BRUSSELS — NATO leaders are gathering in London on Tuesday to celebrate the 70th anniversary of the military alliance — and organizers are hoping to avoid any fireworks.

Nervousness is running high about President Trump’s commitment to the alliance, which was founded to defend Europe from the Soviet Union and has evolved to take on security issues beyond the continent.

At previous NATO meetings, Trump declined to affirm the Article 5 principle that an attack on one is an attack on all, and he intimated that he would pull the United States out if Europeans didn’t spend more on their own defense.

This time, organizers are fighting a multi-front battle against slinged arrows from friends, with French President Emmanuel Macron joining the fray with gusto. The French leader has been incensed by the United States’ lack of coordination with its allies, in Syria and elsewhere, and in an interview last month declared NATO had suffered “brain death.”

A NATO diplomat, speaking on the condition of anonymity to sum up dyspepsia inside the group’s glassy Brussels headquarters, said, “There’s a 50-50 chance that this goes south,” with both Trump and Macron taking a dash at the alliance’s fine china.

Every last detail of this anniversary get-together has been choreographed to ensure that Trump’s happiness will be maximized and any opportunities to blow up the program, or the alliance, minimized.

Organizers are trying to keep things tight and bright.

NATO leaders will get a dose of regal hospitality at a Buckingham Palace reception with Queen Elizabeth II on Tuesday evening. A formal NATO sit-down dinner isn’t happening, though.

And then, instead of two days of meetings, as is common for full-fledged summits, there will be a single three-hour session at an 18th-century estate outside London on Wednesday morning.

The agenda has been tailored to Trump’s interests. There’s a largely symbolic concession from Germany to save U.S. cash by spending more to pay to keep NATO’s lights on — which diplomats hope Trump will seize as a victory out of proportion with its size. There’s also a report that looks at China’s role as a challenge for the alliance. And defense spending figures have been calculated to emphasize Trump’s influence in getting allies to share the burden.

Secretary General Jens Stoltenberg said at a Friday news conference that the 28 non-U.S. members of NATO have invested $130 billion in their defense since 2016 — an unusual way of presenting spending increases that started after Russia’s 2014 annexation of Crimea.

NATO diplomats say privately that the 2016 peg is for Trump’s benefit. They acknowledge that Trump’s spend-more-or-else approach has indeed scared up more defense expenditures.

The U.S. administration has been glad to take credit.

“We’ve done amazing work over our time in office to get NATO to step up, those countries to spend more money to secure themselves and to secure the world,” Secretary of State Mike Pompeo told Fox News on Monday. “We’re very proud of what’s been accomplished under the Trump administration at NATO.”

One senior NATO diplomat — who spoke on the condition of anonymity to be frank about challenges ahead of the meeting — described the alliance as suffering from “PTSD,” or post-traumatic stress disorder, with Stoltenberg and others focused narrowly on how every alliance decision might play out inside the Oval Office.

When pressed at Friday’s news conference about targeting the gathering toward Trump, Stoltenberg said the things that make the White House happy are also good for alliance security.

“President Trump is right about the importance of European allies and Canada spending more,” Stoltenberg said. “But European allies and Canada should not invest in defense to please President Trump. They should invest in defense because we are faced with new threats and new challenges.”

NATO policymakers describe a strangely bifurcated moment, where U.S. deployments to Europe are at recent heights, the alliance has moved to close many of the security gaps exposed after the Russian invasion of Ukraine in 2014 and security cooperation is closer than ever.

Politically, though, NATO is in a tight spot, with both Trump and Macron taking aim at some of the alliance’s core values.

Turkish leaders, meanwhile, are trumpeting that they have held up approval of classified military defense plans for Eastern Europe because they want tougher NATO language about U.S.-aligned Kurdish fighting groups in northeast Syria, which Turkey calls terrorists. The impasse puts further strain on the alliance.

“This summit is going to be different in the sense that there are at least two, possibly three disrupters converging on a quiet shire somewhere outside London: President Trump, President Erdogan and President Macron,” said Tomas Valasek, a former Slovakian ambassador to NATO. “At least one European leader seems to have had enough and is no longer in a placating mood.”

Stoltenberg flew to Paris last week to talk to Macron ahead of the meeting. But in a joint news conference, the French president did not appear to have been appeased.

“We needed a wake-up call to continue, and I’m pretty glad about it that this was the case,” Macron said. “We have the responsibility of not simply continuing to talk about financial issues, given what the genuine challenges are today.”

For some diplomats, Macron’s focus on problems at NATO has been just as challenging as Trump’s push on spending. In Eastern Europe, leaders feel that calling into question NATO’s defense commitments could embolden Russia to attack. In Germany, Chancellor Angela Merkel has been forceful in her pushback.

“The preservation of NATO is in our fundamental interest today, even more so than in the Cold War, or at least as strongly as in the Cold War,” Merkel told her parliament on Wednesday.

And Macron’s Thursday comments alongside Stoltenberg further frustrated many at NATO, after he appeared to downplay Russia as a core focus of the alliance and boosted terrorism as the main priority instead.

“I hear some saying that Russia or China is our enemy,” Macron said. “I don’t think so. Our joint enemy, clearly within the alliance, is terrorism that’s struck our countries.”

NATO blames Russia for piling up nuclear weapons at its door, trying to undermine alliance democracies, teaming with its enemies in Syria, conducting a widespread cybersecurity campaign, and sparking a war on European soil in Ukraine. Many policymakers feel it makes sense to keep focused on the Kremlin.

The last time NATO leaders got together, in July 2018, Trump hijacked one of the summit’s closing sessions to demand greater spending commitments on the spot from fellow leaders. Anxious diplomats and ministers rushed in and out of the closed-door session looking exhausted. Some later said they had feared Trump would pull the United States out of NATO if he didn’t get what he wanted, an earthquake for the post-World War II global order.

In preparation for this meeting, foreign and defense ministers signed off on the biggest NATO decisions ahead of time, instead of leaving them for leaders to approve in person. Now, leaders can celebrate the individual moves, but no one can hold the changes hostage.

Additionally, this past weekend, NATO diplomats hammered out a two-page declaration for the leaders to endorse, a small victory in the kabuki of summitry that the diplomats hope will help emphasize alliance unity. As late as Friday, diplomats were unsure whether there would be a declaration at all.

And, as a partial sop to Macron, they will agree to a start a “process for reflection” about NATO’s long-term strategy — looking past NATO’s short-term, Trump-generated challenges.