As Russia moved closer to invading Ukraine nearly three years ago, the United States and its allies took the extraordinary step of declassifying and sharing intelligence to expose Moscow's plans.
Information flew across the Atlantic from US spy agencies to Nato and Western partners showing that Russia was poised to launch the biggest attack on a European country since World War II.
It was designed to muster support for Kyiv, and on the strength of the US warning, some nations sent weapons to Ukraine, which moved some equipment out of the range of Russian strikes.
Now, officials are bracing for a potentially changed security landscape under President Donald Trump. He has criticised America's allies and lambasted its intelligence agencies. He's been accused of disregarding secrecy rules and hoarding classified documents.
Tulsi Gabbard, Trump's pick for director of national intelligence, has parroted Russian propaganda while his nominee to lead the FBI, Kash Patel, has promised changes that could significantly curtail the flow of intelligence to America's friends. Both are expected to face sharp questioning from lawmakers during confirmation hearings Thursday.
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The Associated Press spoke with 18 current and former senior European and US officials who worked in Nato, defence, diplomacy or intelligence. Many raised questions and concerns about Trump's past relationship with America's spies and their ability to share information at a time of heightened terror threats and signs of greater cooperation between US adversaries.
The importance of trust The US and its allies routinely share top-secret information, be it about potential terror threats, Chinese cyberattacks or Russian troop movements. America's closest intelligence partners are New Zealand, Australia, Canada and Britain, and it often shares with other nations or sometimes even adversaries when lives are at stake.
In July, the US helped foil a Russian plot to assassinate the head of a German arms manufacturer that produced weapons for Ukraine. In August, the CIA said it provided intelligence to Austrian authorities that allowed them to disrupt a plan, allegedly inspired by the Islamic State group, to attack a Taylor Swift concert in Vienna.
Cooperation particularly between the US and the UK is strong and robust enough to withstand some turbulence at the political level, said Lord Peter Ricketts, former UK national security adviser and current chair of the European Affairs Committee of the upper chamber of the British Parliament.
However, any strong intelligence relationship is underpinned by trust, and what if trust isn't there? Ricketts said.
There was some skepticism about US intelligence ahead of the invasion of Ukraine due to the faulty American information that led to the invasion of Iraq in 2001, said Oana Lungescu, a fellow at the Royal United Services Institute in London and formerly Nato longest-serving spokesperson.
But when combined with information from its security partners, America's remarkable intelligence" enabled the Nato alliance to raise the alert about Russia, Lungescu said.
European leaders are working to convince Trump's administration that threats on the continent also are relevant for the United States.
There shouldn't be much debate, said former US Ambassador to Russia, Mike McFaul, who said there's a direct relationship between US intelligence sharing and national security. He noted that US authorities have warned of escalating terror threats.
One of our great advantages is that we have incredible intelligence capabilities and we have allies that we share that with it's a force multiplier for us, said McFaul, who now teaches at Stanford University. We'll lose that if we're no longer considered trustworthy.
The Trump team has an open mind and is in a listening mode, Norway's Prime Minister Jonas Gahr Stre said, adding that was a good sign because when you come in with a new administration in a very eventful, rapidly changing environment, getting on the same footing is a challenge.
Predicting Trump's moves, however, is difficult. He has criticised Nato allies for not spending enough on defence. He even suggested he would encourage Russia to invade countries that didn't pay what he thought they should. But he didn't follow through on the threat.
Last time it didn't turn out so badly: He was going to throw Nato under the bus, but he didn't do that," former US Director of National Intelligence John Negroponte said. "The rhetoric turned out to be transactional.
Spokespeople for the White House and Gabbard did not respond to questions about Trump and his nominees or how they planned to handle intelligence sharing with America's allies.
Nato members have hiked their defence spending as Trump has demanded and the alliance is now bigger than before, with Sweden and Finland joining after Russia invaded Ukraine.
There is a big risk of continuing to take American support for European, Nato countries ... and defence of Ukraine for granted, said Swedish Prime Minister Ulf Kristersson.
But it would also be risky to assume the US is simply leaving. On that question, Kristersson said, the jury is very much out.
Concerns about Trump's intel picks Trump's choice of Gabbard to oversee more than a dozen intelligence agencies has alarmed lawmakers from both parties and many current and former intelligence officials. Gabbard, a former Democratic congresswoman who later became a Trump ally, met since-deposed Syrian President Bashar Assad in 2017 in Damascus and has promoted Russian propaganda about its invasion of Ukraine.
If confirmed, Gabbard would have the power to declassify information and direct some intelligence sharing with allies.
A European intelligence official, who spoke on condition of anonymity to discuss sensitive matters, said that while there is concern around some of Trump's nominations, there is no reason to think we can't trust them because of who is in power.
The official suggested nominees like Gabbard and Patel haven't heard all the facts yet and could grow and learn when presented with the full picture.
With thousands of professionals working in a multitude of agencies, the day-to-day operations of America's spy services may look very similar under the Trump administration. And there are safeguards, current and former officials told the AP, that include agencies sharing intelligence but not sources.
But those in top positions will have a huge impact if they lead to staff departures, curtail longstanding surveillance programs as Patel has suggested or politicise their offices in ways that can be exploited by Moscow and other adversaries.
The task for Europe is to convince everybody to focus on Russia, the real troublemaker, the intelligence official said.
Alongside Gabbard, Patel has rattled intelligence insiders in the US and elsewhere because he's criticised surveillance programmes like the Foreign Intelligence Surveillance Act, which US authorities use to keep tabs on suspected spies and terrorists overseas.
The United States shared intelligence gathered through that law with Russia when public safety was at stake, passing along a warning before a deadly concert attack in Moscow in March that killed 145 people. It is not clear if Moscow tried to act on the warning.
Allies heavily depend on US intelligence The European Union must be realistic that if the US is reducing its participation in Europe, European members have to be ready to fill any gap, said former Finnish President Sauli Niinisto, who has called for the 27-nation bloc to create its own intelligence agency.
Many global tech and communication firms such as Google, Apple and Microsoft as well as Elon Musk's X are based in the US, giving American law enforcement and spy agencies an advantage over their foreign counterparts, which may lack the political or legal means to obtain information.
Niinist hosted a summit between Trump and Russian President Vladimir Putin in 2018, in which Trump openly questioned his own intelligence agencies' finding that Russia meddled in the 2016 U.S. election to his benefit, restating Putin's claim that Moscow was not involved.
Niinist, whose country borders Russia, described his discussions with Trump while in office as clear, open and frank.
I tried to tell him: We need you, but you need us, too,' Niinisto said.
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