Yves Herman / Reuters

BRUSSELS — Is NATO really that afraid of Donald Trump?

Trump’s first foreign trip as president has so far gone smoothly, and even predictably. At a time when his administration is mired in scandals at home, his journey abroad has been mostly incident-free, including meetings with world leaders in Saudi Arabia, Israel, the Palestinian territories, and Rome. But on Thursday, Trump enters a more complicated world of multilateral diplomacy at the NATO leaders’ summit here.

His meetings with various leaders are mostly intended as a kumbaya exercise. But Trump’s wavering stance on NATO — he last called it “obsolete” in January before declaring it “no longer obsolete” in April — has worried allies. So has his long refusal to say he supports Article 5, the provision in the North Atlantic Treaty stipulating that if one of the members comes under attack the others must come to its aid. (The New York Times reported on Wednesday that Trump is expected to finally endorse Article 5 in his remarks in Brussels on Thursday, after having implied that the commitment was conditional on whether allies paid more for their own defense.)

So NATO—the 28-member, 68-year-old military alliance that accounts for billions of dollars in defense spending; the definition of a staid, bureaucratic international institution—joins the list of entities forced to face the conundrum of how to deal with Donald Trump. The Trump-NATO confusion is a sign of how consequential Trump’s open suspicion of existing U.S. alliances and commitments has been on the world stage. The NATO summit this week has reportedly been carefully tailored to him. The agenda is being confined to counterterrorism and burden-sharing — two issues that have been the focal point of Trump’s antipathy toward the alliance. Not on the official agenda: Russia, a NATO spokesperson told BuzzFeed News. Alliance leaders were reportedly told to keep their remarks short during the group dinner to accommodate Trump’s attention span.

“All the Europeans want this to work,” said Thomas Wright, director of the Center on the United States and Europe at the Brookings Institution. “They won’t be able to outdo the Saudis in flattery, but they will try to make him at ease because they need this to work.”

On the burden-sharing front, Trump has repeatedly badgered other members of the alliance to boost defense spending. And he has taken credit for their doing so: “based on our very strong and frank discussions, they are beginning to do just that,” he said in his first speech to a joint session of Congress after being inaugurated. (NATO members pledged in 2014 to increase their defense spending to 2 percent of gross domestic product within the following decade; most members increased their defense spending in 2016, prior to Trump’s inauguration.)

Defense Secretary James Mattis and Vice President Mike Pence have both promised to honor Article 5. On Wednesday, Secretary of State Rex Tillerson told reporters traveling on Air Force One from Rome to Brussels: “Of course we support Article 5. The only time Article 5 has been invoked was in 9/11,” after which NATO joined the American-led war in Afghanistan.

But up until now, Trump himself has not explicitly made that commitment. NATO leadership has finessed the issue; NATO Secretary-General Jens Stoltenberg argued that Trump had essentially endorsed Article 5 in a press conference on Thursday, saying: “By expressing strong support to NATO, to our security guarantees, the United States, President Trump, his security team, has also of course expressed strong support of Article 5, because Article 5, collective defense, is NATO’s core task.” (It was standing next to Stoltenberg, who was visiting the White House in April, that Trump first declared NATO “no longer obsolete.”)

Trump on Thursday will dedicate a 9/11 memorial at the new NATO headquarters being unveiled in time for the summit. It’s there, according to the Times, that Trump will promise to do for the other NATO allies what they did for the United States following that attack. But according to a staffer at NATO headquarters who spoke on condition of anonymity, on Wednesday night working-level staff still didn’t know whether Trump would promise to honor Article 5.

“When you say ‘I support NATO,’ does that mean you unconditionally support defending all the allies?” said Ivo Daalder, former U.S. ambassador to NATO. “Does it mean that you understand that Russia poses the most severe threat to NATO today? On both of those issues Trump has been silent. Strangely silent.”

Russia, of course, is an awkward subject at a moment when Trump’s administration is descending deeper into crisis over an FBI investigation into Russian interference in the 2016 election. The staffer at NATO headquarters said that Russia’s absence from the meeting’s agenda was coincidental.  

“The 25th of May meeting will be short, and focused on two main topics: stepping up NATO’s role in the fight against terrorism, and fairer burden sharing,” NATO spokesperson Oana Lungescu said in a statement. “This is part of NATO’s ongoing adaptation to the most serious security challenges in a generation, including terrorism and instability in our southern neighbourhood, and Russia’s aggressive actions in and around Europe. While we do not expect any new decisions on Russia, NATO allies will reconfirm our long-standing twin-track policy: strong defence combined with meaningful dialogue. As the leaders meet in Brussels, four NATO multinational battlegroups are deploying to the Baltic States and Poland as a clear signal of NATO’s readiness to defend all allies.”

Though Russia’s absence from the list of main topics has raised some eyebrows, others say NATO’S approach this year, with a first-time visit from Trump, makes sense. In any case, leaders can bring up any issue they want to during the meeting, including Russia.   

“I think that the larger goal of having a kind of a calm summit is probably wise done the way it is,” said Toomas Hendrik Ilves, the former president of Estonia. “Burden-sharing and a wider role in counterterrorism is something that he’s stated. This is the first meeting of NATO with a new president. … Nothing glaring has happened on the Russian side apart from just the same old same old.”

NATO may no longer be obsolete, but Trump remains Trump, and he has for years displayed a mistrust of traditional U.S. allies, along with a belief that the U.S. should scale back its commitments around the world. As a candidate and as president, Trump placed an emphasis on unpredictability in foreign relations. “We have to be unpredictable. And we have to be unpredictable starting now,” he said in a speech last year.

“He only said it wasn’t obsolete because it was fighting terrorism,” Wright said. “Not because he believed in its original vision.”

We want to hear what you think. Submit a letter to the editor or write to letters@theatlantic.com.