1. Copenhagen Criteria and Accession Process

Countries must meet the Copenhagen criteria to join the EU. These criteria were established in 1993 and list stable democratic institutions, the rule of law, the protection of minority rights, a functioning market economy, and the administrative capacity to implement the Union’s Acquis Communautaire as conditions for membership. After applying, a country may receive candidate status. Formal negotiations begin only after unanimous approval by all EU members in the European Council. The accession negotiations then are structured into six clusters. They cover areas such as the internal market, competitiveness, environmental and digital policies, rule of law, and external relations. Each cluster is opened and closed based on proven progress against clear reform benchmarks. Once all clusters are closed, an accession treaty is signed and ratified by the EU Parliament, all member states, and the candidate country itself. The negotiation process is a huge legislative and technical challenge. While Austria’s and Sweden’s accession took a couple of years in the 1990s, further EU enlargements took more than a decade: the so-called Luxembourg Group that encompassed ten states in Central and Eastern Europe, the Baltics, and along the Mediterranean Sea started negotiations in 1997 and joined in 2004. Romania and Bulgaria joined in 2007 after negotiations started in 1999. The Union’s youngest member state, Croatia, joined in 2013 after eight years of negotiations.

2. Current EU Candidate Countries

At present, nine countries are officially candidate countries: Albania, Bosnia and Herzegovina, Georgia, Moldova, Montenegro, North Macedonia, Serbia, Türkiye, and Ukraine. In December 2022, the government in Pristina also formally applied. But due to the ongoing recognition debate on Kosovo amongst EU member states, it can not be considered as formal candidate country. At the Thessaloniki Summit in 2003, the EU affirmed that the Western Balkans had a future within the Union. Alongside the promise of eventual membership, the region was expected to foster good neighbourly relations and strengthen regional cooperation, while also benefiting from EU incentives such as dedicated financial instruments. In the years that followed, the enlargement process advanced unevenly across the Western Balkans and later extended to the wider Black Sea region, where Russia’s full-scale invasion of Ukraine injected new urgency into the EU’s enlargement agenda. Türkiye, by contrast, has remained a special case: its accession negotiations have been effectively frozen since 2016, in the wake of the political crackdown following the failed coup attempt and the EU’s continued criticism of those measures. Albania and North Macedonia opened accession negotiations in 2022. Montenegro and Serbia began the negotiations in 2012 and 2014 respectively and were once labelled as frontrunners before lack of reform progress and eventual lack of political will slowed down the accession process. Bosnia and Herzegovina received candidate status in 2022. But formal negotiations have not been opened yet. Turning to the wider Black Sea region, Ukraine and Moldova became candidates in 2022 following Russia’s full-scale invasion. Georgia received candidate status in late 2023 after meeting additional reform conditions.

3. Developments in the Western Balkans

In a nutshell, progress in the Western Balkans has been slow and uneven. The Union’s progress reports constantly call for implementation of legislative and technical reforms as well as political reforms. North Macedonia became a candidate in 2005 (then still officially called The Former Yugoslav Republic of Macedonia). Skopje’s accession aspirations were subsequently blocked for years due to the name dispute with Greece and later by Bulgaria on constitutional questions related to ethnic Bulgarians living in North Macedonia. Negotiations were finally launched in 2022 alongside Albania, the accession of which had been originally tied to North Macedonia’s progress, despite having received candidate status already eight years earlier in 2014. Since fall 2024, Albania negotiates the clusters independently from Norh Macedonia. Montenegro’s and Serbia’s negotiations are at times labelled as having lost momentum. Montenegro’s domestic political landscape was often regarded as instable, and dubious Chinese inclusion into infrastructure projects did not contribute to Brussels-Podgorica trust-building.

Serbia seemed to be reluctant to align with EU foreign policy. Brussels was often uneasy with the Serbian stand towards sanctions on Russia and the inability to find an arrangement on the Kosovo issue. Regarding the latter, many outside observers would argue that Belgrade and Pristina share this blame equally. Bosnia and Herzegovina is still plagued by the armed Yugoslav break-up process that resulted in its specific case in the Dayton Accords in late 1995. The Accords provided the country with an overcomplicated constitution allowing irresponsible elites of all constitutionally recognized peoples to block serious reform processes. And although it was granted candidate status in 2022, deep internal divisions and Serbia’s irritating influence on Bosnia and Herzegovina’s entity Republika Srpska have frustrated launching formal negotiations.

Overall, the Western Balkans candidate countries face persistent challenges regarding the rule of law and the fight against corruption. Some, such as Albania and Montenegro, have for example made notable progress in recent years, yet structural weaknesses in judicial independence, transparency, and accountability continue to hamper reforms across the region. Nevertheless, then-European Council President Charles Michel emphasized in 2024 that “because of the war launched by Russia against Ukraine, there is a new impetus, a reinvigoration of the enlargement strategy,” warning that not embracing enlargement would be “a terrible, irresponsible mistake.” His words underline the central tension of the EU’s enlargement debate: geopolitical urgency has increased pressure to accelerate enlargement, yet the Union still insists on a merit-based process built on reforms and benchmarks. This balance between strategic imperatives and procedural conditionality remains unresolved. As a result, the EU granted Bosnia and Herzegovina’s candidate status and stepped-up political and financial engagement across the region. Amongst other instruments, the newly introduced Growth Plan for the Western Balkans (2024–2027), backed by €6 billion, aims to support reforms and facilitate early integration into parts of the EU single market.

4. Developments in the Black Sea Region

As Charles Michel mentioned, February 2022 marked a watershed moment for the EU’s relationship with its eastern neighbours. Ukraine submitted its membership application just days after the Russian attack, followed by Moldova and Georgia. In June 2022, the European Council granted candidate status to both Ukraine and Moldova. It recognized Kyiv’s defense of European values and acknowledged Chisinau’s fragile geopolitical position, as well as its eagerness to tackle long-awaited reforms related to issues such as the Rule of Law, fighting oligarchization, and energy supply.

Georgia’s application was initially met with hesitation. Unlike the previous decade, the country is currently not led by a government enthusiastic to join Western alliances. But despite concerns about democratic backsliding, the EU granted Georgia candidate status in December 2023. However, accession negotiations were explicitly not opened. Regardless of the armed conflict, Ukraine has pushed domestic reforms in areas such as anti-corruption and judicial independence. The European Commission acknowledged Ukraine’s progress in its 2023 enlargement report and recommended the opening of accession negotiations, which were formally launched in June 2024. Ukraine and Moldova are currently in the screening phase of the negotiation process.

In sum, an interim finding for these Black Sea states may suggest that Russia’s full-scale invasion of Ukraine has not merely boosted but fundamentally reshaped the EU’s enlargement approach. What only months earlier seemed politically unthinkable has become a geopolitical necessity. Enlargement is now part of a broader continuum that includes debates on ending the war in Ukraine, security guarantees, NATO perspectives, and intensified European engagement through coalitions of the willing or CSDP instruments. In this strategic context, anchoring Ukraine, Moldova, and Georgia within the Union is seen as vital for European stability and security. Ukraine in particular is already treated in several domains almost like a de facto EU member state. Nevertheless, legislative and technocratic concerns remain, as the EU continues to rely on its merit-based accession framework of clusters, chapters, benchmarks, and conditional reforms. Charles Michel has called on the EU and candidate countries to be “ready for enlargement by 2030” – a timeline that reflects both the urgency felt in Brussels and the complexity of the path ahead.

5. Institutional Implications of Enlargement

Assuming that the candidate countries would somehow be able to meet the Copenhagen criteria, what are the implications for the Union and especially for the functioning of its institutions? The current institutional framework was designed for a smaller Union. It can hardly handle the present number of member states. An enlarged EU comprised of more than 30 members might endanger efficient decision-making and democratic representation and may cause institutional imbalances. If candidate countries do join, reforms will be necessary to keep the Union functional. In light of decision-making processes and voting procedures, unanimous decisions, especially in sensitive areas such as foreign or security policy, might become impossible. Expanding qualified majority voting (QMV) is increasingly regarded as necessary. Even within QMV, rules may need to change. The current threshold for a blocking minority (35 percent of the EU population across at least four states) could provide small countries disproportionate influence. Without institutional adjustments, an enlarged Union risks sliding into policy deadlock or obstruction – dynamics that are already visible in today’s EU, most notably through vetoing or threatening to veto decisions in the European Council by Hungary and, more recently, Slovakia.

Considering the European Commission’s size and efficiency, the current structure might not survive. If each member state insists on a Commissioner position, the Commission could grow to 35 members. A Commission of that size is widely seen as hampering efficient governance. Reform ideas include reducing the number of full Commissioners, introducing deputies instead, and establishing a clear hierarchy by introducing Lead Commissioners and corresponding Commissioners.

In addition, representation in the European Parliament would need to be reviewed. New members will send MEPs to Brussels, but the total number of seats is currently capped. Increasing the number of seats and/or supporting a policy that requires present members to give up seats seems to be politically delicate. Ukraine alone could merit 40 to 50 seats. One solution could be to expand the total number of MEPs and accordingly amend the Lisbon Treaty. In any case, the European Parliament’s internal balance and functionality will need to be recalibrated. In sum, enlargement cannot succeed or be implemented without institutional adaptation. Reforms to voting rules, the Commission’s set-up, and the Parliament’s size must go hand-in-hand with accession. Brussels-based decision-makers increasingly acknowledge internal reform as a prerequisite, more than a simple parallel process, for a credible and effective enlargement. But amending the Lisbon Treaty or even drafting a new Treaty would require political agreement amongst the present member states’ capitals. The outcome of this process is hard to predict.

6. Policy and Fiscal Implications of Enlargement

Setting aside the need to prepare the EU institutionally, there are many more aspects such as policy adjustments, managing phasing- periods or recalibration of the regional funds. In this frame, we wish to consider another aspect of EU enlargement: the financial implications for the Union and its present member states. Integrating beneficiary countries into the EU requires substantial financial resources. This applies to two major budget instruments: the Common Agricultural Policy (CAP) and the Cohesion funds. Both would need to be increased significantly. Most candidate countries have Gross Domestic Product (GDP) levels well below the EU average. For example, in 2023, Ukraine’s GDP per capita was roughly 12 percent of the EU average, and Serbia’s was approximately 30 percent. These disparities mean that under the current rules, new members would be entitled to considerable budgetary support.

An enlarged EU would need to revisit its CAP because many of the candidate countries have large rural sectors and relatively low farm incomes. Ukraine, as a case in point, has a vast agricultural base and hence could become the largest CAP recipient. Bruegel, a European think tank specialising in economics, estimates that CAP expenditures would need to rise by around 25 percent if current policy levels are maintained and if all candidate countries were to join. This could add more than €100 billion over a multiyear budget cycle. Suggestions range from reducing per-hectare payments to introducing caps for large agribusinesses or reforming the CAP in light of targeting small and sustainable farming.

In light of the EU’s Cohesion Policy, enlargement would also have a significant impact on development funding allocated to member states and their regions. Integrating more economically weaker countries would lower the EU's average GDP per capita and shift the eligibility for funds toward new members. Central and Eastern European countries (for example Poland, Hungary or Romania) could lose part of their current benefits. According to Bruegel, cohesion spending could increase by seven percent in a future multiannual EU budget. If the definition of “less developed regions” changes, some current beneficiaries might lose funding. To soften the impact, the EU would likely use tools such as gradual payment increases and financial safety nets, as it did during earlier enlargements.

One scenario suggests that integrating eight new members could raise the EU budget from 1.12 percent to 1.23 percent of the Union’s total GDP. This means that the share of the EU’s collective economic output dedicated to the common budget would slightly increase to cover the costs of enlargement. This would correspond to an annual budget increase of €15–25 billion. While this amount appears to be enormous, it is comparable to other recent EU projects (like the NextGenerationEU fund). Overall, the needed amount can be considered manageable. A roughly ten percent increase in the EU budget could support countries that together represent about a 15 percent increase in the present EU population. With targeted reforms, especially to the CAP and cohesion policy, the EU can finance integration without compromising fiscal stability.

7. Strategic and Security Policy Implications

While the fulfilment of accession criteria by candidates seems to be questionable, and EU-internal reforms are a must, the financial aspects allow for modest optimism. But is there a strategic rationale for the EU, its member states, and the countries with membership aspirations to undertake these time-consuming, complicated, and complex efforts? Many scholars, politicians, and involved experts argue that all efforts would mean an investment in a more secure and stronger Europe. They emphasize that an enlargement of the EU to the Western Balkans and the Black Sea region would carry significant strategic weight in the context of renewed great-power rivalry and a fading rules-based international order. Some voices refer to historic lessons and believe that enlargement promotes long-term peace by embedding fragile territories in a stable political and legal order. For the Western Balkans, EU membership is seen as the ultimate guarantee against renewed ethnic conflict and state fragmentation. It ties former adversaries into a shared institutional framework, as it did for France and Germany after 1945. In this light, the accession process also encourages conflict resolution, such as putting pressure on Serbia and Kosovo to normalize relations and incentivizing cooperation among Bosnia and Hercegovina’s political factions. Related to Ukraine, Moldova, and Georgia, EU integration could mean a final exit from a Moscow-dominated post-Soviet space. Especially for Ukraine, candidate status was interpreted to have supported public resilience and hope for the post-war period.

Observers also argue EU accession would reinforce democratic norms and ensure rule of law, establishing a strategic counterweight to authoritarian influence from external actors. Moscow and Beijing are perceived as leveraging energy resources access, aggressively promoting alternative societal models and power politics successes. In contrast, the EU offers rules-based governance, open market access, and democratic and trade standards. Enlargement would thus become a tool of geopolitical competition demonstrating that the European model remains viable and attractive. Notwithstanding failures concerning EU member states’ democratic backsliding, the argument is that candidates would have to fully align with EU foreign policy once they joined the Union. Thus, opportunities for external regimes to exploit internal divisions would be reduced.

The security and defense community argument emphasizes that a bigger EU would strengthen collective security. Being mindful that the EU does not per se constitute a military alliance, enlargement would have indirect, but powerful security benefits. The political message underlines deterrence: extending the EU umbrella to Ukraine or the Western Balkans signals that these countries are firmly anchored in a Collective (European) West. While Article 42(7) TEU establishes a mutual assistance obligation, it has only been invoked once so far, by France in 2015 after the Paris terrorist attacks, and has largely remained a political deterrence tool in practice. Especially regarding Ukraine, enlargement advocates refer to the multilayered aspects of security. The country would benefit economically through access to the single market, development-wise through the above-mentioned funds, energy-wise through integration into EU grids, and of course politically through formal alignment with Western Europe. In this view, the security and defense community strongly underlines that Ukraine would not only join to benefit. It would also bring something to the table. Kyiv has the strongest conventional armed forces in Europe, and its forces have battlefield experience. Moreover, its society and defense sector offer most valuable defense capability innovations, resilience expertise, and general insights into current strategies and tactics necessary to counter the Russian way of warfare. Hence, in terms of applied crisis response, Kyiv might appear as donor and Union member state as beneficiaries.

Grand strategists point out that a larger EU with over 500 million citizens and of strategic geographical significance would be a more influential global actor. For example, Ukraine’s agricultural exports and the Black Sea’s connectivity might enhance the EU’s relevance in food security, transportation policy and global commerce. New members would also increase the EU’s voting weight in international organizations. More importantly, enlargement shows that the Union can adapt and grow even under geopolitical pressure. This would send a global message that democracy and integration are prevailing over aggression and fragmentation. Moldova and Georgia could benefit similarly, gaining long-term protection from destabilization. From the EU’s perspective, this enlargement closes a major security gap along its Eastern flank. Membership would replace a buffer zone of vulnerable states with a belt of democracies integrated into European structures.

Enlargement enthusiasts argue that EU accession should not be dominated by bureaucratic formalities but needs to be seen as a strategic process that demands clear political direction. According to this camp, enlargement is more than a mere checklist of technical conditions. It means engagement in dispute-settlement, active reform support and providing stability (for example through Common Security and Defence Policy missions). Enlargement supporters believe that the Union needs a strategic response to instability in its neighbourhood. EU enlargement backs peace, counters rival powers, strengthens democratic governance, and encourages the EU to act more decisively in a contested global environment. Any other option would result in much higher costs.

Enlargement sceptics allude to the dire record of reform progress in candidate countries. They emphasize that the legislative, technical, and bureaucratic benchmarks of the Copenhagen criteria represent European values. Thus, nonfulfillment means that a country doesn’t share the same values with the Union and its member states. In addition, sceptics underline the difficult process required to reshape EU institutions to accommodate additional members. Finally, some of these voices warn that there might be little appetite among current beneficiary member states to accept reduced financial support from Brussels, given the additional CAP and cohesion funding that would be needed for new members.

8. Outlook

This contribution does not want to weigh which view shall prevail. Both, the strategic approach to stress the geopolitical necessity and the rather technocratic angle to insist on merits-based membership have pros and cons. Ultimately, it cannot even be predicted if the current pool of potential candidate countries will remain. Taking current geostrategic factors into consideration, including great power competition, societal polarization, competing narratives, trade uncertainties, burden-shifting in existing alliances, and possible expansion of armed conflict in Europe, elites and electorates in candidate countries might disengage from further European integration. Georgia already opted out of the negotiation process. And challenged by a wider variety of Moscow-generated hybrid means to influence Moldovan society such as massive mis- and disinformation campaigns, elections in Moldova revealed that only out-of-country votes led to a narrow victory by the pro-European camp. In the Western Balkans, it can’t be ignored that a shallow deal to freeze Russia’s war in Ukraine combined with prevailing narratives towards a weak EU could constitute a game changer. It might encourage elites, for instance in Belgrade or Banja Luka, to question the current territorial borders. But an unsatisfactory peace deal could have a counter effect, too: aggressive external actors may also encourage citizens and governments to seek for even faster protection under Brussels’ umbrella.

Ending on a careful note, being “ready for enlargement by 2030” sounds ambitious and perhaps even necessary. It certainly is a message of hope in times of global uncertainties and international distress, but it also opens windows of opportunities. Yet, this message should also take into account that conditions such as internal political and institutional reforms and external commitments need to be met. As Charles Michel stated, “We are on the doorstep of another historic moment for our Union. We have a date with history. Let us take it with both hands.”

Dr Sebastian von Münchow is a Bundeswehr professor and researcher at the George C. Marshall European Center for Security Studies (GCMC) in Garmisch-Partenkirchen. His research areas include the euro-atlantic integration of Eastern Europe, EU-NATO cooperation, International Organisations, and constitutional law and security in the Western Balkans.
Benjamin Spindeldreier holds a B.A. in Political and Social Studies from Julius-Maximilians-Universität Würzburg and completed an internship at GCMC. He is currently enrolled in the Master Programme of International Affairs at Hertie School in Berlin.