Diplomacy, hybrid leadership, and EU actorness: assessing the role of EU High Representative Catherine Ashton in the 2013 Kosovo-Serbia agreement

Over the last decade, the role of the European Union (EU) High Representative (HR/VP) became increasingly salient. However, a systematic understanding of how this figure’s leadership shaped the character of EU diplomacy and actorness in peacekeeping is lacking. To address this issue, we analyse Catherine Ashton’s leadership (as the first HR/VP post Lisbon Treaty) in the 2013 Kosovo-Serbia agreement, a high point of her tenure. We argue that Ashton’s success is largely due to her hybrid leadership, alternating between transactional and transformational and capitalising on the EU’s presence and opportunities as an international actor. We propose the concept of hybrid leadership as an analytical tool and illustrate its relevance in an empirical case study. Our examination of Ashton’s hybrid leadership contributes to shedding light on the potential role of the future HR/VPs and on how these can reinforce EU leadership, diplomacy, and actorness, contributing to reinforcing the corresponding academic debates.

In addition to consolidating Ashton's and the EEAS's diplomatic credentials and potential, this case study is also relevant because, for a long time, it represented the most substantial step in the Serbia-Kosovo normalisation process despite Serbia's goal of being 'not so much normalisation and reconciliation in Serbian-Kosovar relations, but rather making progress with EU integration' (Szpala, 2016, p. 1;Economides and Ker-Lindsay, 2015). This matters because the 'normalization of relations with Kosovo is a prerequisite for Serbia for further progress on its road toward the EU' (Beha, 2015, p. 106) although 'the prospect of membership remained remote' for most of the process (Bieber, 2015, p. 292). Writing about the normalisation efforts remains as relevant today as it was in 2013, as steps like the reestablishment of direct flights between Kosovo and Belgrade after more than 20 years, or the USA-led economic normalisation agreementswhich might not have been possible without the agreement under analysishave recently been celebrated (Euronews 2 ; UN Security Council, 2020). Ashton's success (despite initial dissatisfaction and reluctance) and her 'soft' diplomacy emphasised the potential for this kind of leadership for the EU's external action and the post of HR and for the reinforcement of the EU's actorness.
Although Ashton's successor, Federica Mogherini, also played an active role regarding this matter, this article will focus on the 2013 agreement and on Ashton's role as the first post-Lisbon HR/VP, since 'an evaluation of Ashton's performance is a valuable exercise because her actions as first HR influenced the layout and perception of the office and are an indication of the development of EU foreign policy in general' (Helwig and Rüger, 2014, p. 2). This article goes beyond this argument by showing how Ashton's behaviour as HR/VP signalled important changes in the EU Foreign Policy and paved the way for deeper changes in the EU diplomacy and actorness in the Balkan region. Passing this 'first test' helped shape subsequent endeavours by the EU's diplomacy chiefs.
Considering that when she took office as the EU's first (post-Lisbon) HR/VP, Ashton was seen as inexperienced and lacklustre and her appointment was met with strong reservations and criticism, why and how did she succeed in mediating the 2013 Serbia-Kosovo agreementone of the (if not the) most crucial moment in the normalisation process in decades? The outcome of the peace process remains puzzling, and we argue the explanation partly lies in Ashton's hybrid leadership, which we will develop theoretically as an analytical tool and explore empirically through a constructivist theoretically oriented case-centric process tracing. Building on leadership and actorness research, this article uses this empirical case study to shed light on the significance of the HR/VP's leadership for enabling and reinforcing EU diplomacy and actorness. Although primarily focusing on the explainingoutcome process tracing (Beach and Pedersen, 2013), by combining theory-testing and theory-building elements, this article further contributes to broadening the leadership and actorness theoretical debates.
First, we contextualise the leadership debate and propose a conceptualisation of 'hybrid leadership'. Then, we analyse Ashton's hybrid leadership in the Kosovo-Serbia agreement starting with a chronologic contextualisation and systematisation of key events, leading up to the signing of the agreement. Subsequently, we analyse Ashton's actions and strategies in light of our hybrid leadership conceptualisation, while critically engaging with the scholarly debate on EU actorness to reinforce their interconnectedness. This allows us to reinforce the relevance of our conceptual and theoretical contribution considering the context-bound nature of the leadership process and to assess Ashton's hybrid leadership while shedding light on its role for enabling and reinforcing EU diplomacy and actorness. We finish with a discussion of the results and conclusion.

Theoretical perspective: hybrid leadership
In the international system, leadership is not necessarily consensual nor coherentand it is often confused with hegemony (Helms, 2014, p. 262)though it has been profusely explored by numerous scholars (E.g., Burns, 1978;Blondel, 1987;Young, 1991;Ikenberry, 1996;Underdal, 1998;Grubb and Gupta, 2000;Nye, 2008;Helms, 2014;Northouse, 2016;Vu, 2017;Harrison, 2018), and specific scholarly literature on EU leadership, in particular, has proliferated in recent years (Chaban et al., 2013;Héritier and Prakash, 2015;Van Esch, 2017;Virkkunen, 2018), with a particular proclivity for examining its role in the fight against climate change at the international level (Oberthür and Kelly, 2008;Wurzel et al., 2011;Oberthür, 2011;Lindenthal, 2014;Godzimirski, 2016;Skjaerseth, 2017;Parker and Karlsson, 2017). Generally, we can define leadership as a process through which an actor (either collectivelike a state or an organisation -, or individualacting alone or on behalf of a collective) musters material or ideational resources to guide or influence other actors to pursue mutual goals (Vu, 2017, p. 2). The leader status thus implies a logic of reciprocity, shared goals between the involved stakeholders, and a performative acquiescence and validation of the leader's legitimacy on behalf of those who follow him/her. In this article, we look at the HR/VP's actions to ensure such acquiescence and validation in the context of her diplomatic efforts to secure the 2013 Serbia-Kosovo agreement.
The relevance of analysing the leadership of the first HR/VP is crucial for understanding the potential of this interinstitutional figure in the future in similar settings. The circumstances of our case study are especially relevant: a low-profile figure that assumed an increasingly salient position in the EU Foreign Policy by achieving unexpected success in an especially challenging scenery that is, simultaneously, strategic for the EU. Ashton's leadership as HR/VP set the precedent for understanding the current and future dilemmas and opportunities for the post of HR/VP in the midst of significant changes in the EU foreign policy and diplomacy.
The notion that the CFSP is not a homogeneous policy, often resulting from the lowest common denominator between MS's foreign policies and interests, is particularly relevant as this can be extremely difficult to achieve. Since diplomacy requires a careful and thorough approach, and aspirations of individuals that participate in these processes can impact the outcome of diplomatic negotiations, studying the leadership of a low-profile individual (Ashton) on a high-profile post (HR/VP) acting on behalf of a collective actor (the EU) is particularly relevant for the establishment or reinforcement of the actorness and leadership of the collective actor itself. This is especially pertinent at a time when the EU's normative influence (and ambition, to a degree) appears to be waning, as the 2016 EU Global Strategy seems to imply. Through this case we can better appreciate the extent to which early incursions on behalf of the EU's HR/VP ended up enabling or constraining the EU's actorness, and the continuity and changes in the latter's behaviour as a selfproclaimed normative power.
We found Wurzel et al.'s (2011) leadership conceptualisation particularly useful for our article. This conceptualisation was initially applied by the authors to the EU's role as a leader in the policy field of climate change at the international level. In it, the authors propose a distinction between four types of leadership: structural, which 'relates to the actor's hard power and depends on its material resources'; entrepreneurial, which 'relates to diplomatic, negotiating and bargaining skills in facilitating agreements'; cognitive, which 'relates to the definition and/ or redefinition of interests through ideas'; and symbolic, which 'involves the posturing by political actors which is not followed up with substantive policy measures action and/or the lack of implementation of the adopted policy measures' (Wurzel et al., 2011, p. 13). Wurzel et al., also identify four styles of leadership, establishing opposing dichotomies between themon the one hand heroic, which 'relies on longterm objectives, strong policy coordination and the ambitious assertion of political will' versus humdrum leadership, which 'is incremental, short-term and without the assertion of the ambitious assertion of political will'; and, on the other hand, transformational, which 'leads to history changing events' versus transactional leadership, which 'leads to incremental policy change' (Wurzel et al., 2011). We do not necessarily interpret the latter pair of leadership styles as a blatant opposition and assume there may be a combination thereof, which will become apparent throughout the article. In fact, according to Wurzel et al., 'political success often requires the employment of more than one type (and style) of leadership' (Wurzel et al., 2011).
We define hybrid leadership as entrepreneurial in its reliance on diplomatic, negotiating, and bargaining skills in facilitating agreements (Young, 1991;Wurzel et al., 2011), combined with both transactional (i.e., leading to incremental policy change) and/or transformational aspects (i.e., potentially leading to history changing events) (Wurzel et al., 2011), that is also dynamic and highly adaptive. The hybrid nature refers to the representation and leadership on behalf of collective actorsparticularly in posts like the HR/VP. There are at least two different kinds of leaders in terms of whom they representthemselves or a collectiveand the collective actors can be more or less complex in terms of the multiplicity of levels of representation, accountability, and capabilities at their disposal (Bretherton and Vogler, 2006). Putative leaders, that represent or act on behalf of a collective like the EU, often act with heavy constraints in terms of legal and mandate limits and are answerable to the expectations of multiple independent actors and layers of accountability within that collective actor. Other constraints include Ashton's placement in a relatively salient position in the EU Foreign Policy while being a low-profile figure lacking in diplomatic experience and expertise or being subjected to simultaneously balancing the EU's multilateralism with its principled pragmatism and balancing the EU's teasing of the prospect of enlargement without being able to provide assurances. Thus, the hybrid nature also resides in the leader's behaviour (Young, 1991;Helms, 2014), specifically in their ability to balance all these constraints and levels of accountability and the autonomy to be resourceful and creative in solving problems or in establishing rules and arrangements (Young, 1991) within the range of the positional resources and competences at their disposal (Héritier and Prakash, 2015), and in the ability to capitalise on opportunities (Blondel, 1987;Helms, 2014).
Capitalising on opportunities relates to situational leadership, i.e., a leader's contingency upon the circumstances and context of their action and how these can 'induce cooperation quite apart from the distribution of power or the array of institutions' and how the leader can act upon these opportunities by 'build [ing] or reorient [ing] [the] international political order, rather than the power capacities' of the collective actor being represented (Ikenberry, 1996, p. 395). It also relates to a criterion proposed by Bretherton and Vogler (2006) in their EU actorness conceptualisation. The authors describe 'opportunity' as the 'structural context of action' where actorness (and leadership) may occur (Bretherton and Vogler, 2006, p. 23). This encompasses dynamic processes of shared understandings and meaning attribution constituting intersubjective structures and interpreting material conditions (Bretherton and Vogler, 2006). Thus, the EU's discourses of construction and projection of a particular identity -such as 'soft' power or mediatorand the recognition of the latter's validity by the EU's interlocutors are especially relevant for enabling a leadership role for the EU as a collective actor and for the individuals who speak and act on its behalf. These opportunities materialise when what is expected from the collective actor represented by the leader (e.g., the EU or the EEAS) and what is desirable or expected by the collective actor's interlocutors converge.
Because hybrid leadership is aimed at leaders that represent collective actors, it can also be marked by discursive and power struggles. EU discourses and diplomatic efforts are inherently 'fluid' (Niţoiu, 2013, p. 240), stemming from complex bargaining processes at the national and European levels that take into consideration different governmental and non-governmental interests and actors, popular support, and other national and European level dynamics. Constructivistoriented actorness research proposes that the construction of a EU identity as a global actor and projection and justification thereof onto the rest of the world is mostly developed through practices of 'purposeful construction' (Risse, 2004, p. 154;Bretherton and Vogler, 2006, p. 37). These are carried out by EU institutions and bodies in charge of the EU external action and by the representatives of these bodies and EU MS, which ultimately form discourses disseminated in the name of the EU, which, as they overlap, are institutionalised into narratives (Niţoiu, 2013, p. 240). Such discourses and narratives are formed by proposing or endorsing collective statements that conceptualise and reiterate the EU's identity and the standards and principles upon which it is based, or establish the latter's limits (Diez, 2014). These discursive and power struggles result in constraints that need to be balanced with resourcefulness, creativity and capitalisation on different kinds of opportunities in order for hybrid leadership to transpire.
Hybrid leadership is a constructivist theoretical conceptualisation focusing on the complexity of the (collective) representative role occupied by the putative leader, on the adaptability and dynamism required in conducting their diplomatic and bargaining efforts as well as in balancing the constraints and opportunities offered by the position they occupy, and by the context in which they conduct their diplomatic efforts in the process of guiding or influencing other actors to pursue mutual goals.

Ashton's hybrid leadership in brokering the Kosovo-Serbia Agreement
The agreement between Serbia and Kosovo represented one of the most substantive steps in the normalisation process in decades. It had double positive results: firstly, completing a more than a decade-old cycle of conflict and political instability between the two political entities and their national/ethnic groups, and establishing a new period for promising peaceful relations and progress; and secondly, it has been considered a great success (Gashi et al., 2017) and has helped to characterise the diplomatic approach of the EEAS team and, in particular, of its first chief, HR/VP Ashton (Helwig and Rüger, 2014).

Contextualising the agreement: challenges and opportunities
The agreement between Serbia and Kosovo represented one of the most substantive steps in the normalisation process in decades. It had double positive results: firstly, completing a more than a decade-old cycle of conflict and political instability between the two political entities and their national/ethnic groups, and establishing a new period for promising peaceful relations and progress; and secondly, it has been considered a great success (Gashi et al., 2017) and has helped to characterise the diplomatic approach of the EEAS team and, in particular, of its first chief, HR/VP Ashton (Helwig and Rüger, 2014).
Previously, negotiations between Pristina and Belgrade had been carried out either unsuccessfullyas when delegations from both sides met at the French castle of Rambouillet to discuss NATO's plan (Dauphinee, 2004), which led to the 1999 NATO-led strikes against Serb forces (Roberts, 1999;Papasotiriou, 2002) or under strong political considerations and dissatisfaction due to misinterpretations of the agreementsuch as during the Vienna negotiations in 2007 (D' Aspremont, 2007;Weller, 2008). Following the United Nations' (UN) Comprehensive Proposal for the Kosovo Status Settlement, drafted in 2007 by its Special Envoy Martti Ahtisaari, which required independence for Kosovo, the Serbs ignored the deadline set by the UN Security Council for the review of this proposal. This Serbian reaction (or rather lack thereof) provided Kosovo with the opportunity to declare its independence and sovereignty on 17 February 2008 (Gashi et al., 2017, p. 536-537). The final advisory opinion of the International Court of Justice (ICJ) from July 2010 was ambiguous on this matter, but widely perceived as positive for Kosovo and negative for Serbia 3 . Following the ICJ's opinion, talks between the two sides were aborted, worsening the situation between the two ethnic groups in Kosovo: the Kosovo Albanians and the Kosovo Serbs.
The situation appeared, simultaneously, as an opportunity for the EEAS to get involved in the Kosovo-Serbia case and to appear as the main mediator for a peaceful resolution, after NATO and the UN had failed to achieve a common solution acceptable for both sides. By appointing HR/VP Ashton as chief negotiator, the EU demonstrated that finding a solution for the issue of Kosovo was of great political relevance (Jureković, 2013). In addition to Ashton's leadership, the timing of the ICJ's 2010 opinion and Serbia and Kosovo's willingness to cooperate to 'mak[e] progress with EU integration' (Szpala, 2016, p. 1;Bieber, 2015, p. 294) drove the success of the mediation process and marked Ashton's leadership style. In addition to the context of opportunity itself (Ikenberry, 1996;Bretherton and Vogler, 2006;Helms, 2014), timing was particularly crucial in determining Ashton's success as a leader (Blondel, 1987). The first step in Ashton's strategy to achieve a successful mediation was to make sure the matter of Kosovo's independence and peaceful relations with Serbia was considered significant enough to be included in the sphere of the EU's political activity. Dealing directly with the Serbian side in early September 2010, the HR/VP proposed to Serbian President Boris Tadić that Serbia should draft, with the EU, a UN resolution requiring the transfer of the Serbian-Kosovo unresolved issues from the UN bodies to the EU's institutions (UN General Assembly, 2010).
Despite Serbia's foreign minister Vuk Jeremić's efforts to undermine Kosovo's international recognition process, President Tadić displayed a more amenable disposition to deal with the issue on the EU's terms. This willingness (albeit reluctant) to side with the EU was driven by the fact that, however vague and problematic the ICJ's advisory opinion might have been, by the time it was made public, Kosovo had already been recognised by close to 70 countries. Moreover, the Serbia-Kosovo dialogue that ensued UN resolution 64/298 'provided another argument for holding off recognition until the outcome of the dialogue became clear' (Bieber, 2015, p. 296), which was perceived favourably by the Serbian government. Although Ashton did not directly offer the possibility of accession to either at this point, 'the EU agreed (…) that success in this field would become a condition for further Serbian EU integration' (Economides andKer-Lindsay, 2015, p. 1036), i.e., without it, Serbia would never become a EU MS. The hybrid nature of Ashton's leadership is visible in the balancing of positional constraints and resourcefulness regarding the implicit offer of the potential future EU membership as an incentive. This idea was later reinforced by Angela Merkel, in her visit to Serbia in 2011. Ultimately, this step meant a formalisation of the EU's position as a key mediator in the negotiation processand a de facto recognition of the EU's actorness (Jupille and Caporaso, 1998) as well as of Ashton's role as effectively leading this diplomatic effort.
Leadership does not equate power, but usually requires the latter, and both are 'relational and context-bound' (Wurzel et al., 2011, p. 13). In this case, the EU's power largely stems from the UN resolution requiring the transfer of the Serbian-Kosovo unresolved issues to EU institutions (UN General Assembly, 2010). The context-bound nature of power and leadership is particularly relevant for our study, as it was the Serbian openness to collaborate -advantageous for the EU's foreign policy ambitions -and Serbia's acknowledgement of the EU as an appropriate mediator that provided the HR/VP with an opportunity to step in and offer a viable alternative to Serbia, and thus, with a chance to seize and project (soft) power.
Ashton took advantage of this opportunity and engaged in an entrepreneurial type of leadership (Wurzel et al., 2011, p. 13), not only due to her role in facilitating the 2013 agreement tout court, but also due to her ability to bargain, through diplomatic channels, for a more favourable role for the EU's normative agenda before the agreement was signed. Ashton's hybrid leadership can be construed as entrepreneurial because she was able to help frameand capitalised onthis actorness opportunity for the EU. However, opportunity alone is not enough to understand how and why Ashton's leadership led to the successful conclusion of the agreement.

Ashton's leadership between transactional and transformational
While the HR/VP's leadership was critical for this agreement (Helwig and Rüger, 2014), the case she had to deal with was challenging and it was surprising that most EU Foreign Ministers did not interfere, which can be interpreted as reluctance in believing she could achieve tangible results. Notwithstanding, Ashton took full advantage of the mandate she was given to try to settle this intractable conflict (Garret, 2013). Regardless of the benefits each side could garner, this mediation could only be regarded as an improvement for Ashton's foreign policy experience record, particularly when considering the acceptance of a mutually beneficial political solution. Ashton played an instrumental role in mediating contributions and negotiations. She assumed a hybrid leadership that was simultaneously 'soft' and strategic, offering her the kind of diplomatic success she was looking for to demonstrate the EEAS' value as a strong and capable diplomatic service, enabling and reinforcing EU actorness and visibility (Duke, 2009;Koeth, 2012;Bieber, 2015, p. 292).
Rather than negotiating through representatives, as it had happened in the past, Ashton's interlocutors were Prime Ministers Thaçi, a former military commander of the Kosovo Liberation Army, and Dačić, a former spokesman of the late Serbian nationalist President Milošević. The fact that her interlocutors represented the highest political level also confers recognition upon Ashton and upon the EU as an actor (Jupille and Caporaso, 1998). Her ability to gather both Prime Ministers at the same table and to get them to agree on common ground is a considerable achievement. So, Ashton's hybrid leadership (and the EU's actorness) in the Kosovo-Serbia agreement mediation can be classified as entrepreneurial in that it 'relates to diplomatic, negotiating and bargaining skills in facilitating agreements' combined with a mix of a transactional and transformational, as her leadership lead to 'incremental policy change' but it also ultimately might have led to 'history changing events' (Wurzel et al., 2011, p. 13).
Among other things, because of this mixture of two distinct leadership styles deemed opposing paradigms by the authors -, Ashton displayed a 'hybrid' leadership style in practice. In fact, the combination of both dimensions of this style are precisely what characterised her particular approach to diplomacy and made it a successful and valuable precedent for the post of HR/VP. Ashton's hybrid leadership is noticeable in her proposal for Serbia to consider the EU as the appropriate facilitator (thus conferring actorness 'recognition' to the latter), as Tadić's acceptance thereof resulted in a first step in a process of incremental change that eventually led to an agreement with the potential to change history, or, at least, discursively branded as such, particularly by Kosovo (Beha, 2015). The history-changing dimension is also present in that 'the process and progress of moving a technical dialogue into a political one between the two prime ministers turned two "enemies" of the past into potential peacebuilders in the Balkans' (Beha, 2015).
Following the adoption of UN resolution 64/298, technical talks with representatives from both sides began in 2010. These were initially led by the EEAS senior diplomat Robert Cooper as a facilitator but were later 'elevated to a high-level dialogue' led by Ashton (Bátora et al., 2017, p. 20). During this period, several important meetings were held and, as a result, numerous agreements were conducted, including on the issues of the freedom of movement of people and goods, civil registries, cadastre, recognition of university diplomas, recognition of custom stamps, integrated border management, and regional representation.
Despite the symbolic importance of these agreements, they lacked proper political interpretation. Although their predominantly technical nature also had political problems difficult to avoid, making them volatile and likely to be abused, the more practical goal of the HR/VP and the EEAS team was to lead both sides into reaching common agreements regarding the positive progress of day-to-day life for Kosovo's two ethnic groups. This technical and gradual logic of approximation mimics the EU's own neofunctional/spillover type of integration, as it 'can be considered as a step toward "incremental recognition" by Serbia of Kosovo's sovereignty' (Beha, 2015, p. 117). Our categorisation of Ashton's leadership as hybrid follows a similar logic in its combination of transactional and eventually transformational traits.
Notwithstanding, keeping the dialogue focused on technical, rather than on political issues, was not bereft of problems. This approach lacked domestic support on both sides, particularly regarding the incorporation of Kosovo Serbswhose representation, alongside the normalisation of relations, was at the heart of the dialogue process -, and regarding the development of a sustainable northern Kosovo (Beha, 2015). Moreover, part of the Kosovo Albanians was against establishing a dialogue process with Serbia in the terms that it was being conducted on, as they had initially demanded specific terms and conditions (Bieber, 2015, p. 307). The situation in Serbia was not much different. Serbians displayed caution while attempting to ensure their own primacy in the negotiation rounds and remained adamant about maintaining their position of not recognising Kosovo as an independent state (Bieber, 2015, p. 290). Nevertheless, the fact that, for the first time, the two opposing sides were able to reach and achieve solutions, albeit under the aegis of technical rather than political agreements, was promising and represented a substantial historical achievement in and of itself and an opportunity to continue negotiations.
The 2012 Serbian Presidential elections were decisive for the subsequent step in the negotiations, since one of Ashton's high-level interlocutors would come out thereof and the decision to start a new round of political negotiations had already been made. The victory of the Serbian nationalist party led the HR/VP to initiate new negotiations, not with envoys, nor representatives, but rather with the two Prime Ministers, reinforcing both the political importance of the second phase of the dialogue process and her leadership status.
In a context marked by lack of trust and transparency, Ashton was forced to negotiate very carefully with each side and mediate possible solutions (Hajdari, 2017, p. 92;Beha, 2015). Yet, one could argue that the lack of transparency was purposefully related to the lack of trust, and possibly to 'a deliberate and strategic choice on the part of the EU to allow both parties to interpret the agreements in a way that would be beneficial for their respective positions' (Bieber, 2015, p. 316). This reflects a calculated effort on behalf of the HR/VP to reinforce the EU's position as a relevant actor during this process, to ensure its pivotal role in following negotiations, and her adaptability in a complex and sensitive setting.
Bringing Prime Ministers Thaçi and Dačić together represented a considerable step for furthering the arbitration. Despite the intrinsic challenges, Ashton was contemplating a possible agreement as the foundation for future stability in the region. In Ashton's words, the purpose of that first meeting was not necessarily to settle differences, but to ascertain 'whether the time was ripe for a sustained dialogue' (Ashton, 2013). The subsequent meeting, at the Presidential level, held on 6 February 2013, with Atifete Jahjaga from Kosovo, and Tomislav Nikolić from Serbia, was no less symbolic and conveyed a message of hope regarding the approximation of both parties' positions about resolving the issues between them (Baliqi, 2013). Significant achievements such as the mere realisation of these meetings pose an analytical challenge for a clear categorisation of Ashton's leadership as either transactional or transformational, as it includes facets of both styles. In fact, Ashton's adaptability and capacity to move between different styles of leadership point to one of the strongest advantages which justify her leadership's hybrid nature.
Maintaining the 'quiet diplomacy' approach and a focus on transactional leadership strategies, Ashton managed to arrange for nine additional meetings. While each of these meetings was differently interpreted in both Kosovo and Serbia, there was growing indication of constructive progress, with a mutually acceptable agreement remaining the ultimate goal. On 19 April 2013, such an agreement was reached, with both sides signing a plan consisting of fifteen main targets and thus significantly reinforcing the hope for a peaceful future for the region and its peoples. The final agreement was the conclusion of a six-month term of direct political talks between the two sides, led by Ashton.
Nationalist demands, a logic of alterity, and confrontations still played a significant role in the positioning and definition of national identities in the region. While Serbians were unyielding regarding the recognition of Kosovo's independence and sovereignty, Kosovo Albanians demanded their own independence and insisted Ahtisaari's plan was the best solution to guarantee the rights of the involved parties. Ashton had to achieve an agreement whose guarantee of sustainability and fair implementation for both sides needed to be demonstrated by the EU, to encourage stabilisation efforts and the 'normalisation' of their relations, and to ensure a peaceful coexistence.
Notwithstanding the conceptual and analytical difficulties that derive from the intricacies of this particular case study, we sustain that Ashton displayed a hybrid leadership style as, among other features, we can discern elements of both transactional and transformational styles of leadership in her actions. Transactional elements include the step-by-step approach through piece-meal improvements while transformational elements include reaching a (putatively) history changing agreement. While this identification may be done more effortlessly regarding the former kind, the acceptance of the proposed plan on behalf of representatives from Serbia and Kosovo is an indisputable substantial improvement of the political situation in the region, which remains relevant for EU security from a strategic point of view (Moustakis, 2004;Jureković, 2013), allowing us to also interpret it as a history-changing event in itself. The agreement between Serbia and Kosovo exemplifies how the EU 'can play an important role at the highest international level using its multilateralist approach' (Viilup, 2015).

Actorness through leverage? The (remote) prospect of EU membership
Alongside conflict mediation, the EU's strategy involved engaging with another foreign policy tool: enlargement/accession. This twofold approach is 'a complementary and, at times, conflicting strategy that the EU has utilized in former Yugoslavia with varying degrees of success since the early 2000s' (Bieber, 2015, p. 293). The prospect of EU membership was strategically used by Ashton as an incentive, albeit quite indirectly and remaining a remote possibility for most of the negotiations. Here, the hybrid character of Ashton's leadership is visible in her behaviour (Young, 1991;Helms, 2014), particularly in their skill in balancing the constraints imposed by the EU and its MS that accession was not to be offered straight away and the autonomy to be resourceful and creative in nonetheless teasing about this remote possibility within the range of her positional resources and competences (Héritier and Prakash, 2015).
The European Council granted Serbia candidate status in 2012 (European Council, 2012) in a move that made considerable difference in the negotiation process. In this sense, the HR/VP raised the prospect of both parties' 'European trajectories' as the basis for a common agreement and as a condition both for the agreement and for their future within the EU. Without the use of extortion, but rather through the use of soft power and an awareness of the EU's magnetism, Ashton, echoing Merkel's words from 2011, still made sure both sides were made aware they could not achieve their goals of becoming EU MS without cooperation in this matter.
Alongside 'opportunity', another aspect of Bretherton and Vogler's (2006) EU actorness conceptualisation can be emphasised, namely 'presence'. According to the authors, presence as an actorness criterion is quite encompassing: including elements of actors' (like Ashton or the UN) identification of the EU in a certain wayin this case as a mediator, but also as an ideal model and the ultimate goal to strive for, by means of hinting at future membership prospects. Presence also includes elements of recognitionthrough endorsement of these portrayals of the EU by Kosovo and Serbia's representatives or by the UN by means of both discourse and action. Presence also includes elements of normative influencewhich, in this case, refer to the EU's ability to leverage its interlocutors by means of institutional actors that demonstrate hybrid leadership capacities, such as Ashton. The EU's presence as an actor results in an 'attraction' (Bretherton and Vogler, 2006, p. 211) leading other actors to seek to either emulate it or invest in the path of membership (Risse, 2004, p. 154), when presented with this (however remote) possibility. The third actorness criteria proposed by Bretherton and Voglercapabilitiesis also vital, in the sense that it comprises the tools and mandates attributed to the HR/VP, which limited her actions but, on the other hand, ensured she had the necessary adaptability and dynamism tools to revive and renew the role of the representation and to conduct effective bargaining and diplomatic efforts. Ashton characterised the EU as able to 'make a big difference' and proposed that while 'hard power invites calculation', soft power 'rewards imagination' (Ashton, 2013). Serbia was presented with the prospect of starting membership talks with the EU and, following the agreement, the Council of the EU opted for initiating accession talks in January 2014. By the end of 2019, over a dozen accession meetings between the Council and Serbian representatives had already taken place (Council of the EU, 2019). Kosovo, on the other hand, was offered to start negotiations on a Stabilisation and Association Agreement with the EU (EU and Kosovo, 2015)often considered a preliminary stage in the accession process.
EU enlargements have shown that accession candidates are willing to adapt and submit to the EU's normative power to become part of the EU. But while accession has shown to be in itself an enticing goal for both Kosovo and Serbia, Ashton's careful use of this foreign policy tool as leverage to reach an agreement adds an important layer to her hybrid leadership and clever use of actorness opportunities for the EU without replacing them. The use of enlargement as a leverage tool adds to existing discussions about leadership and actorness in the EU context, but the cautious way in which it was wielded by the HR/VP reveals a need for a more in depth understanding of her leadership in the case of the Kosovo-Serbia agreement.

Discussions and conclusions: lessons for the post of EU High Representative
The increasing salience of the HR/VP in EU foreign policy and diplomacy in the context of considerable changes and challenges in the last decade led us to consider this interinstitutional figure's leadership potential. In this article, we analysed Ashton's role in a key point of her tenure, the 2013 Kosovo-Serbia agreement, in light of our conceptualisation of hybrid leadership. As the first HR/VP since the Lisbon Treaty and head of the EU's first diplomatic service, Ashton's involvement in the agreement process enables us to better understand the type of leadership exercised by this figure and the extent to which it can shape EU actorness and diplomacy.
From the moment Ashton took on the EU's foreign and security policy portfolio, she was faced with harsh conditions she had to overcome to succeed in her mission: sharp criticism from the media and EU technocrats, normative divergences regarding EU MS' foreign policy ambitions for the EU, and the establishment of a new interinstitutional diplomatic service between the Council and the Commission which sought to ease the tension between these institutions regarding the EU's global actorness. Ashton's successful hybrid leadership challenged dominant reproaches and showed her role in consolidating EU actorness and diplomacy.
We conclude by reinforcing the idea that the agreement represented the beginning of a new period in Kosovo-Serbia relations and between the two parties and the EU. Regardless of inherent difficulties, the implementation of the agreement is likely to be the cornerstone for the stabilisation of the region and for both countries' path to European integration. It is, therefore, not only the potentially history-changing outcome of these negotiations which makes the whole process a success under Ashton's leadership and guidance, but also the incremental and 'soft' way she carried out this task.
Considering that, in the context of process tracing, '[causal] mechanisms are not causes, but are causal processes that are triggered by causes and that link them with outcomes in a productive relationship' (Beach, 2017, p. 2), and while we might argue that Ashton achieved the deal partly because she had something valuable to offer her interlocutorsi.e., a (remote) path to EU membership -, her hybrid leadership (which includes entrepreneurial, situational, transactional, and eventually transformational dimensions) allowed her to navigate the most complicated issues over the status of the breakaway republic. She was able to take advantage of a context of opportunities, possibly prescribed within the political space she was acting and aiming at achieving changes; at the same time, on the EU's presence and on the capabilities attributed to her by the EU MS, she used to lead the process with an appropriate level of adaptability and dynamism that contributed to boosting the EU's actorness (Bretherton and Vogler, 2006).
What set the agreement in motion was indeed the right context, which was itself largely triggered by Ashton's hybrid leadership through fostering and subsequently capitalising on key opportunities, such as Serbia's acknowledgement of the EU as an appropriate mediator, ensuring a sufficient window to allow for a broad recognition of Kosovo, oscillating between technical and political talks at key moments, using the ICJ's 2010 opinion and Serbia and Kosovo's willingness to cooperate in exchange of some kind of progress in EU integration, and using the latter as a 'carrot' at the right time. Ashton managed to prove the EU's 'magnetism' is still relevant despite the recent economic and political crises, that it is still a reference model for third parties for emulation or, potentially, integration and that, to a degree, its ontology and teleology converge as a peace promoting project. These are relevant lessons for current and future HR/VPs.
In reaching an agreement in the hard-tested region of the Western Balkans, Ashton's hybrid leadership can be described as adaptable, high-paced, high-level, technical-driven incremental improvements which led to an achievable compromise. A successful agreement with Serbia and Kosovo was crucial for the EU's foreign policy coherence and image, for the validation of Ashton's leadership and of the potential leadership role of the HR/VP post in the context of EU diplomatic efforts. The fact that, in September 2020, both Serbian President Aleksandar Vučić and Kosovo Prime Minister Avdullah Hoti reaffirmed their commitment to EU accession and to continuing work on the EU-Facilitated Dialogue between Kosovo and Serbia, led by HR/VP Josep Borrell, (a sine qua non for that to happen) signals a continued interest in the topic 4 . On the other hand, the lack of real progress since the 2013 agreement, paired with the absence of substantial reforms on behalf of both parties was detrimental to Ashton's legacy and leadership achievements. A new prospect that might prevent EU (or the HR's) leadership from waning and simultaneously provide new opportunities on which to capitalise and boost its role is brought by the Commission's 2021 Enlargement Package (European Commission, 2021), whose effect remains to be seen.
This article also opens new avenues for research by proposing a new layer in the international leadership debate and presenting the opportunity to develop a comparative analysis of the different styles of leadership exercised by the HR/VPs to better appreciate nuances in this area of the EU's evolving actorness. A comparative study could also help to better understand the different factors that enable or constrain EU actorness as a peace mediator, also reinforcing the debate on this topic, in addition to allowing for a possible generalisation of our theoretical contributions beyond the analysed case study.