Silvia Oggiano

EU enlargement is moving further East and South. Source: Osservatorio Balcani Caucaso

The creation of the EU is idealistically rooted in achieving perpetual peace among former arch-enemies in Europe. While the Union has developed into an economic power, political and security concerns were fundamental to its foundation, as the determination to prevent a repeat of the horrors of the two World Wars convinced European leaders to unite. «In order not to allow Europe’s own past to become its future, integration has been made an aim in itself, and an explicit link between security and integration has been constructed».  To enter the Union, two key ingredients are necessary. The first is technical, involving the conditions candidate countries must meet to join, known as the Copenhagen criteria. The second is political, concerning the willingness of EU member states to accept new members, which increases with their perception of security threats. This article will focus on the second one, drawing a parallel between the impact of the war in Kosovo (1998-1999) and the war in Ukraine (2022-ongoing) on EU enlargement.

The impact of the Kosovo War

The war in Kosovo gave new impetus to EU enlargement and the prospect of EU accession became a key objective for Kosovo. Source: Al Jazeera

During the European Council in Copenhagen in 1993, the Copenhagen criteria for membership were defined. Since then, to enter the Union a country must 1) ensure the stability of institutions that guarantee democracy, uphold the rule of law, and protect human rights and minority rights; 2) demonstrate a functioning market economy capable of handling competition and market forces; 3) possess the administrative and institutional capacity to effectively implement the acquis, adopting and enforcing the comprehensive laws and standards required for membership, and showing readiness to fulfill all related obligations. The definition of the Copenhagen criteria was fueled by the trembling security situation at the Union’s external borders, provoked by the end of the Cold War, the dissolution of the Soviet Union, and the ethnic conflicts in Yugoslavia. These geopolitical and security concerns made EU leaders consider the entry of ex-Soviet republics into the Union. During this period, however, EU leaders prioritized ensuring that candidate countries adhered to the required standards for democratic governance, human rights, and economic stability, which are central to the Copenhagen criteria, over the immediate strategic and geopolitical considerations for expanding the Union. That was clearly stated during the 1997 Luxembourg European Council: «the enlargement process should adhere to its iron rule, that is, to start the accession negotiations with candidate countries which fulfilled all the Copenhagen criteria». The NATO operation in Kosovo in 1999 altered this balance, shifting more weight onto the EU’s political will for enlargement. «The EU was mainly driven by the growing sense within the EU that a preventive measure was needed if Europe wished to avoid ethnic conflicts like Kosovo to spread to the rest of the Balkan region». This change in perspective is well illustrated by the British government’s statements, which suggested that when candidate countries face clear threats in their region, the EU should begin negotiations with them to counteract these threats, prioritizing this over full compliance with the Copenhagen criteria. This idea was widely accepted by nearly all member countries during 1999.

To justify its change of approach, the EU described Kosovo as an existential threat to the EU which required emergency measures. «One of the key lessons of the Kosovo crisis is the need to achieve peace and security, democracy and the rule of law, growth and the foundations of prosperity throughout Europe. Enlargement is the best way to do this. There is now a greater awareness of the strategic dimension to enlargement». The Commission proposed abandoning the hard line that negotiations could begin only once all three Copenhagen criteria were fulfilled. Instead, they introduced a new rule to open negotiations with candidates that have established functioning democratic structures, enabling the EU to contribute to peace and security in these countries. What is interesting is that the main beneficiaries of the new sense of urgency brought about by the war in Kosovo were not the countries in the Balkan region but two Eastern European countries that had been left out of accession negotiations due to their poor rate of compliance with the Copenhagen criteria: Romania and Bulgaria. It is true that in May 1999, the Commission proposed new Association Agreements with Bosnia and Herzegovina, Croatia, Serbia Montenegro, Macedonia, and Albania. These agreements aimed to support democracy, the rule of law, economic development, and regional cooperation, offering the prospect of future integration into the European structure. However, at the end of 1999, the EU opened accession negotiations with Romania and Bulgaria, something that would have been impossible before the Kosovo war, and they formally entered the EU in 2007.

The potential impact of the Ukraine war

The impact of the war in Ukraine on EU enlargement could follow the trajectory of the Kosovo War. Source: ISPI

As the war in Kosovo was framed as an existential threat to European security, the war in Ukraine is similarly raising concerns about a direct confrontation with Russia. In her speech presenting the 2023 Enlargement Package, President of the Commission Ursula Von der Leyen said: «Enlargement is an investment in our security. Because integrating new members in the European Union also shields them from foreign interference, and it therefore stabilizes our neighborhood. In times where we see the rules-based international order increasingly called into question, of course a larger and stronger European Union gives us a stronger voice in the world». These words confirm how enlargement is increasingly interpreted as a «political tool at [EU] disposal to respond to security challenges on its periphery». The security threat posed by the Russian invasion of Ukraine is increasing the EU political will to let new member in, providing new momentum for enlargement. As it happened in 1999, less emphasis is placed on the Copenhagen criteria nowadays, and more on the security benefits of enlargement. «The real measure of [the EU] absorption capacity is whether member states can reach any political consensus about when to enlarge and under what conditions. […] These considerations are ultimately far more important than technical or legal ones». However, just as the Kosovo crisis prompted the enlargement toward Romania and Bulgaria, the Ukraine war may finally place the Balkan region as a top item on the union’s agenda. This renewed drive for enlargement is found in the Growth Plan for the Western Balkans, released by the European Commission in November 2023. The plan focused on the technical conditions necessary for EU accession, particularly emphasizing economic criteria. However, these criteria were detailed only following a shift in EU perspective driven by the heightened security threat.


Following the European Parliament elections in June 2024, the next EU leadership faces the task of setting future priorities regarding enlargement. Security and defense were central topics in this year’s EU elections, with EU leaders emphasizing the need to fully support Ukraine against an existential threat that will shape the future of European security. While security and defense dominated public discourse, enlargement did not receive significant attention. Such a pattern was observed since the 1990s, when EU leaders preferred to establish consensus at the institutional level before presenting a unified stance to the public. Today, another reason why politicians tend to avoid discussing enlargement publicly is the concern that this topic may be exploited by far-right parties to attract voters. For instance, farmers have protested not only against environmental policies but also against imports of grain from Ukraine and the country’s potential entry into the EU.


  1. EU institutions should seize the opportunity presented by the war in Ukraine to foster consensus regarding the accession of the most prepared Balkan countries. It is crucial for the EU to remember that stability concerns drove its initial involvement in the Balkans, and that the potential for conflict in the region remains, as recent events in Northern Kosovo have shown.
  2. EU leaders should prioritize the development of a cohesive and ambitious approach to security and enlargement. To achieve this, EU institutions should engage in robust dialogue and diplomacy aimed at building a European strategic culture. Only by addressing these challenges, will the EU be able to act as a geopolitical force.
  3. EU institutions should be reformed to allow for further enlargement, as they lack the necessary decision-making and voting structures to accommodate additional members, particularly a large society like Ukraine. Moving away from the security sector, the funding structure, especially in the Common Agricultural Policy and cohesion policy, requires reform.

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by Silvia Oggiano time to read: 6 min