belonged to NATO in 1999. Therefore, when trying to develop institutions for the ESDP, the member States referred to the only common experience they had on this topic. And this experience took place under the framework of NATO. Assuming that principals mandate their agents in a way that best serve their interests, it is also important to look at the negotiations occurring between the collective principals of the EU. The agreement of pro-Europeanist States on the use of NATO as model was also a strategy to gain the support of UK and other pro-Atlanticists States, for which the development of EU autonomous capacities was a red line that should not be crossed. Pro-Europeanists member States could also not afford the opposition of the US. (Koops, 2012, p. 162).

Developing the cooperation with NATO was also a mean for principals to limit the power of another agent, the European Commission. At that time, EU external policy was mainly led by the European Commission, which is at the heart of the EU "civilian power" [START_REF] Bull | Civilian Power Europe: A contradiction in Terms?[END_REF][START_REF] Manners | Normative Power Europe: A contradiction in Terms[END_REF]. Choosing to develop EU's military and defense capabilities within the Council, was a mean of preventing any influence of the Commission in the process. It was also a reminder of the principals that they keep a central role in EU's external policy, and that the appetite was strong for an inter-governmental ESDP (Koops, 2012, p. 162).

Another organization factor playing a key role in strengthening EU/NATO cooperation was the role of Javier Solana, acting both as an organizational entrepreneur and as a boundary spanner between EU and NATO. Solana previously served as NATO's Secretary General before being appointed High Representative for Foreign and Security Policy. Therefore he was not perceived as a threat for NATO's officials who know him quite well. Solana appointed Major General Graham Messervy-Whiting to design the new institutions of the ESDP, who have a strong NATO'experience. Given the limited time they have to succeed, they chose not to reinvent the wheel and draw heavily on NATO to develop the EU documents, architecture and doctrine.

The development of the EU/NATO relationship is therefore linked to a number of key factors. First of all, instances of normative and mimetic isomorphism lead to an increased domain similarity between the EU and NATO. Domain consensus was also high given that it was agreed that NATO is the main security provider in Europe and given that the EU took NATO as a model to develop its own vision of crisis management. Boundary spanners play also a key role in strengthening the links between both institutions.

Berlin Plus: affirming the ESPD dependence and NATO and NATO primacy

The development of the ESDP, copying NATO's structure and respecting NATO's primacy enable both organizations to institutionalize their partnership.

Everything starts with an exchange of letter between the NATO's Secretary General and the EU Presidency in January 2001 to define the scope of cooperation and the modalities of consultation and cooperation on questions of common interest relating to security, defense and crisis management (NATO, 2006, p. 247). These issues have always been central for NATO that seeks to stay the more relevant player in European security. The habit of having joint North Atlantic Committee /Political and Security Committee joint meetings developed as a "normal feature of cooperation between both organizations" (NATO, 2006, p. 247).

Cooperation increased after 9/11. Here again facing with a major external shock, and being uncertain about how to face it, EU officials invited NATO Secretary's General was invited to take part in the deliberation of the EU General Affairs Council in order to help them analyzing the situation. In the Prague Summit of November 2002, NATO officials reaffirm the need for cooperation (NATO, 2006, p. 247).

Cooperation became institutionalized with two key documents. First of all, the EU/NATO Declaration on the ESDP emphasized some key principles on which the EU/NATO partnership should be based. What is interesting in this document is how it paved the way for a partnership based on NATO's primacy. Before welcoming the ESDP developments, both organizations recall " the continued important role of NATO in crisis-management and conflict prevention" and "reaffirm that NATO remains the foundation of the collective defense of its members" (NATO & EU, 2002). The new role of the EU in the security realm is also seen as a way to contribute to the vitality of the Alliance (NATO & EU, 2002). The key principles of the partnership acknowledge the different nature of both organizations and the need for respecting EU's and NATO's autonomy and interests while at the same time calling for a mutually reinforcing action of both institutions. To make this partnership concrete, the EU agrees in involving the fullest possible the non-EU NATO members in the ESDP whereas NATO commits in supporting the ESDP with relevant decision and with ensuring access to NATO planning capacities (NATO & EU, 2002) .

The EU/NATO declaration of ESDP paved the way for the institutionalization of a permanent partnership between both organizations. Such a partnership took the form of a practical contractual arrangement, the Berlin Plus Agreement, defining the scope and mechanisms of cooperation between both organizations. Unfortunately, scholars can only rely on the information provided by the EU and NATO, given that the document itself is classified. These permanent arrangements were finalized in The main elements covered by the Berlin Plus Agreements are:

-Assured access to NATO planning capabilities able to contribute to military planning for EU-led operations; -The presumption of availability to the EU of pre-identified NATO capabilities and common assets for use in EU-led operations; -Identification of a range of European command option for EU-led operations, further developing the role of NATO's Deputy Supreme Allied Commander Europe (DSACEUR) in order for him to assume his European responsibilities fully and effectively; -The further adaptation of NATO's defence planning system to incorporate more comprehensively the availability of forces for EU-led operations; -A NATO-EU agreement covering the exchange of classified information under reciprocal security protection rules; -Procedures for the release, monitoring, return and recall of NATO assets and capabilities -NATO-EU consultation arrangements in the context of an EU-led crisis-management operation making use of NATO assets and capabilities" (NATO, 2006, p. 249).

The Berlin Plus presents advantages for both parties. It ensures that the EU can rely on the NATO resources for its own operations while at the same time; it enables NATO to keep an eye on ESDP developments and to stay the most relevant actor in European security. The partnership is therefore highly asymmetric, acknowledging the primacy of NATO and the dependence of the EU. This agreement can be seen as a compromise to have US and UK support to ESDP development. At the time, it leaves enough room of maneuver for pro-Europeanists States and the EU, especially at the operational level.

The operationalization of Berlin Plus: NATO/EU co-operation in the Balkans

In order to understand how the relationship between NATO and the EU evolved, it is worthwhile to analyze how co-operation develops at the operational level and not only at the headquarters level.

If 1999 and 2000 have seen the building of the ESDP institutions and the development of its structure and doctrine, 2003 is the year of the birth of the EU as an external actor. The Balkans were a highly symbolic theater of operations for the EU. The objective of EU intervention was first of all to restore the EU's image and credibility. The stakes of the operation were therefore very high. The EU could not afford to lose face again. The operationalization of Berlin Plus agreement occurs with the operation Concordia in Macedonia and Althea in Bosnia Herzegovina. However both missions occur in totally different contexts. During Concordia, the EU was in a dominated position, unsure of its own capabilities and strongly dependent on NATO. On the contrary, during Althea tensions started emerging.

The Concordia mission launched in March 2003 lasted 9 months. The aim was to take over NATO mission and at the request of the government of the Former Yugoslav Republic of Macedonia (FyROM). The EU was tasked to create a stable secure environment to allow the implementation of the August 2001 Ohrid Framework Agreement (European Council, 2003).

The NATO's DSACEUR had a double-hatted position, being at the same time the EU's Operation Commander. NATO provides essential planning resources such as 15 trained officers at the SHAPE to command the mission. In Naples, the EU command element was a liaison cell between DSACEUR and the EU Force Commander in Macedonia (Koops, 2012, p. 163). It was decided that France would be the framework nation, a concept strongly influenced by the practices of NATO's operations. Each NATO mission has a framework nation in charge of organizing operational command. In 2002, the EU endorsed the framework nation concept, as a basis for the development of autonomous EU-led operations.

The first EU commander was therefore French.

In terms of human resources, the EU drew on a pool of soldiers who were before deployed within the alliance in the Operation Allied Harmony in Macedonia. Being deployed for the first time in a EU mission, the military came back to what it knows and uses the deployment in NATO's missions as a model. At the individual level, the inter-personal relations between Javier Solana and NATO Secretary General, George Roberston is widely assumed to have been excellent. Both persons work in a co-operative spirit, exchanging information and fostering mutual understanding (Koops, 2012, p. 163).

The dependence of the EU on NATO during Operation Concordia is the results of several factors. First of all, it is strongly associated with the nature of the Berlin Plus arrangements, being an asymmetric partnership. It could also be considered as a case of coercive isomorphism [START_REF] Di Maggio | The Iron Cage Revisited: Institutional Isomorphism and Collective Rationality in Organizational Fields[END_REF]. The EU exclusively depends on NATO for the provision of human, logistic, planning resources as well as in terms of legitimacy. As stated earlier, EU and NATO draw on the small pool of professional soldiers. Then all the planning and logistic capacities were given by NATO according the Berlin Plus arrangements. More importantly, the EU depends on NATO for its legitimacy and credibility. Because of its failure to act at the beginning of the crisis, the EU was entitled with a very low level of trust within the population in the Balkans. It is still the case today even in Kosovo where KFOR enjoys a very high level of popularity whereas the EU mission, EULEX is rejected by the population. The EU officials put a lot of efforts in designing public communication campaign aiming at convincing local populations as well as Member States public opinion of the fact that the EU Concordia was a twin operation of NATO.

According to the EU military staff, Concordia was an ideal mission to test Berlin Plus and to gain confidence for the EU (Koops, 2012, p. 170). The security risks were very low given that the tough job had been done by NATO. In cases of violence escaladation, NATO missions in Macedonia and Kosovo could provide emergency support to the EU.

Concordia paved the way for a more ambitious operation. EUFOR Althea was the second and last implementation of Berlin Plus. The mission was launched on 2 December 2004, and results from the handover of NATO's SFOR mission to the EU under the terms of the Berlin Plus agreements. The mission was authorized by the UN Security Council (UNSC) resolution 1575. The mandate of the (still ongoing) mission is "to support Bosnian institutions to maintain a safe and secure environment in BiH" and "to provide capacity-building and training support for the Bosnian Ministry of Defence and Armed Forces" [START_REF] Eufor | EUFOR Factsheet[END_REF].

Contrary to what happened with Concordia, tension arose during Althea. France complained about the fact the US regional commander exercised too much control over Concordia. Therefore it was requested that an additional EU Commander be located in the NATO regional HQ at Naples. Of course, Britain strongly disagreed pointing at the crucial role DSACEUR played in Concordia's successes. A compromise was reached with the creation of new decision-making body: the EU Special Representative to the EU High Representative.

The absence of synergy between NATO and the EU became quite explicit with these different layers of authority and chains of command.

The first phase of NATO-EU relationship was thus characterized by an institutionalized cooperation partnership due to the following factors. Firstly, the use of NATO as a model for the development of the ESDP enables both organizations to share a moderate level of domain similarity. 11 out of the 15 EU member States are also NATO members and both organizations aimed to preserve European security. However NATO had a military and defence identity whereas the EU has a civilian culture. The relation was also characterized by its asymmetry: the EU strongly depends on NATO to act at the operational level. The EU lacked experience, planning capacities, and legitimacy to be considered as an autonomous actor. The relation was also characterized by a degree of domain consensus: NATO primacy was accepted and acknowledged and both organizations agreed to rely on NATO philosophy and way of doing things in crisis-management. Finally, principals expressed clear preferences for an ESDP controlled by NATO.

In such a context, how can we explain the evolution of the relation between both organizations? Explanations are to be found in the evolution of the key determinants of the relation: domain similarity, domain consensus and interdependence as well as in the changing preferences of Member States.

The autonomization of the ESDP

In order to explain the changing nature of EU/NATO relationship we will use the concept of autonomization defined by Koops as : "a process in which an inter-governmental organization can change or increase its status of autonomy and is able to decide and act without interference from other actors" (Koops, 2012, p. 174). The EU autonomization process was twofold. First of all, the EU asserted its role as a major crisis-manager against the will of some of its principals but with the support of pro-Europeanists principals. This is a typical case of problems arising when "multiple principals" defend differing preferences and send contradictory signals to their agents (Hawkins et al., 2006). Secondly, the EU developed autonomous with regards to its mentor, NATO.

EU's autonomization is closely linked to its enhanced credibility in the international stage, a result of what Solana called "legitimacy by action" (Koops, 2012, p. 173). In order to gain legitimacy, the EU needed to act autonomously in order not to be only perceived as depending on NATO to succeed. The operationalization of the ESDP has provided Europeanists/autonomists countries with new channels, institutions and opportunities to defend an autonomous development and use of the EU assets. Interests of pro-Europeanists principals coincided with the interest of their agent. In the process, NATO appears as an obstacle and even a competitor. In 2003, pro-Europeanists sought to create an EU's dedicated military HQ. This step was perceived as crossing the red line for the US and the UK. Tensions between the principals were high. After the strong disagreements on the war in Iraq, France, Germany, Belgium and Luxembourg pushed for an independent EU HQ.

A compromise was reached with the establishment of an EU cell within NATO SHAPE and a small civil-military cell at the EU's military staff for the planning of pure EU civil-military mission. Even if NATO saw this as way to avoid duplication in the realm of NATO pure military affairs, it will also become a way for the EU to break its dependence on NATO and to assert its identity as a "comprehensive" crisis-manager. This will be the start of a long series of clashes between the former partners both at the institutional and at the operational level.

At the institutional level, the civ-mil cell was tasked to develop an EU Operation Center. The objective was not only to integrate military aspects into civilian missions but to develop autonomous EU military capacities (Koops, 2012, p. 175).

In the military realm, NATO faced a serious blow for its credibility in 2007. In November 2003, France and Great Britain launched the EU Battlegroup initiative. The Battlegroups are part of the implementation of the defence aspects of the 2003 European Security Strategy and are regarded as an an integral part of the new Headline Goal 2010 (that follows on from the 1999 Helsinki Headline Goal) (European Parliament, 2006). They therefore naturally emanate from the Saint Malo Declaration.

The Battlegroup Concept consists of "highly trained, battalion-size formations (1,500 soldiers each)1 -including all combat and service support as well as deployability and sustainability assets. These should be available within 15 days notice and sustainable for at least 30 days (extendable to 120 days by rotation). They should be flexible enough to promptly undertake operations in distant crises areas (i.e. failing states), under, but not exclusively, a UN mandate, and to conduct combat missions in an extremely hostile environment (mountains, desert, jungle, etc). As such, they should prepare the ground for larger, more traditional peacekeeping forces, ideally provided by the UN or the Member States" (European Parliament, 2006, p. 5). This description of the Battlegroup clearly points out that they are a military resource for "standalone" operation by the EU. In November 2003, Germany and even Sweden, a neutral State, agreed to support this initiative.

One year later, NATO announced its own plan to develop a NATO Response Force (NRF) at the Prague Summit in November 2002 dedicated to NATO's transformation. NRF are said to be "at the centre of NATO's transformation" (NATO, 2013). The description and mandate of the force are highly similar to the ones of the EU's Battlegroups. It is an "highly ready and technologically advanced multinational force made up of land, air, maritime and special forces components that the Alliance can deploy quickly wherever needed". Such a force "has the overarching purpose of being able to provide a rapid military response to an emerging crisis, whether for collective defence purposes or for other crisis response operations. The force gives NATO the means to respond swiftly to various types of crises anywhere in the world" (NATO, 2013).

Both schemes are supposed to be mutually reinforcing since they build on the same set of resources. However in 2007, NATO was forced to announce that it cut down the level of ambition of the NRF. For the first time an EU body was preferred by the principals.

Another factor led to an increased domain similarity between NATO and the EU: both organizations engage in a process of membership expansion, covering the same geographic area. However the issue of Turkey a NATO member, tired of waiting for EU membership further complicates EU/NATO discussion. Most of the people assumed that the future EU/NATO co-operation depends on the easing of the tensions between Cyprus, Greece and Turkey (Interviews, 2013).

The autonomization of the EU led to an increased domain similarity between both organizations. Both have ambitions in the defence and the military realms. Through membership expansion, both organizations have an increasing number of similar beneficiaries. One just needs to look at the European Security Strategy and at the NATO Strategic Concepts to conclude that both organizations have a similar if not an identical domain. The analysis of the external security environment is the same for both organizations, mentioning terrorism, proliferation of weapons of mass destruction, regional conflicts and state failures as key threats. Both organizations aim to be the key player in ensuring collective security and in crisis-management (European Union, 2003;NATO, 2010).

From Artemis to the Horn of Africa: the end of EU dependence on NATO At the operational level, the process of autonomization of the EU led to a decoupling from NATO.

The process started with the French-led operation Artemis. The French pushed for an EU Operation in the Democratic Republic of Congo (DRC) in support to the UN. Initially, informal talks between the UNSG, Kofi Annan and President Chirac paved the way for the deployment of a French operation, named Mamba. However President Chirac soon realized that such an operation could be a ideal case to prove that the EU was capable of deploying an operation without NATO's support (Kees, 2007, p. 156). The europeanized mission was recalled Artemis and provided with a UNSC mandate aiming to "contribute to the stabilization of the security conditions and the improvement of the humanitarian situation in Bunia, to ensure the protection of the airport, the internally displaced persons in the camps of Bunia and, if the situation requires it, to contribute to the safety of the civilian population, United Nations personnel and the humanitarian presence in town" (Kees, 2007, p. 152). French soldiers made up 90% of the forces deployed and the operational headquarters were based in Paris, gathering some 80 European officers.

US and NATO officials openly complain that this operation violated the spirit of the Berlin Plus agreements, given that NATO had not been consulted. Before the operation started, French informally asked the US about the possibility for a strategic airlift for the EU troops, but the US suggested that such an asset borrowing issue was to be discussed under Berlin Plus. France therefore turned to Ukraine (Koops, 2012, p. 176).

Even if limited in time and scope, Artemis was significant in many ways for the NATO/EU relationship. The impact of the EU as such is rather limited given that Artemis is more regarded as a French mission with an EU cover. The fact that the mission heavily drew on French planning capacities and assets had not make possible to test all the EU rapid response mechanisms. The major impact it has had was in changing the focus of EU partnership from NATO to the UN. Artemis is a successful example of partnership between the UN and regional organization. It has enabled the UN to prepare the transition from peacekeeping to peace enforcement better in a situation characterized by continuing violence and the absence of any peace to be kept. Direct reporting from Solana to New York worked better than reporting mechanisms used in Kosovo or Afghanistan. One of the key objectives of the mission was to ensure the continuous delivery of humanitarian aid. According to the humanitarian community and to ECHO, the relation between the military and the humanitarian actors went well (Kees, 2007, p. 157). This is a strong contrast with the violent critics expressed by the humanitarian community about the instrumentalization of humanitarian actors by NATO in Afghanistan. Another clash occurred about the issue of who will be providing an airlift to the African Union in 2005. After 3 months of struggle, both organizations decided to undertake separate missions (Koops, 2012, p. 177). Tensions at the operational level are closely linked to the end of the dependence of the EU on NATO. The EU can now afford to launch its own missions. At the individual level, Solana's relation with the new NATO SG, Jaap de Hoop Schaefer, was far less effective and further complicated the relation. Increased domain similarity and absence of interdependence are key factors to explain the development of EU/NATO rivalry.

Interventions in the

The fight for becoming the UN favorite peacekeeper

A last factor that explains the evolution of the NATO/EU relationship towards manifest rivalry is the end of the domain consensus between both organizations. Domain dissensus gets stronger with the struggle of both organizations to be recognized as the only legitimate regional partner of the UN. The use of the concept of comprehensive approach by both organizations reveals their ambitions but is also at the heart of their competition.

The more similar the EU is to NATO, the more it seeks to differentiate itself to bolster legitimacy. An important aspect of this process is the rhetoric discourse about the uniqueness of the EU on the international stage. In the struggle to be recognized as the more legitimate regional peacekeeper, the EU has an asset. The EU is a more "comprehensive" organization than NATO. Its military power is complemented by civilian crisis-management tools, that have enhanced the credibility of the EU as a "soft power". For the time being this concept is not really concrete and it is mainly used to back discourse about EU uniqueness. A task force is working at the EU level to clearly define what the concept means. The Lisbon treaty has equipped the EU with all the tools needed for a comprehensive approach integrating diplomatic, economic, development and, in the last resort, military resources to address global challenges. For the EU, the main challenge lies in ensuring coordination and coherence between the various dimensions of its external action. The task is made complicated by the fact that the external policy has both a supranational and an intergovernmental character.

Inter-institutional rivalries between services are high. NATO's comprehensive approach is more oriented towards external partners. NATO has only limited capacities as a crisis-manager. It can only act in the military realm. The experience of the Provincial reconstruction Teams (PRTs) in Afghanistan and Iraq aiming both to win the population's hearts and minds and to develop NATO's capacities in the reconstruction realm have had mixed results. Humanitarian actors criticize such approach for blurring the lines between neutral humanitarian action, and political military mission [START_REF] Micheletti | Afghanistan1: gagner les coeurs et les esprits[END_REF]. More globally, the use of Afghanistan as a test case for its comprehensive approach has been met with limited successes and the organization suffers from an identity crisis. Recently, a new integrated center was created to provide NATO with civilian expertise and capabilities. The Comprehensive Crisis and Operations Center (CCOMC) is part of the SHAPE's transition program and aims to"to enhance [NATO] contribution to a comprehensive approach to crisis management, as part of the international community's effort, and to improve NATO's ability to deliver stabilization and reconstruction effects". [START_REF] Nato | New integrated NATO center supports the Alliance with improved approach to emerging security challenges and crisis[END_REF]. The organization still considers its strategic partnership has a way of developing a comprehensive crisis-manager identity but facts can hardly hide the intense rivalry between both organizations.

The UN will play a key mediating role in the NATO/EU relationship. It is clear that the EU invest a lot in its relation with the UN in order to be perceived as the only legitimate regional peacekeeper. Artemis was for sure a case in point and the EU is a key UN partner through the European Commission. The European Commission has developed several Memoranda of Understanding with various UN agencies and remains a major donor for the UN. But recent examples have show that it could also be convenient to use NATO as a military arm as the UN when facing a blocus in the United Nations Security Council. The recent operation in Libya has demonstrated that NATO is far for being dead. In Kosovo, KFOR remains a key actor for the stability of the region in a context where EULEX is not accepted by both the Serbian and the Albanian population.

NGOs, and especially humanitarian NGOs may also play a role in mediating the EU/NATO disputes. One of the key dilemmas in implementing the comprehensive approach is the humanitarian dilemma. In order to deliver aid and to be granted access to the population, humanitarian actors need to be clearly distinguished to political and military actors. In order to succeed in improving coordination between the actors involved in crisis-management, a sound comprehensive approach need to take into account this specificity [START_REF] Eide | Report on Integrated Missions[END_REF] As Afghanistan has shown, NATO is not well equipped to interact with civil-society organizations [START_REF] Micheletti | Afghanistan1: gagner les coeurs et les esprits[END_REF]. Several humanitarian actors point out that NATO does not understand the specific features of humanitarian action (resting on the principles of solidarity, neutrality, independence and impartiality). Some interviewees speak about a strong cultural difference and of the absence of a common language to create a basis for dialogue. (Interview, 2012). On the contrary, the EU appears as having far better relations with the humanitarian sector. DG ECHO, the office of the European Commission in charge of humanitarian aid and civil protection is regularly ranked as one of the best donors [START_REF]Humanitarian Response Index 2011[END_REF]. Experiences of civ-mil interaction in Artemis and EUFOR Tchad are widely recognized as best practices both by the humanitarian community and by the EU. The development of the EU comprehensive approach seeks to preserve the specificity of humanitarian aid, ECHO being the only external service of the Commission that is not integrated in the EEAS. Furthermore the European Consensus on Humanitarian Aid is widely recognized as an exemplary document to define the specificities of humanitarian action and to prevent any instrumentalization of humanitarian policies.

Conclusion

Using insights from the principal/agent theory and tools of the organizational sociology, this article seeks to explain why inter-organizational relations can evolve from co-operation to competition. Using examples of the institutional and the operational level, the research has identified some key international, member States and organizational factors that determine the EU/NATO relationships.

The first phase of the relation was characterized by a turbulent, unstable environment for both organizations. The end of the Cold war raised questions about the future of the European security architecture and the development of the ESDP was a rather sudden process. Needing to develop new capacities rapidly, the EU turned to NATO as a model. Through institutional isomorphism, the EU developed an ESDP identity similar to NATO. Domain similarity was increased by the fact that both organizations share the same principals and drew from the same pool of resources. Boundary-spanners such as Javier Solana or the European military played a key role in developing the partnership between both organizations. The relation was also highly asymmetrical: the EU depended on NATO for a wide range of resources (logistic, planning, human, legitimacy). The environment was also characterized by a high degree of domain consensus, the primacy of NATO not being challenged. During this period Member States' preferences were clearly oriented towards limited ESDP capacities, kept under NATO control to avoid duplication. Europeanists States saw this situation as transitional one, a compromise to get the support of the UK and the US to the development of EU's military capacities.

Few years later, the relation between EU and NATO considerably changed due to the combination of several factors. First of all the environment evolved towards more stability: it became clear that NATO would survive the end of the Cold War and that the EU will become a key security provider in Europe. However, crises in Africa, in Afghanistan and in Iraq create a high level of turbulence. Resources were more equitably distributed between both organizations, the EU being granted with performing military assets. Member States adapted to this new situation by granting new responsibilities to the EU. The interests of pro-Europeanists states (and especially France) coincided with the quest of autonomy of the EU. At the organizational level, the increasing similarity between NATO and the EU and the end of the EU's dependence on NATO led to a greater autonomy of the EU, being now able to unilaterally implement its security mandate. In reaction NATO sought to defend its own attribution. Rivalry began and was aggravated by the end of domain consensus. NATO is no longer perceived as the dominant partner: the EU is pointing at its uniqueness as a civilian and military crisis-manager able to cover crisis-prevention, crisis-management and reconstruction activities. The current rival development of EU and NATO comprehensive approach can be analyzed as a process to be recognized as the most relevant security provider in Europe. The UN as well as humanitarian NGOs will be key mediators in the process, since both could grant legitimacy to a regional peacekeeper.

Even if this study has identified some key factors explaining the dynamics of IORs over time, it suffers from some limitations. The results presented here rely on a single case study. Therefore further research will be needed in order to confront the hypotheses to new cases and new data. Moreover, it would be interesting to research if factors relevant for the analysis of dyads can be extended to the analysis of bigger organizational field. Then, the articulation between the three levels mentioned (international, principals and organizational levels) need to be further elaborated, in particular to assess the channels of influence of each level on an organization's behavior. These issues will most probably be addressed in the framework of the doctoral research of the author.

  similarity refers to the extent to which organizations share constitutive elements (it is linked to the homogeneity of an environment. Aspects of domain similarity are: a) general and specific objectives of an organization, b) beneficiaries/clients c) expertise, d) issue area, e) ethics and values and f) sources of funding/donors.

  [START_REF] Eunavfor | EUNAVFOR website[END_REF] called Berlin Plus after 1996 Berlin Summit considered as the start of the WEU/NATO cooperation (European Security and Defence Assembly & Assembly of the Western European Union, 2003). The filiation is quite clear: the EU the EU is as dependent to NATO as the WEU was and it is assumed that the EU will only play a limited role in European security.

  Horn of Africa further lay the ground for manifest EU/NATO rivalry. NATO handed over its first anti-piracy mission to the EU in December 2008. The EU thus launched its mission EUNAVFOR Atalanta aimed to "deter, prevent and repress acts of piracy and armed robbery off the Somali coast. EU Naval Force protects vessels of the World Food Programme (WFP) delivering aid to displaced persons in Somalia and the protection of African Union Mission on Somalia (AMISOM) shipping" (EUNAVFOR, 2013).Operation Atalanta is considered as a success and as key part of the EU comprehensive approach to the Horn of Africa. In March 2009, NATO came back with the operation Allied Protector aiming "to assist in international efforts to deter, defend against, and disrupt pirate activities off the Horn of Africa"(NATO, 2009). Interviews with French military officers reveal that the comeback of NATO created obstacles for the fulfillment of the counter-piracy mission. European soldiers are not sure about what NATO is doing and some even think that NATO mission is no longer here, not knowing that NATO resumed its mission in 2009. Other military officials confessed being surprised to find more anti-piracy vessels than pirates to deter(Interview, 2013).

  The European External Action Service has been set up, gathering the Commission and the European Council services in order to promote synergy and unity of efforts between EU's services. It is led by the Baroness Catherine Ashton who is double-hatted as the High Representative of the Union for Foreign Affairs and Security Policy/Vice-President of the European Commission (HR/VP) (EEAS, 2010c).