Trans-Atlantic ties between the U.S. and Europe are deteriorating rapidly, with tensions over the Iran war adding to a growing sense that the world’s most important geopolitical partnership is sliding toward a divorce.
President Trump has expressed “disgust” with European allies for not joining the U.S.-Israeli war against Iran, and has mused with aides and journalists about pulling out of the North Atlantic Treaty Organization, the 77-year-old alliance that won the Cold War and, until recently, underpinned the West.
For their part, European leaders have come out staunchly against a war they weren’t consulted on, and which they see as both illegal and ill-advised. After a year in which Trump placed tariffs on European products, scrapped most U.S. support for Ukraine, repeatedly mocked European leaders and threatened to seize the Danish territory of Greenland, they and their voters are in no mood to help out.
At stake in the growing conflict is the future of NATO, which for decades has kept Europe safe and allowed it to prosper. Until recent weeks, Trump’s main complaint about NATO had been about burden-sharing—that European nations weren’t pulling their weight in the continent’s joint defense.
Now, with European members of NATO sitting out the war, Trump is questioning whether defending Europe serves U.S. interests at all if Europeans don’t help American military interventions in the Middle East or elsewhere.
The implication: The U.S. role in NATO is a favor to Europeans, and it needs a quid pro quo to be worth America’s while.
“We would always have been there for them. They weren’t there for us,” Trump told Britain’s Telegraph newspaper this week. European help with the Strait of Hormuz should have been “automatic,” like the U.S. automatically helped with Ukraine, which “wasn’t our problem,” he said.
Lonely superpower
The White House’s stance is a break with American global strategy since World War II, which has treated Europe’s stability and security as a vital U.S. interest. The long-term commitment to Europe came about after the U.S. repeatedly found it couldn’t ignore or stay out of major conflicts there.
The scale of the U.S. military presence in Europe shrank after the Cold War. But U.S. presidents before Trump still saw Europe’s stability as important and American leadership of NATO as useful to that end.
“While you can make a case that things have changed, the vast majority of American strategists would still say Europe is objectively quite important, because of the concentration of wealth, actual or latent military power, and the historical tendency to end up in big fights internally,” said Michael O’Hanlon, director of foreign-policy research at the Brookings Institution in Washington.
The 27-country European Union is the U.S.’s biggest partner for trade and investment. And two-thirds of Americans say the U.S. benefits from NATO membership.
Trump has never liked the alliance, but this past week marked a shift, said François Heisbourg, special adviser at the Foundation for Strategic Research in Paris and a former French official.
“The Americans are talking directly and openly about doing away with NATO. The notion that actually it’s expendable—that is new,” he said.
Allies need to take the breakup scenario seriously, Polish Foreign Minister Radoslaw Sikorski said on X Thursday. “Of course, we want to be a good, loyal ally of the United States, but we cannot pretend that the U.S. President isn’t saying what he is saying.”
Over the past year, even staunch allies have lost confidence in the U.S.’s judgment and decision-making, following Trump’s bid for Greenland and an approach to the Russia-Ukraine war seen as favoring Moscow.
U.K. Prime Minister Keir Starmer, who has been repeatedly belittled by Trump, said this past week Britain was pivoting toward Europe in both economic and security policy. The implication: It can’t count on the U.S.
As recently as February, when the U.S. pulled out of some NATO command roles, the message was that Washington remained committed to the alliance but Europe should take on more of its work. That stance was seen as reasonable in Europe, said Fabrice Pothier, chief executive of geopolitical consulting firm Rasmussen Global.
On Iran, “Trump is kicking and screaming because he made a unilateral move with only Israel and how he’s realizing it’s pretty heavy lifting,” said Pothier. “The U.S. is going to be a more lonely superpower—at a higher cost to itself.”
Allies with boundaries
The Trump administration’s anger has boiled over in part because European countries including France, the U.K., Italy and especially Spain have put limits on how the U.S. can use their air bases and airspace for the war. European allies have also rejected Trump’s demands to send naval forces to help reopen the Strait of Hormuz while the war is still raging.
Yet Europe has also quietly facilitated the campaign against Tehran. U.S. military aircraft and ships have used bases in the U.K., Germany, France, Italy, Portugal and Greece for logistical support as well as strikes against Iran. Some European countries have also sent air-defense assets to help protect friendly Gulf countries against Tehran’s missile and drone strikes.
European officials say NATO has always been a relationship with boundaries. Its charter defines it as a mutual-defense pact covering Europe and North America. Members aren’t obligated to support U.S. wars of choice in other regions such as the Persian Gulf.
Trump’s insistence that NATO didn’t show up when the U.S. needed it is seen in Europe as deeply unfair. Since its creation in 1949, the only time NATO’s mutual-defense clause has been activated was after Sept. 11, 2001, when allies rallied to America’s side and joined the U.S.-led war in Afghanistan, suffering several thousand casualties fighting the Taliban. Trump belittled allies’ role in January, wrongly saying they had stayed behind the front line.
“The offense taken to those comments in Europe was palpable and deep, in a way that many in the U.S. didn’t register,” said Philippe Dickinson, a former British diplomat and the deputy director of the Transatlantic Security Initiative at the Atlantic Council, a U.S. think tank.
European leaders still hope to assuage Trump by pointing to their rising military spending. Finnish President Alexander Stubb told Trump in a phone call on Wednesday that NATO was changing, with Europe shouldering more responsibility, his office said.
But Trump is now questioning the whole point of NATO if it won’t follow the U.S. into the Iran war. “COWARDS, and we will REMEMBER!” he fumed in a recent social-media post about Europe not sending naval forces to help reopen Hormuz.
In Europe, some see that as a demand to reinvent NATO as an auxiliary force for American expeditionary wars.
“Trump himself sees no value in NATO other than using it instrumentally as a toolbox to support his unilateral adventures,” said Kamil Zwolski, a scholar at the Royal United Services Institute in London.
Withdrawal symptoms
The alliance isn’t history yet. Trump hasn’t made a decision, U.S. officials say. A move to pull out would face pushback in Washington. On Thursday, Sens. Mitch McConnell (R., Ky.) and Chris Coons (D., Del.) said in a rare bipartisan statement that NATO strengthens American security.
Formal withdrawal from the 1949 treaty that created the alliance would be legally fraught. A law passed by Congress in 2023 says “the president shall not suspend, terminate, denounce, or withdraw the United States” from the NATO treaty unless the Senate agrees by a two-thirds majority or Congress passes a new act.
That provision—co-sponsored by then-Sen. Marco Rubio, who is now Trump’s secretary of state—was adopted after Justice Department lawyers during Trump’s first term asserted that the president has exclusive power to pull out of treaties.
But NATO could fall apart de facto, even if its founding treaty were upheld legally. The alliance’s lifeblood is its deterrent credibility: the perception by potential adversaries such as Russia that attacking a NATO country would trigger war with the full alliance, including the U.S. Trump could also hollow out NATO’s capabilities by slashing the U.S. military presence in Europe.
The American security guarantee for allies “is fundamentally a political commitment, not a legal one,” said Pothier.
Trump still has reasons to hold back from ending NATO, said Phillips O’Brien, a military historian at St. Andrews University in Scotland: Congress would balk, the U.S. still wants to sell weapons to European allies and pulling out would reduce U.S. leverage in world affairs.
For Europe, too, ending the alliance would be costly. Most countries in the region are rebuilding their militaries after years of neglect, but would still need many years and tough spending decisions before they could defend themselves without the U.S.
Optimistic officials in Europe say Trump’s threats are a negotiating tactic to pressure allies into helping more with Iran.
But the question is whether NATO is still an effective deterrent.
“There is no trust left,” said Heisbourg. “It’s like with a divorce: When certain words are used, you can’t walk them back.”
Write to Marcus Walker at Marcus.Walker@wsj.com and David Luhnow at david.luhnow@wsj.com