Trump just committed to NATO’s Article 5. Finally.

President Donald Trump stunned both his own aides and the leaders of America’s closest allies in late May when he departed from his prepared remarks and cut a sentence explicitly saying he was committed to the mutual defense provision at the heart of the NATO military alliance.

On Friday he went off-script again — but this time to casually say that he was, in fact, committed to Article 5 of the NATO charter. That completed a stunning transformation for Trump, who began his campaign for the presidency by trashing NATO as obsolete only to now say he sees it as a capable military partner and would come to the defense of any member nation attacked by Russia.

“I’m committing the United States — and have committed — but I’m committing the United States to Article 5,” Trump said in a press conference alongside visiting Romanian president, Klaus Iohannis.

NATO allies — and Trump’s own staff — would be forgiven for feeling a sense of whiplash after Trump’s changes of mind on the alliance’s relevance over the past two years.

Still, they are surely glad the president of the United States has come around to fully endorse NATO’s main reason for being.

During the campaign, Trump called NATO “obsolete.” He later reversed his opinion in office, wrongly claiming the alliance was now willing to fight terrorism because of Trump’s demands it do so (NATO has actually been officially committed to battling terrorism since the 1980s, and has deployed troops to Afghanistan since the US-led war there began in 2001).

He has also bashed allies for not spending enough on defense, saying they need to contribute to the alliance’s 2 percent spending benchmark. Some countries are already starting to do that. Trump is taking credit for the spending uptick, but it was in the works way before he became president.

But if Trump liked NATO, he didn’t let his fellow allies know it. In a May 25 speech in Brussels, Trump refused to commit the US to Article 5, even though the following phrase was originally in his prepared remarks:

“We face many threats, but I stand here before you with a clear message: the US commitment to the NATO alliance and to Article 5 is unwavering.”

Trump took it out, completely blindsiding his top national security aides, like Secretary of Defense James Mattis and National Security Adviser H.R. McMaster, who had thought that phrase would remain in the president’s speech.

That’s another reason Trump’s Article 5 statement today is so jarring: He decided to commit to America’s most important alliance in an answer to a question that hadn’t even explicitly asked about it, and wasn’t in his prepared statement.

Trump has been known to surprise his aides by offering contradictory policy statements before, though.

Earlier today, Secretary of State Rex Tillerson asked Middle Eastern countries to quell their diplomatic stand-off with Qatar. But Trump, before his NATO comments, trashed Qatar for its terrorism support — putting him at odds with his top foreign policy aide within the span of a few hours.

So, Trump made a big policy pronouncement, seemingly off the cuff and with no warning. Many are surely happy, relieved, even, while feeling confused at the same time.