President Donald Trump’s national security team was blindsided last month when he strayed from a speech they’d approved that affirmed the United States’ commitment to Article 5 of the NATO alliance, according to a Monday report in Politico.

Three of Trump’s top advisers and cabinet leaders—National Security Adviser H.R. McMaster, Defense Secretary Jim Mattis and Secretary of State Rex Tillerson—had all worked on the address Trump was to deliver at NATO headquarters in Brussels, and they included language reaffirming the U.S. commitment to Article 5, the provision in the NATO treaty about collective defense, per Politico.

And they were not told that Trump wouldn’t mention Article 5, only finding out as he delivered the address on May 25, Politico reported.

National Security Council spokesman Michael Anton did not deny this account, according to Politico.

“The president attended the summit to show his support for the NATO alliance, including Article 5. His continued effort to secure greater defense commitments from other nations is making our alliance stronger,” he told Politico.

It’s unclear whether Trump removed the section of the speech himself or if he was persuaded to do so by his chief strategist, Steve Bannon, and senior policy adviser, Stephen Miller, per Politico.

European leaders were surprised that Trump did not reaffirm his commitment to Article 5, especially since the New York Times had reported that the President would use the address to endorse that provision in the NATO treaty.

The omission left Trump’s advisers scrambling to ensure that the United States is committed to Article 5.

“I think it’s extraordinary that there would be an expectation that the President would have to say explicitly that he supports Article 5. Of course he does,” McMaster told reporters after Trump’s speech.