Never has there been so much interest in a NATO summit in Brussels. Why? Because when Donald Trump rolls into town, anything could happen.
There are so many big issues on the military menu at this week's gathering, ranging from Russia and Ukraine to Afghanistan. But, the question is, will everything be overshadowed by money? Donald Trump's demands for other governments to cough up more cash.
Protesters take to streets
Trump's upcoming visit to Brussels hasn't gone unnoticed in the de-facto European capital. Crowds of demonstrators demonstrated in the city at the weekend.
"We don't want our money, or taxpayers' money, to be invested in war or war policies. But we want it to be invested in education, in our pensions, in the tackle against climate injustice," said protest organiser Véronique Coteur.
Trump comes to Brussels having pulled out of the Iran nuclear deal and slapped tariffs on exports of EU metals - with a threat of more to come on cars.
And his message to NATO members? "Start paying your bills" - as he's long demanded.
"President Trump is a bit of a wildcard for this summit," said Kristine Berzina, from The German Marshall Fund of the US.
"Everything has been telegraphed to show that this is going to be complicated, there are going to be tough conversations. So I think everyone is coming in prepared, knowing that that will happen."
Multiple military challenges
NATO's facing pressing, military challenges right now. The Baltics, Middle East and Afghanistan to name a few.
And then there's the question of Russia. But how much does Moscow fear NATO?
Andrey Kortunov, Director General of Russian International Affairs Council, told Euronews: "Improving troop mobility gives the bloc extra opportunities. This is something that Russia can be concerned about in the medium term. It can also be worried by the ongoing technical re-equipment of NATO forces."
And from Brussels, warning shots are already being fired over Trump's relationship with Moscow.
"It is always worth knowing who is your strategic friend, and who is your strategic problem," said Donald Tusk, European Council President.
The US has sent mixed messages over Russia. The administration's intensified a military build-up in Europe, while also failing to coordinate on new sanctions on Moscow last year.
Euronews' Damon Embling reported from Brussels: "Whatever Trump says about Russia here in Brussels will come ahead of his meeting next week in Helsinki with Vladimir Putin.
"Moscow could capitalise if there's a disastrous summit, one that has the potential of being even messier than the G7 in June."