As Clouds Gather Over Europe, Leaders Seek Unity in Churchill’s Birthplace

The venue is a glittering 18th-century palace and the birthplace of Winston Churchill. The guests include more than 40 of Europe’s leaders. And, King Charles III will be on hand to host a V.I.P. reception.

Yet despite the serene grandeur of the surroundings at Blenheim Palace, near Oxford, the continent’s top politicians will meet on Thursday in a mood of heightened anxiety and with a growing urgency to find common cause in an unsettled world.

Rolling out the red carpet as host is Britain’s prime minister, Keir Starmer, who is pushing to strengthen British relations with European governments on security, migration and trade, as the world contemplates the prospect of a return to the White House for former President Donald J. Trump.

The meeting is the fourth of the European Political Community, the brainchild of the French president, Emmanuel Macron, in 2022, who wanted countries across the continent to work together to confront collective challenges.

There is no shortage of those today, with war raging in Ukraine and the possibility of a second term for Mr. Trump, who has threatened to undermine NATO by withdrawing protection from countries that fail to pay their way. Some European lawmakers have worried openly that a Trump administration could end support for Ukraine and embolden Russia. In March, President Donald Tusk of Poland warned that Europe was in a “prewar era” and should prepare accordingly.

“Clearly events in Milwaukee will hang over this summit,” said Kim Darroch, a former British national security adviser, referring to this week’s Republican National Convention, where Mr. Trump announced J.D. Vance, a critic of U.S. support for Ukraine, as his vice-presidential nominee.