In Brussels, European Union leaders will convene on Monday for informal discussions centered around defense. The meeting takes place while there is still uncertainty regarding U.S. President Donald Trump’s approach to resolving the ongoing conflict in Ukraine, which has been described as Europe’s largest land conflict since World War II and is nearing its third anniversary.

Attending this unique session, dubbed a “retreat,” will be U.K. Prime Minister Keir Starmer and NATO Secretary-General Mark Rutte, joining the EU’s 27 member leaders at Egmont Place. The agenda for the summit will emphasize cooperation between the EU and the U.S., the need for increased military expenditure, and bolstering Europe’s defense sector.

This gathering comes against a backdrop of wavering confidence in Trump, who has previously exhibited a confrontational stance toward allies, including the imposition of tariffs on European steel and aluminum during his first term. His recent remarks have further raised eyebrows, as he expressed the potential for U.S. military involvement in the protection of Greenland and the Panama Canal, stating, “We need Greenland for national security purposes.” Greenland, which has significant U.S. military facilities, operates as an autonomous territory under Danish governance.

In light of this, Danish Prime Minister Mette Frederiksen has been actively working to gain support among European nations, cautioning them about facing a “more uncertain reality.” The defense discussion is anticipated to be a focal point of Monday’s gathering, marking a historic moment as it will be the first EU leaders’ meeting explicitly centered on defense matters, planned to continue for approximately 12 hours.