There’s no telling yet what long-term damage U.S. President Donald Trump and Vice President J.D. Vance’s bullying of Ukrainian President Volodymyr Zelensky may have done to the trans-Atlantic alliance. European allies are putting on a brave face as they stare down the barrel of a full-fledged crisis.

European officials are somewhat resigned to the degradation of the trans-Atlantic alliance under Trump. Some are trying to see the potential upsides, like the end of over-reliance on the United States for security. Yet it’s not just NATO and the previously shared opposition to Russian imperialism that’s in danger, but one of the longest and most successful intelligence-sharing alliances in history.

That intelligence-sharing has historically benefited both the United States and Europe. The United States eyes everywhere, from China to the Middle East. The Europeans, meanwhile, have been able to assist the United States in understanding the motivations of the Kremlin in Eastern Europe. The United Kingdom—through the Five Eyes intelligence alliance that joins it, the United States, Canada, Australia, and New Zealand—has shared its codebreaking and intercepted intelligence since before the end of the Cold War.

Trump is already weaponizing intelligence-sharing, cutting off arrangements with Ukraine in order to put pressure on its government. Western security officials, speaking to Foreign Policy anonymously due to the sensitivity of their positions, fear that the erosion of trans-Atlantic trust might lead to restricted intelligence-sharing between Europe and the United States. They said some countries are already limiting what intelligence they are willing to broadly share with allies and are taking a more bilateral approach to sharing information, on a case-by-case basis.

The immediate concern is that Trump, who has a history of sharing sensitive and classified information, is about to spend time in a room with Russian President Vladimir Putin and other Kremlin officials, with no other allies in the room.

“Of course, you are much less likely to share information when there’s a real risk it ends up with Moscow or MAGA acolytes who cannot be trusted,” a Western intelligence official said.

Trump’s second administration has already raised serious questions for European allies, including those in NATO, about where the president’s international sympathies lie.

“We have to judge Trump on both his actions and his words,” a European security source said. “He wants to kick Canada out of Five Eyes. He’s made Tulsi Gabbard director of national intelligence and Kash Patel director of the FBI. Obviously, that is a big change to the norm and will inevitably make us think twice.”

Trust—and the lack thereof with Trump in office—came up repeatedly.

“The trust within NATO has been built up for decades, since 1949,” a British intelligence source said. “It has been built through facing off mutual threats like the Soviet Union and global terror. But it’s one of those things that’s hard to build up and easy to dismantle.”

Washington and European capitals have disagreed before, of course. The 1956 Suez crisis, where the United States applied pressure on France and the U.K. to withdraw troops from Egypt, is one such example. But intelligence agencies typically understand that while politicians come and go, institutions last decades.

“What might be different about Trump is the apparent support for an actual Russian dictator and the over politicization of government agencies,” the British intelligence source said. “And the fact is we are only just over a month into four years. There’s still a lot of time left for long-standing potential damage to be done.”

NATO officials fear that if this downward trend of trust between allies continues, it will make defending the alliance’s borders operationally much harder.

“It means we get less sensitive and less useful information centrally,” one NATO official said. Trust, of course, is a two-way street. Trump’s rift with Europe has led officials to assume that, in line with the president’s hostility, less U.S. intelligence will now be shared with European allies.

Multiple security officials emphasized that if allies end up in a situation where they are getting less signals intelligence, they lose valuable information on what adversaries might be up to. If they get less surveillance, reconnaissance, and target acquisition, it becomes harder to defend themselves against enemies.

Last week, Defense Secretary Pete Hegseth reportedly ordered a pause on cyber attacks on Russia (the Defense Department later denied this). Many Europeans cited this as the thin end of the wedge. It creates space for Russia and Kremlin proxies to strengthen their grip on the information space. It also sends a message from Washington to Moscow that the United States doesn’t see monitoring or disrupting Kremlin cyber activity as a priority.

No one knows where that ultimately leads. Trump and his Republican Party genuinely seem far less interested in countering Russia compared to other geopolitical (and domestic) priorities like trade tariffs and besting China in the development of modern technologies. They share ideological priorities, such as a reassertion of patriarchy and a hatred of progressive activists, with Moscow.

Trump’s team, especially Vance, have been explicit in their view that the best way to bring about peace in Ukraine is not through conventional hard power, but through economic arrangements that are essentially exploitative.

On top of that is the Department of Government Efficiency-led destruction of U.S. state capacity, alongside the comprehensive assault on counterintelligence services like the FBI, which Trump blames for prosecuting insurrectionists from the Jan. 6, 2021, attack on the U.S. Capitol. That suggests the United States will not even be seeking to gather, or capable of getting, the levels of intelligence that it has since the end of the Cold War. You can’t share what you don’t have.

In a best-case scenario, Europeans grit their teeth and get through the next four years, hoping that Trump is not sharing sensitive information with adversaries or keeping them in the dark too much. In a worst-case scenario, Europe is caught on the hop by something that its supposed closest ally could have warned it about—an escalation by Russia, for example.

Either way, it’s yet another can of gas being poured on a fire that threatens to burn down the bridge across the Atlantic. Even if we get through Trump’s second term relatively unscathed, there’s no guarantee that bridge will ever be rebuilt.