In 2004, Ireland hosted the Big Bang enlargement when ten mostly central and eastern countries joined the European Union during the Irish presidency.
The Day of Welcomes at Áras an Uachtaráin, replete with fireworks and flag-raising, was rich with the promise of a Europe united, democratic and free, with the Soviet-era division of the continent dissolving to the strains of Ode to Joy.
This week, the European Commission gave its verdict on the next wave of enlargement in a context that could not be more sobering.
Two of those newcomers in 2004 - Hungary and Slovakia - are variously accused of democratic backsliding, frustrating Ukraine's survival and cosying up to Russia.
The European Parliament back then had a total of 67 hard-right or eurosceptic MEPs; today there are 349.
France and Germany, for so long the indispensable double act of European integration, find their politics beset by large far-right and eurosceptic forces, capitalising on anti-immigrant sentiment and a persistent cost-of-living crisis.
That said, Ireland's Government is hopeful that Montenegro will conclude its accession negotiations during the Irish Presidency of the EU next year, a poignant moment whereby the small Adriatic state would restore the Union to 28 following the loss of the United Kingdom through Brexit.
In the interregnum since 2004, there has been a global financial crisis, a migration crisis, a global pandemic, Russia’s invasion of Ukraine and the collapse of the transatlantic relationship under US President Donald Trump.
Even before these omni-crises, it was widely agreed that the 2004 wave would be the last for some time.
Knocking on the door
But time has passed, and nine countries, five of which became candidates before Russia’s invasion, are knocking on the door.
There has been some disquiet that Ukraine and Moldova seemed to be jumping the queue ahead of longstanding applicants; in response, the EU set up a growth plan for Western Balkans countries - North Macedonia, Serbia, Kosovo, Albania, Bosnia & Herzegovina - through increased financial support, while some applicant countries have been integrated into EU defence projects.
The score card this week showed that while Montenegro, Albania, Moldova and Ukraine were in poll position, North Macedonia has stalled in its process due to minority rights and corruption issues, while Serbia's progress appears to have gone into reverse, with problems surrounding the rule of law, freedom of expression, the judiciary and fundamental rights, as well as the problem of Belgrade granting citizenship to Russian nationals, some of whom are deemed a security threat.
Overall, a new accession wave could both strengthen and weaken the EU, a paradox that is prompting whispered concerns in national capitals.
Launching the European Commission’s annual report this week, EU foreign policy chief Kaja Kallas declared: "Through enlargement, Europe can grow its geopolitical power."
Equally, taking on new countries will be both expensive and could frustrate Europe's ability to make decisions, not to mention how to avoid future Hungary's single-handedly vetoing policies which otherwise have unanimous support (Hungary continues to block Ukraine's and Moldova's accession process).
A Eurobarometer survey in September found that 56% of Europeans approve of further enlargement once accession countries meet the necessary conditions, with support particularly high among younger voters.
But there are contrasting views.
While Sweden (79%), Denmark (75%) and Lithuania (74%) are the most enthusiastic, voters in Austria (45%), the Czech Republic (43%) and France (43%) are less so, the latter being a cause for concern given the prospect of a far-right victory in the 2027 presidential election.
The latest European Movement Ireland/Amárach Research poll found that 61% of Irish males and 51% of Irish females support more countries joining.
Accession progress
Undoubtedly, Russia's invasion of Ukraine, and its efforts to destabilise the former Soviet space, have dramatically shifted the imperatives and concentrated minds.
Kyiv applied for membership within four days of the Russian attack and has aspirations to join by 2030 (in the debate over Ukraine’s security guarantees, EU membership has been asserted as the best - if untested - guarantee).
One year ago, and two years into the Ukraine war, a senior EU official said there had been a significant take-up in the reforms needed by applicant countries to align with the EU rulebook.
"Over the past year," said the official, "there has been more progress in accession [negotiations] than there has been in the past five years."
That included the opening of the accession process with Ukraine and Moldova, as well as with Bosnia Herzegovina; Albania, alongside Montenegro, had formulated a target for completing negotiations.
In the second half of last year, Montenegro closed five negotiating "chapters", legislative areas that need to be aligned with EU law. In other words, the small Adriatic country had jumped more hurdles in six months than they had in a decade.

This week, the commission said Albania had implemented "unprecedented" reforms and was on course to complete negotiations by the end of 2027; Ukraine and Moldova both expect to conclude negotiations the following year.
In parallel, the EU has been looking at the institutional, political and financial headaches that a fresh wave of enlargement will undoubtedly bring, particularly around the EU cohesion and agriculture budget, and the decision-making process with up to 35 countries around the table.
Officials point out that the first wave will consist of small countries, which should not mean a huge change in equilibrium.
"Back in the early 2000s when we were looking at the Big Bang accession we had exactly the same discussion," recalls one senior official. "We thought the [European] Union would grind to a halt if its decision making processes weren't reformed. There are clearly challenges and colleagues here experience that on a daily basis. But I would also say that our decision-making processes still work relatively well."
Internal reforms
Some observers believe the EU should complete internal reforms, or even change the Lisbon Treaty, before new accession treaties are concluded with the aspirant member states.
The Brussels-based European Policy Centre (EPC) argues that each round of enlargement has happened against the backdrop of a major historic event: in the 1980s the collapse of military regimes in southern Europe, and the fall of the Berlin Wall and in the 1990s with the Balkan Wars.
The current historical moment of great power bullying and geopolitical upheaval mean Europe must take another stride forward, the EPC says.
"Challenges to the future of liberal democracy in Europe and beyond … [have] all substantially increased the need to widen and deepen European integration," according to an EPC policy paper in April.
What was a Big Bang in 2004 looks now to be a trickle. As such, national capitals want to avoid scary topics like treaty change.
"Everybody's rather happy not to have that debate for as long as we can," says one EU diplomat.
"When Ukraine and Moldova and Georgia became candidate countries there was a sense around the table [among EU leaders] that this could go fast and we should have a discussion about what that would look like. Ukraine is a massive country - how do we keep the EU functioning, if and when we might have 35 odd member states?
"But accession is a long and tedious process, and Ukraine, however well they're doing, isn't going to be joining the EU anytime soon. Does Montenegro joining the EU require treaty change? I don’t think so. It’s a country of 600,000 inhabitants: we'd be back to 28 seats around the European Council table. We've been there before. We didn't need different treaties back then."
Yet, the kind of European Union the new countries are joining is radically different to the collegiate body from the early 2000s. The EU has acquired new competences and responsibilities, mostly willingly granted by member states, thanks to the aforementioned crisis areas: migration, health, defence, climate change.
"EU regulation has become so interwoven with domestic policy making," says the diplomat, "that we want to make sure those joining the club, and who thereby co-decide on the rules that govern our countries, can be trusted, and that they're trusted partners also down the line."
Marta Kos, the EU enlargement commissioner, told the Financial Times this week that Brussels was considering a potential transition or probation period for new entrants.
"I don’t want to go down as the commissioner bringing in the Trojan horses who will be then active in five, 10 or 15 years," she is quoted as saying.
Diplomats point out that even for the ten new members that joined in 2004, entitlements, such as the free movement of workers, access to the Schengen Area and eurozone membership were delayed or staggered (Bulgaria and Romania only became full Schengen members on 1 January).
Currently, all member states enjoy a veto when it comes to common security and defence policy (CSDP), but a number of countries believe that with 35 members, the veto will have to be replaced by a Qualified Majority Vote (QMV).
In May 2023, the so-called Friends of QMV - comprising Belgium, Finland, France, Germany, Italy, Luxembourg, Netherlands, Slovenia and Spain - called for an end to unanimity in foreign and defence policy to allow the EU to take more decisive action against Russia (i.e, getting around Hungary's veto).
"With Russia’s war of aggression against Ukraine there is little appetite for institutional debates on Big Bang changes" says another EU diplomat. "But in principle discussing some sort of safeguards for future accession could make sense."
The special case of Ukraine
Ireland's Government is strictly opposed to dropping the veto when it comes to EU foreign and defence policy for obvious reasons.
However, Minister for European Affairs Thomas Byrne recently told his counterparts at a meeting in Luxembourg that member states would have to spell out what kinds of safeguards or constraints they have in mind once the accession negotiations for Montenegro and Albania are complete, and before accession treaties - formally enacting membership - are drawn up.
"Are some member states going to impose conditions?," he told RTÉ News. "Is it going to mean we need to have a process of reform, or have conditions on new members such as we had before? We need to know now what member states are thinking."
Ukraine is seen as a distinct case. The country is fighting a war for survival, yet is still able to make its way through the accession process. This is partly down to the existential lifeline that EU membership offers, but also to the fact that the disbursements of European loans are tied to reform milestones.
Officials this week said Ukraine's track record has been "overwhelmingly good".
However, there have been setbacks, especially around freedom of the press, and President Volodmyr Zelensky’s attempt - swiftly reversed under local and international pressure - to extend political control over the anti-corruption office.
"The negative trends we've seen, including pressure on the specialised anti-corruption agencies and civil society, really do need to be reversed. That is a slight warning sign," said a senior EU official.
Long term, officials say that Ukraine’s accession will need to be tailor-made, given the size of the population and its agriculture sector.
"It's very clear that simply integrating Ukraine from one day to the next into the EU's agricultural markets doesn't make any sense," one EU source said. "It's not in the interests of Ukraine, it’s not in the interest of the EU and it’s not in the interest of people who consume Ukrainian wheat in Africa."
Optimists point out that in the early 2000s people warned about Poland’s farming sector overwhelming the Common Agriculture Policy (CAP), an outcome that failed to materialise, while the accession of poorer countries like Slovakia added significantly to the EU's value chains, especially in car manufacturing.
But there are plenty of sceptics who believe Ukraine's accession cannot be rushed, or will prove impossible for Europe to digest, and no doubt Russia will inflame those divisions at every opportunity.
For now, the European Commission is attempting to keep the accession process within its procedural guardrails, much to the frustration of those who believe that Europe faces a defining moment
"Wars, populism, migration, technological revolutions and climate shocks are redrawing Europe’s map," says Corina Stratulat, head of European Politics and Institutions Programme at the EPC, "yet the [European] Union and its members still narrate them through templates better suited for regulatory audits than geopolitical transformation."