Traditionally eurosceptic Denmark votes today in a referendum on whether to overturn its opt-out on the EU's common defence policy.
The vote comes on the heels of neighbouring Finland's and Sweden's historic applications for NATO membership, and as the war in Ukraine forces countries in Europe to rethink their security policies.
More than 65% of Denmark's 4.3 million eligible voters are expected to vote in favour of dropping the exemption, an opinion poll published on Sunday suggested.
However, analysts' predictions have been more cautious, given the low voter turnout expected in a country that has often said "no" to more EU integration, most recently in 2015.
Denmark has been an EU member since 1973, but it put the brakes on transferring more power to Brussels in 1992 when 50.7 per cent of Danes rejected the Maastricht Treaty, the EU's founding treaty. In order to persuade Danes to approve the treaty, Copenhagen negotiated a series of exemptions and it was approved the following year.
Since then, Denmark has remained outside the European single currency, the euro -- which it rejected in a 2000 referendum -- as well as the bloc's common policies on justice and home affairs, and defence.
The defence opt-out means that the Scandinavian country, a founding member of NATO, does not currently participate in EU foreign policy where defence is concerned and does not contribute troops to EU military missions.
Politicians backing the move
Danish voters were given a final chance to hear from political leaders on Tuesday evening, during a televised live debate.
"I vote yes tomorrow from the heart," Danish Prime Minister Mette Frederiksen told the audience. "When there is a war on our continent, then coming together is the best answer we can give."
Mai Villadsen, the leader of the Red/Green alliance, however, disagreed.
"Only today the EU agreed on a new package of sanctions against Russia," Villadsen said. "I think we have shown both in the EU and also in Denmark that we stand by the Ukrainian people. But that has nothing to do with the defence opt-out, it has nothing to do with Russia and Ukraine."
Frederiksen called the referendum just two weeks after Russia's invasion of Ukraine, and after having reached an agreement with a majority of parties in Denmark's parliament, the Folketing. Frederiksen also announced plans to increase Denmark’s defence spending to two per cent of gross domestic product, in line with NATO membership requirements, by 2033.
Eleven of Denmark's 14 political parties have urged voters to say "yes" to dropping the opt-out, representing more than three-quarters of seats in parliament.
Polls opened at 8:00 am CEST and close at 8:00 pm, with the final results due around 11:00pm.