1) Russia's war in Ukraine

The 27 member states of the European Union have repeatedly promised to help Ukraine for as long as it needs to defend itself against Russia. EU leaders generally agree that a victory by Russia would be dangerous for the European Union's security. But the question now is whether they will continue to stand by Ukraine in 2024.

Recent weeks have seen a lot of discussion of war fatigue and waning solidarity in Brussels. EU member states are finding it difficult to unanimously sign off on the financial aid that the European Union has promised. The current approach, that it's up to Ukraine to decide whether to negotiate with Moscow, may be called into question in the coming year.

"The first objective must be to continue to work for a just and lasting peace, not another frozen conflict," European Commission President Ursula von der Leyen said in November. "The best way to give Ukraine stability and prosperity in the mid- and long term is, of course, membership in the European Union."

2) EU enlargement

Almost all member states have said they want to see Ukraine join the club, but in private leaders concede that von der Leyen might be going too far and too fast. Ukraine and Moldova are set to start official accession negotiations in 2024. But having a war-ravaged Ukraine integrate into the European Union could have enormous costs for the existing member states.

Even Ukraine's closest backers, Poland and the Baltic EU member states, seem to be getting cold feet. They could go from being net receivers to net payers in the bloc's budget. Behind the scenes, EU officials have been trying to calm concerns. They've said negotiations may begin, but accession could be years, or even decades, away.

All six of the western Balkan states still awaiting EU membership would like to follow in the footsteps of regional trailblazer Croatia and join the bloc. Some have been waiting for 20 years and are now watching suspiciously as Ukraine and Moldova have their bids pushed ahead.

Montenegro, Albania and North Macedonia are expected to receive provisional accession dates, in part to mitigate growing Russian and Chinese influence in the Balkans.

For Serbia and Kosovo, accession prospects look less strong, with persistent strife between the two hindering their progress.

Bosnia-Herzegovina is struggling to shake off the status of a dysfunctional state. The biggest obstacle here is conflict between Bosnian Serbs and other ethnic groups, fueled by Russia.

3) The EU's own internal issues

As accessions await, the European Union has internal work to carry out. Changes are needed to decision-making processes and financing.

French President Emmanuel Macron has long argued that only an independent, economically strong European Union can absorb new members. The German government has proposed making decisions by majority, rather than unanimity, a current requirement that has been a frequent cause of holdups at EU summits.

EU diplomats have said it's unclear whether any changes will be implemented in 2024. Abolishing unanimity would require a unanimous decision from all member states. In recent years, however, the European Union has not managed to secure the assent of the two notorious naysayers, Hungary and Poland, who have frequently made use of their veto power.

Punitive steps to address backsliding on the rule of law within member states appear to have had little effect. An increasingly combative Viktor Orban will remain Hungary's prime minister in 2024. In Poland, on the other hand, former European Council President Donald Tusk is taking the helm.

Adopted by member states in 2007, the Lisbon Treaty continues to set the rules for the bloc. In 2024, expect more discussion of whether those rules are still fit for the task.

4) Donald Trump

Depending in part on the outcome of a string of ongoing court cases, the potential return of firebrand Republican Donald Trump to the White House would be a headache for the European Union and for many NATO members. The EU could lose the United States as its closest ally in trade, supporting Ukraine and deterring Russia.

The German American Chamber of Commerce worries that a reelected Trump would impose punitive tariffs on trade with EU members. In return, the European Union would have to increase customs duties and taxes. Trade volumes would likely fall, and economic growth would be curbed.

5) EU elections

In June, voters EU-wide will head to the polls to elect the European Parliament. Last time they had the chance, only about half of eligible voters turned out. The center-right European People's Party is expected to once again come out as the largest group in the parliament. The far right is also expected to do well.

According to a Eurobarometer opinion poll, the biggest issue for voters is their individual economic situation and standard of living. Ukraine, migration and EU enlargement all come much further down the list when it comes to voters making their choice.

Von der Leyen may well stay on for a second term as president of the European Commission. But first, she would need to be nominated by the 27 member state governments and then be confirmed by the European Parliament.

This article was originally written in German.