BERLIN — The CIA’s station chief here delivered an alarming piece of intelligence to Germany’s spy agency last year, according to German and U.S. officials: Russia was planning to assassinate the chief executive of Germany’s largest arms manufacturer.

The German government responded by surrounding Rheinmetall CEO Armin Papperger — whose company is a major supplier of munitions to Ukraine — with a security detail as large as the one assigned to the chancellor. German intelligence services then began scouring their own sources for more information on the plot, including whether Russia had operatives in place for such a brazen operation, the officials said.

But a year later, Germany’s understanding of the threat still consists almost entirely of what it was told by the CIA, the officials said, speaking on the condition of anonymity to discuss sensitive intelligence. The search involved all of Germany’s security services, one official said, “but we don’t have such information.”

The sequence underscores a level of dependence on U.S. intelligence that has persisted in Germany and other Western countries for years. Over the past several months, amid President Donald Trump’s return to power, that reliance is increasingly seen as a vulnerability.

Across Europe, security officials are contemplating scenarios that once seemed unthinkable: being cut off from U.S. intelligence by an administration seeking to punish or pressure allies; reduced intelligence gathering on Russia under a U.S. president who has a history of siding with the Kremlin; espionage relationships built over years undone by purges of U.S. intelligence officers and analysts accused of inadequate fealty to the president.

In interviews, current and former senior European security officials spoke with a shared sense of unease, facing a stream of Russian proxy attacks at a time when the continued flow of alerts from U.S. intelligence — like the one shared with Germany — suddenly seems less certain. Among the officials are senior security officials in Baltic, Nordic and Eastern European countries that have faced arson attacks, assassination plots and sabotage operations attributed to Russian proxies.

Papperger, meanwhile, remains under protection. A former German official described taking part in a recent hunting outing with the Rheinmetall executive and said at least six security operatives accompanied him, even into the forest. Papperger declined to comment for this report.

“America remains the global security superpower with more intelligence capabilities than anybody else put together,” said a former senior British official who worked closely with U.S. spy agencies. But the anxieties across Europe “are real,” the official said, because “America has decided to voluntarily plunge its own security agencies into crisis.”

U.S. officials said European worries are unfounded. A CIA spokesman said the agency “takes its international intelligence partnerships incredibly seriously and under Director [John] Ratcliffe is actively deepening them to further U.S. national security, counter adversaries around the world, and promote international stability.”

Anticipating an era of transatlantic uncertainty, European officials have adopted a dual strategy: doing what they can to preserve the U.S. relationship and keep the intelligence flowing, while embarking on the daunting task of finding ways to reduce their dependence on it.

In Germany, a country that has deliberately constrained the powers of its security services to safeguard against Nazi and Soviet-era abuses, the new coalition government led by Chancellor Friedrich Merz — who will meet with Trump at the White House on Thursday — has signaled plans to boost spending on spy agencies and remove certain barriers to more aggressive operations.

“We have decided to boost air defense, drone technology, intelligence, satellite reconnaissance and all aspects of modern warfare,” said Stefan Kornelius, who represents Merz as the German government’s chief spokesman.

America’s closest ally, the United Kingdom, has cultivated members of Trump’s security team with royal treatment. Last month, Ratcliffe, FBI Director Kash Patel and FBI Deputy Director Dan Bongino — previously a right-wing podcaster — dined with King Charles III and British Prime Minister Keir Starmer at Windsor Castle.

They were joined by other spy chiefs gathered in London for a summit of the “Five Eyes” partnership, an exclusive intelligence-sharing arrangement involving the United States, the U.K., Canada, Australia and New Zealand. Charles used the occasion to praise the ongoing value of the Five Eyes alliance, officials said, which Trump trade adviser Peter Navarro suggested dismembering earlier this year with a proposal to expel Canada. The FBI declined to comment.

European security officials said their fears of an abrupt cutoff from U.S. intelligence have subsided since March, when the administration shocked allies by temporarily withholding satellite images and other wartime data from Ukraine. Instead, European officials said their concerns have shifted to how much damage U.S. spy agencies might sustain amid perceived purges being carried out by Director of National Intelligence Tulsi Gabbard — who had not previously held a senior national security position — and other Trump loyalists.

In April, Trump fired a four-star general who had served as director of the National Security Agency, the nation’s premiere cyberespionage service, at the urging of a far-right activist who once called the Sept. 11, 2001, terrorist attacks an “inside job.” A month later, two of the nation’s top intelligence analysts were forced out after producing a classified assessment that undercut Trump’s rationale for using a rare national security law to deport alleged Venezuelan gang members.

Gabbard’s office denied any deterioration in relations with allies. “The truth is, DNI Gabbard has just returned from her third international trip in three months and has met with more than 80 of our foreign partners from every region of the world, demonstrating the strength of our bilateral relationships,” said ODNI spokesperson Olivia C. Coleman.

Referring to the firings, a U.S. official said that Gabbard “will continue to remove people from the [Intelligence Community] workforce who put their own personal or political interests ahead of our mission.”

The ousters rattled Western security officials already struggling to comprehend other chaotic episodes, including the sharing of U.S. military strike plans on the Signal messaging platform, a suspension of cyberoperations against Russia, and reported White House demands for spy agencies to provide intelligence that would support Trump’s pledge to seize Greenland, an autonomous territory of Denmark.

Bewilderment over America’s course has become a constant subject of sidebar conversations at security conferences in Europe and elsewhere — generally out of earshot of U.S. officials in attendance.

“Everybody is trying to think through contingencies,” said a senior official with the intelligence service of a Baltic nation. Even if there is no formal White House directive to reduce cooperation, the official said, there is fear that distractions and departures will mean that warnings and tips European services have come to expect “might kind of disappear.”

At an April gathering of European intelligence chiefs in Brussels, officials weighed mostly meager options for managing the U.S. partnership, according to participants.

“There’s a tension there,” said a European diplomat. The Trump administration’s volatility “makes it difficult to chart a clear course,” the diplomat said. But given shared interests and unmatched U.S. capabilities, there is no choice but “to continue to cooperate.”

France, whose formidable intelligence capabilities make it less U.S.-dependent than others, has for years urged allies to fortify their own capabilities and deepen continental cooperation. But truly Pan-European collaboration remains unrealistic, officials said, given disparities in resources, barriers to sharing data and concerns about the pro-Russian leanings of member states including Hungary.

When Konstantin von Notz, the chairman of the German parliament’s intelligence oversight committee, floated the idea of creating a “Euro Eyes” spy network in March, he was urged by current and former German intelligence officials to drop the idea, officials said, in part out of fear that merely mentioning it would draw the ire of Trump officials.

In an interview, von Notz, a member of Germany’s traditionally pacifist-leaning Greens party, described bolstering Berlin’s intelligence capabilities as imperative. “We have to be more grown up,” he said. “We have to invest more money, take care of our own stuff and then we are probably better partners with the U.S. and the Five Eyes as well.”

The CIA’s warning about the Russian plot against Papperger was one of several incidents in which Germany’s security services learned of a terrorist plot or other internal threat only from U.S. sources, officials said. Frustration with this pattern came to a head earlier this year when U.S. security officials secretly met with advisers to Merz and catalogued German failures to detect threats on its own and share information fast enough across its patchwork of police and security services, according to participants.

“The Americans rightly perceive themselves as a source for information for us on everything from child pornography to terrorism and are not happy with the fact that if it weren’t for them we would be blind,” said a German security adviser who participated in the meeting. He declined to identify the affiliations of the U.S. officials involved, except to say that they were “from a variety of agencies involving both intelligence and security.”

The stakes for Germany have risen since Russia’s invasion of Ukraine.

Germany’s role as a key arms supplier to Ukraine — and an expected source of military hardware to European nations seeking to bolster their defenses against Russia amid questions about U.S. commitment — has made it a target of Russian sabotage and proxy attacks, according to U.S. and German officials.

Last month, German police arrested three Ukrainian nationals accused of working for Russian intelligence to ship packages with GPS trackers to addresses in Ukraine, a step that German authorities suspect was in preparation for sending explosives targeting transport routes. A similar suspected Russian operation last year involved incendiary devices on cargo planes, including one that caught fire at a distribution hub in Leipzig. Authorities have arrested other suspects tied to alleged Russian operations involving espionage, arson or sabotage.

Germany’s intelligence services, including its foreign spy agency, the BND, have substantial capabilities, including eavesdropping access to one of the world’s major communications hubs near Frankfurt, officials said. But Germany lacks key platforms — its first spy satellites are expected to be deployed later this year — and its agencies are also governed by data privacy protections and oversight regimes that are among Europe’s most expansive.

“We have more oversight bodies than intelligence services,” said Jan-Hendrik Dietrich, co-director of the Center for Intelligence and Security Studies in Munich. As a result, Germany has fostered a system that Dietrich described as “absurd.”

“Information from the U.S.A. or Israel was welcomed,” he said, even as “politicians were keen to boast publicly about how well the intelligence services were restricted.”

The coalition government led by Merz has already scrapped long-standing barriers to boosting defense and intelligence spending, and signaled plans to mount new legal challenges to constitutional limits. Officials described this as an effort that could take years and reduce Germany’s dependence but never match U.S. capabilities.

Germany can spend billions on new platforms and combine resources with European partners “to have better coverage for limited theaters,” said Gerhard Conrad, a former senior BND official. But “how can we substitute for huge U.S. capabilities built up over decades? There is no chance for anybody to rival that on a global scale.”