LONDON — Even before the extraordinary Oval Office bust-up between presidents Donald Trump and Volodymyr Zelenskyy, relations between Washington and Europe were fraying dramatically.

Now — after Friday’s diplomatic implosion between Trump, Zelenskyy and Vice President JD Vance — it’s not clear what the way back could be for the transatlantic alliance built over the past 80 years.

European leaders lined up to support Zelenskyy in an effective rebuke to Trump, who told his Ukrainian counterpart he was being “disrespectful” and “gambling with World War III” by defending his country against Russia’s invasion.

Zelenskyy’s “dignity honors the bravery of the Ukrainian people,” European president Ursula von der Leyen posted on X. “Be strong, be brave, be fearless. You are never alone, dear President Zelenskyy. We will continue working with you for a just and lasting peace.”

Friedrich Merz, the likely next leader of Germany, wrote that “we must never confuse aggressor and victim in this terrible war.” While French President Emmanuel Macron said it was essential to respect the Ukrainians “fighting for their dignity, their independence, for their children and for the security of Europe.”

Perhaps most strikingly, European Union foreign minister Kaja Kallas said that “today it became clear that the free world needs a new leader. It’s up to us, Europeans, to take this challenge.”

Not everyone agreed of course. Hungarian Prime Minister Viktor Orban posted that during the “difficult” Oval Office meeting, Trump “stood bravely for peace.” And other observers faulted Zelenskyy for his part in the exchange, saying he unnecessarily and publicly increased the temperature with a far more senior negotiating partner on which he relies.

But for Zelenskyy’s supporters, these European figures so passionately defend Ukraine because they see it as far more than an internecine conflict raging in the frigid fields of Eastern Europe.

Putin’s invasion is part of a far larger hybrid war, they say, from the Ukrainian battlefield to cyberattacks on Western democracy. They fear that giving the Kremlin a symbolic win in Ukraine may only embolden Russia to expand this assault elsewhere. Doubly so when they accuse Trump of undermining the alliance by barracking its allies and cozying up to Putin, widely reviled in Europe as a war criminal.

This strength of feeling explains why transatlantic relations were splintering before Friday’s undiplomatic scenes. In fact, for the past few weeks, there have been increasing signs that European powers have finally decided to break free from their postwar dependence on the U.S.

“My absolute priority will be to strengthen Europe as quickly as possible so that, step by step, we can really achieve independence from the U.S.,” said Merz after his center-right Christian Democratic Union party won the German election Sunday. He questioned whether NATO’s June summit would still see the alliance “in its current form or whether we will have to establish an independent European defence capability much more quickly.”

It was a jaw-dropping statement from a conservative Americanophile, signalling not just a willingness to spend more on defense, a common Trump demand, but a desire to go it alone.

“I never thought I would have to say such a thing on a television program,” he said.

There are myriad uncertainties about how all this might work. Would Europe’s newfound military independence mean spending parity with the U.S. within NATO? Macron and Starmer, for example, say they have no desire to reduce their cooperation with Washington. Or would American involvement on the continent diminish or even vanish altogether?

Either way, the scale of the challenge is vast. The U.S. military is so deeply ingrained in Europe that its removal would leave “huge holes” in air defense, military satellites and cyberspace, said Sven Biscop, a director at the Egmont Institute, a think tank in Brussels.

Since World War II, the U.S. has agreed to protect Europe’s declining militaries against Russia on the understanding that in return it has been able to spread hard and soft American power through the continent and beyond. Unpicking this symbiosis will take hundreds of billions of dollars, likely footed by European taxpayers already embroiled in a cost-of-living crisis and cuts to public services.

The combined E.U. defense budget of last year, $457 billion, was dwarfed by that of the U.S., $968 billion. Russia’s total, $462 billion, was also larger, despite its far smaller economy, having retooled its entire economy on a war footing since invading Ukraine three years ago.

It will take “5 years as a minimum” for Europe to “fully deter Russia without any U.S. contribution,” said Luigi Scazzieri, assistant director at the Center for European Reform, a London think tank. “You can probably get something that fills a large part of the gap in 2-3 years — but only with a lot of urgency.”

Regardless of those practical mountains, Merz’s comments showed an “understanding that we are in a new era of transatlantic relations,” said Sophia Besch, a senior Europe fellow at the Carnegie Endowment for International Peace, a Washington think tank.

The Trump administration “no longer acknowledges shared community of values, shared interests, and puts forward a very ‘great power competition’ view of the world, where Europe is a side player and Russia is an equal,” Besch said.

The German leader-apparent is far from alone. He has a fellow traveler in Macron, who for years has argued Europe needs to end its reliance on Washington. “We are experiencing a historic moment,” he said Monday in response to Merz’s overtures. “It can lead to an unprecedented Franco-German agreement.”

Biscop believes that these leaders need to form something akin to a European “war cabinet” around which to organize this newfound autonomy. Joining them, he believes, should be British Prime Minister Keir Starmer, Polish Prime Minister Donald Tusk, NATO Secretary General Mark Rutte, and the E.U.’s von der Leyen.

“They need agility and they need to move fast,” he said. “Even faster on Ukraine — because the Americans and Russians are already negotiating.”