As Donald Trump headed to Brussels for a NATO summit Tuesday morning, he made it really clear that it’ll be a confrontational meet-up.

Just as he was preparing to board Air Force One to fly across the pond for a convening of the 29 NATO states, the president reminded U.S. allies that they’re not spending nearly enough on their military. Back in 2014, NATO states committed to try to gradually increase their military spending to 2 percent of their gross domestic product by the year 2024. Many aren’t there yet, and Trump’s getting impatient.

The U.S. does indeed spend more than most of its allies on its military budget — 3.1 percent of the U.S. GDP went towards the military in 2017, according to World Bank data, though that figure has been declining in the last decade. Germany and Canada, by contrast, spend only 1.2 percent of their GDP on their militaries.

And Trump’s not happy about that. His administration sent strongly-worded letters to states — Germany, Canada, and Belgium, among them — that he thought were lagging behind, telling them, in so many words, to shape up and start spending on their militaries, according to the New York Times. The Trump administration has said that 16 NATO member states are on course to meet their defense spending goals, but it hasn’t specified which countries.

The NATO chief, it turns out, is actually pleased that Trump is cracking the whip on other NATO member states. Secretary-General Jens Stoltenberg thanked Trump during a White House visit back in May.

“Let me thank you for the leadership you show on the issue of defense spending because it is very important that we all contribute more to our shared security,” Stoltenberg said.

“Do you give me credit for that?” Trump asked.

“You have helped to do that,” Stoltenberg told him.

After Trump’s NATO visit, he’ll head to London, where he’ll be greeted by an enormous, orange Baby Trump blimp, that will fly over Parliament for two hours while Trump’s in town, and a population that dislikes him so much that they’re willing to listen to Green Day’s 2004 song ‘American Idiot,’ which is objectively a bad song, to prove it. The song, originally inspired by President George W. Bush’s administration, is topping charts in the U.K. in the run-up to Trump’s visit.