Recent years have witnessed a resurgence of explicit interstate military conflicts, as geopolitical tensions increasingly develop into confrontations. The Russia–Ukraine war is the defining conflict of this period and forms the basis of this paper. Many actors seek to mediate this conflict while simultaneously supporting Ukraine. Alongside the U.S., the European Union represents the most prominent potential mediator. This article examines whether it can fulfil this role and under what conditions.
Structural Drivers of Mediation and the Acceptance Framework
Modern conflicts are frequently difficult to resolve because they are characterised by profound distrust, information asymmetries (Fearon 1995), and the absence of a clearly defeated side. Belligerents tend to exaggerate their military resilience and understate their vulnerabilities, while political leaders evaluate the state’s interests alongside their own political and personal risks. Mediators can bring the parties’ information positions closer together, provide necessary guarantees for both states and individual leaders, and offer neutral oversight of the implementation of subsequent agreements (Bercovitch and Gartner, 2008). Mediator viability rests on two interconnected pillars: the acceptance by all three parties — the two belligerents and the mediator itself — of the mediator’s role, and a reasonably predictable prospect of success. Acceptance is the only formally mandatory factor, although in practice, a realistic chance of success is required to avoid rejection.
According to Bercovitch and Gartner (2008), mediation is accepted when expected benefits exceed negotiation costs. They explain this through three pillars: “The expected agreement offered by the mediator, the cost of mediation, and the mediator’s credibility.” The expected agreement offers potential benefits to all parties, while the costs reflect the political and strategic risks of mediation. Mediator credibility refers to both its reputation and its ability to influence the implementation of a potential agreement. Therefore, credibility serves as a modifier of expected outcomes: a more credible mediator is better able to convince parties that the promised benefits are achievable. For analytical purposes, the likelihood of acceptance can therefore be represented by a simplified equation, which should be seen as a simplified analytical tool for comparing the relative likelihood of mediation acceptance across the parties:
Likelihood = Credibility × (Benefits − Costs)
While precise numerical values are impractical, qualitative evaluation (None, Low, Medium, High, Very High) offers a structured comparison. Acceptance differs for each of the three parties and should be evaluated separately, as rejection by any single actor would collapse the mediation process. After years of appeals to invite it into the negotiating process, the EU’s willingness to mediate in the Ukrainian war is taken as an axiom in this article. The proposed framework estimates the likelihood that the EU will be accepted as a mediator by both belligerent parties.
Historical Evolution of European Union Mediation Practice
The EU’s history of mediation directly informs its present capacity. The Maastricht Treaty (1992) established the European Union and introduced the Common Foreign and Security Policy (CFSP), the institutional foundation for the EU’s diplomatic practice. The Balkan crisis became the EU’s first major test as a mediator, with peace plans rejected and the Dayton Agreement brokered under American leadership. Nevertheless, the EU rebuilt its reputation through successful mediation in North Macedonia, the Serbia–Kosovo Dialogue, and the Iran Nuclear negotiations, entering a “golden age” until the mid-2010s. Especially important to this article is the 2008 Russia–Georgia War, during which Russia accepted the EU’s mediation efforts. This case demonstrates that, under certain geopolitical conditions, the EU was previously able to act as an accepted mediator in a conflict involving Russia. After 2014, however, the dynamics changed significantly. The EU supported Ukraine and imposed sanctions on Russia, which affected perceptions of its neutrality in some conflicts. At the same time, broader changes in the geopolitical environment, the deterioration of EU–Russia relations, and the preferences of the conflict parties also reshaped the EU’s role as a mediator. Although the EU remained involved in initiatives such as the Iranian Nuclear Deal, its influence in global mediation became more limited. The Armenia–Azerbaijan conflict and the Russia–Ukraine war illustrate that the EU has struggled to act as the primary mediator or exert decisive influence despite its transparent wish. For example, Hall (2025) describes Europe’s role in the Caucasus as follows: “Brussels no longer plays a central role in the talks. The EU signalled willingness to help after the White House ceremony, but no firm commitments have been made.”
Assessing Ukrainian Acceptance of European Union Mediation
Ukraine is the first party to be analyzed because its expected benefits from EU mediation are comparatively straightforward: the end of active hostilities; continued political support and settlement proposals broadly favorable to Kyiv; financial resources for reconstruction and long-term monitoring backed by previous experience in Kosovo and Georgia; the balancing of Russian political influence over the negotiation process; and the ability to both deter renewed Russian aggression and positively incentivize Ukraine through financial assistance and gradual EU integration. Thus, the EU appears to be a particularly favourable mediator for Ukraine. However, all these benefits remain probable. Financing or integration steps may be delayed or even halted by individual Member States; therefore, the expected benefits are assessed as High rather than Very High.
On the other side are costs. The EU may force Ukraine to make some compromises to finally reach the agreement as part of the inevitable mediation process. It can also use the benefits mentioned above as leverage over Ukraine to encourage it to pursue an agreement, thereby reducing Ukraine’s diplomatic freedom of action. In summary, even if the European Union views itself positively toward Ukraine, the possible political risks should not be evaluated at a level lower than Low.
The final factor is EU credibility in Ukraine’s eyes. It seems that Ukraine, both in its political leadership and among the general population, trusts the EU: Chris Powers (2026) argues that “Trust in the EU reached an all-time high, with 82% of respondents saying they tend to trust the bloc.” The EU is seen as capable of fulfilling its potential, especially given its history of participation and success in negotiating other conflicts. Albeit the EU still lacks leverage over Russia despite having previously imposed numerous sanctions. EU credibility can therefore be assessed as High. After putting all results into the aforementioned equation, it yields Lu = Cr(B – C) = High (High – Low), which can be interpreted as a High likelihood of acceptance. The Ukrainian assessment, therefore, suggests that the European Union meets most of the conditions associated with successful mediation.
Assessing Russian Acceptance of European Union Mediation
Analysing Russia requires recognising that the EU is no longer an independent, neutral actor that maintains pretty equal relations with both sides, as is expected of a typical mediator. The EU directly supports Ukraine while imposing sanctions on Russia, and some Member States facilitate targeted operations against Russian naval/maritime assets. Thus, Brussels can be seen as a side in this war, even if there is no direct military confrontation between Russia and the EU yet. Several of the benefits and costs identified for Ukraine can be viewed inversely from the Russian perspective. The EU’s ability to shield Ukraine from excessive Russian pressure and prevent Moscow from imposing a settlement through superior geopolitical leverage constitutes a clear cost for Russia. At the same time, Russia may see a potential benefit in its ability to influence the European Union itself and to weaken the Ukrainian position by exploiting divisions among member states, as illustrated by Hungary under Prime Minister Orbán in recent years. This does not make EU mediation theoretically unacceptable for Russia. History provides several examples of non-neutral mediators, including the United States at Camp David, Russia in the Armenia–Azerbaijan conflict, and Türkiye during the same Russia–Ukraine war. Neutrality is therefore not a prerequisite for mediation but one of the factors influencing a mediator’s credibility.
From the Russian perspective, potential benefits of EU mediation include the end of active hostilities, including Ukrainian strikes on Russian territory and infrastructure, as well as the possibility that Brussels could pressure Kyiv toward compromises necessary for an agreement. Given its political and economic influence over Ukraine, the EU could also help monitor and maintain a future settlement. Additionally, Russia could view sanctions relief and gradual restoration of economic relations as potential incentives, although these depend on European political decisions. Therefore, expected benefits can be assessed as Medium, with the potential to reach High under different political circumstances.
The expected costs, however, are considerably higher. Russia would lose the opportunity to improve its position on the battlefield while facing a mediator perceived as politically closer to Ukraine. Furthermore, the EU’s institutional involvement, following years of support for Kyiv, creates additional political and geopolitical risks for Moscow. The costs can therefore be evaluated as Very High.
The EU’s credibility from the Russian perspective is likewise limited. Europe seems non-neutral (RBC-Ukraine, 2026), has experienced deteriorating relations with Russia since 2014, and institutionally integrates Ukraine into itself, for example, through the official candidate status and EUMAM Ukraine. Overall, this reduces Russia’s expectation that Europe can act as an acceptable mediator. Furthermore, Brussels has limited leverage after imposing extensive sanctions, as described by TASS (2026): “The European Union has exhausted its supply of ideas for new measures that could be included in the 21st package of anti-Russian sanctions, as additional restrictions increasingly conflict with the interests of member states.” This further limits the EU’s ability to force Russian acceptance. Consequently, the EU’s credibility for Russia can be assessed as no higher than Low. Likelihood in the most positive case can be seen as Lr = Low (High – Very High). This shows that the problem is not the absence of benefits for Russia, but rather high costs and low credibility that prevent acceptance. They become the thing preventing Russia from accepting EU mediation and thus halting the whole process. A total comparison of Ukraine and Russia allows us to create a table to visualise the current state of all indicators for both sides:
| Indicator | Ukraine | Russia |
| Expected Benefits (B) | High (Security guarantees, reconstruction, integration) | Medium/High (Ceasefire, potential sanctions relief) |
| Expected Costs (C) | Low (Concession pressure on negotiations) | Very High (Loss of battlefield position, non-neutral mediator) |
| Mediator Credibility (Cr) | High (82% public trust, proven political support) | Low (Active sanctions, military support to Ukraine) |
| Acceptance Likelihood (L) | High | Very Low |
Comparative Assessment of Mediation Acceptance Likelihood
Conclusion: The Geopolitical Capital Trade-off
This article shows that the acceptance of a mediator is less about neutrality or political games within a state than about the accumulation of the needed geopolitical capital. Throughout the 2000s, the European Union accumulated political capital as an accepted mediator. Since 2014, it has increasingly invested this capital into another strategic role — becoming Ukraine’s principal supporter. This choice strengthened European influence over Kyiv while reducing Moscow’s acceptance. The analysis does not judge this strategy normatively but demonstrates its consequences. It is still possible for the EU to exchange some geopolitical capital in Ukraine toward rebuilding relations with Russia to be accepted as a mediator. Thus, the EU has a choice to act – maintain its support for Ukraine and stop trying to accumulate power as a mediator, or play back some relations with Ukraine to rebuild ties with Moscow and accumulate some of the needed capital. Nowadays, the second option seems impossible for the EU, and the author argues that, under current conditions, it is no longer possible for the EU to serve as a mediator because of the high, unpredictable costs for Russia and low credibility in Russia’s eyes. Although the EU is not the only geopolitical actor that can mediate such conflicts, the timely implementation of its role in this conflict and the alignment of its geopolitical direction with the right course will only strengthen the EU. As shown in this article, the analytical approach can be applied to any other state that wants to become a mediator across the past, present, and future.
References
Bercovitch, J. and Gartner, S. S. (2008) International Conflict Mediation. 1st edn. Routledge. Available at: https://www.perlego.com/book/1695392
Fearon, J. D. (1995). Rationalist Explanations for War. International Organization, 49(3), 379–414. http://www.jstor.org/stable/2706903
Hall, B. (2025, September 5). Azerbaijan, Armenia, and the Trump deal. Carnegie Endowment for International Peace. https://carnegieendowment.org/russia-eurasia/politika/2025/09/azerbaijan-armenia-trump-deal
Powers, C. (2026, June 26). Ukrainians’ trust in EU reaches record high, corruption seen as top obstacle to membership, survey finds. The Kyiv Independent. https://kyivindependent.com/ukrainians-trust-in-eu-reaches-record-high-survey-finds/
RBC-Ukraine. (2026, June 18). Putin rejects Europe as mediator in talks with Ukraine. RBC-Ukraine. https://newsukraine.rbc.ua/news/putin-rejects-europe-as-mediator-in-talks-1780632625.html
TASS. (2026, July 18). Russia says European Union has exhausted most sanctions leverage against Moscow. https://tass.com/world/2163515
Treaty on European Union (Maastricht Treaty). (1992, February 7). Official Journal of the European Communities, https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A11992M%2FTXT
