NPR. This is The Indicator from Planet Money. I'm Adrian Ma. And I'm Waylon Wong. The Pentagon's decision to pull some American troops out of Germany represents a fresh chill in the relationship between the U.S. and its European allies in NATO. The North Atlantic Treaty Organization is one of the pillars of the post-World War II global order. And historian Heather Cox Richardson says it has yielded huge benefits for the U.S. and the rest of the world. This is a defensive alliance that has this extraordinary payoff. Look even at hand now at how much the United States of America is spending in Iran alone. That's a billion dollars a day. So if you think about this not as a tit for tat and you think of it more as a concept of how the world should operate, NATO is really cheap. President Trump, however, does talk about NATO like it's a tit for tat. He was once quoted as saying at a campaign rally, if they're not going to pay, we're not going to protect. And that makes NATO sound more like a protection racket than a strategic alliance. So is that what NATO is? Today on the show, we examine Trump's view of NATO, how this long-standing alliance is becoming strained, and how the U.S. could pay the costs, both politically and economically, for those frayed relationships. If the brain is like a computer, then Kyla Madonna-Kennies was crashing. The room was spinning and I was shaking, but only on one side. Doctors couldn't see anything physically wrong with Kyla's brain, with the hardware, so to speak. The problem was with the software. And the condition she was eventually diagnosed with is called functional neurological disorder. To learn about this invisible illness, listen to Shortwave on the NPR app or wherever you get your podcasts. Historian Heather Cox Richardson writes a newsletter called Letters from an American. It has around 3 million subscribers. Her focus is explaining how we got to our current moment. And to understand NATO, she says, you have to put yourself in the mindset of people who endured the horrors of two world wars. They wanted to make sure it never happened again And they were willing to put everything on the line to make sure it never happened again to create a safe world for their children and grandchildren and other people children and grandchildren So what they do is they think how are we going to do this How leaders of the U.S. and its allies did this was through three basic pillars. Number one, free trade enabled by freedom of the seas. That means people and goods can flow safely between countries. Yeah, we don't have to worry about our imported athleisure or smartphones getting plundered at sea. Our stretchy pants are safe. Important. The second pillar is international cooperation through exchanging culture and values. And the third is collective security. These World War II-era agreements produced organizations like the World Health Organization and the International Monetary Fund. NATO was also born during this time. And the core of NATO is its famous Article 5, that an attack on one member is an attack on all of them. It's only been invoked once, when NATO allies rallied to support the U.S. after 9-11. This was a treaty to try and stop there being a need to fight, which is actually really cool if you think about it. It's important to emphasize, it doesn't mean there's never war. And it doesn't mean people all get along either. It means they don't go to war in such a way that they create a world war. That was central to American prosperity and American power after World War II and crucial to it. President Trump, however, has characterized NATO as a system where European countries are shirking their responsibilities. And this is a worrying signal for Nikki Akani. She's a fellow at the NATO Defense College, which is NATO's research arm. Although Nikki says she doesn't speak on behalf of the alliance. I'm a specialist on warnings when they fail, when they work. And that's obviously relevant for institutions like NATO. Wow, a specialist on warnings. Are you in a constant state of alert then? It's true that if you write about warnings that go unheeded, you tend to see them everywhere. She sounds so calm and collected. I don't know how she does it. She's a pro. This is why people with my disposition are not experts in warnings. No, just be walking around going, warning, warning. like that old TV show that I've only seen clips of. The warning signs for the U.S.-NATO relationship have been pretty clear Trump has complained about NATO since his first term President Trump has sometimes spoken about certain allies as being delinquent as if they owe money And he suggested that if countries NATO countries, don't spend enough on their defense, the U.S. might not defend them. And the logic is them becoming, if you pay, you get protection. And if you don't, you are not protected. So it almost becomes like NATO is a fee for a service, like a subscription where if you pay, you get the service. And if you don't, you do not. NATO is, in fact, not a Netflix for transatlantic security. It is an organization based on mutual assistance. And there are two main components of NATO's funding. The first is the organization's common budget. It's $5 to $6 billion a year, and each member pays into that pot in proportion to their size. That pays for things like NATO headquarters, the communication systems. The real practical things NATO needs to run as an organization. Bigger countries pay more and smaller ones pay less. And everyone has been paying that bill. The second aspect of NATO funding is national defense spending. This is what Trump has zeroed in on. Members commit to spending a percentage of their gross domestic product on their own defense. So this is money that countries spend on themselves, with the understanding that these resources can be used for the good of the whole alliance. So let's say NATO is a group project in school. Each student spends money on supplies that they need for themselves, but that they can also share with the whole group. So one kid buys scissors, another kid buys markers, but one kid buys glue sticks and glitter and googly eyes. Right. And Nikki says there's another thing. It matters what that percentage of GDP gets spent on. If that money goes towards, say, paying military pensions, then it doesn't really help NATO if there's an attack on one of its members. It's not about the money you spend, but what you spend it on and what that allows you to do in a crisis. And this is where there's some truth to the recent statements from the White House, because even if European countries are increasing their defense spending, it's still the U.S. that provides a large share of those high-end capabilities. Nikki says the U.S. has invested in crucial infrastructure that benefits other NATO members. These are capabilities like high surveillance systems aircraft that can refuel mid and nuclear deterrence And so to go back to our group project analogy it would be like if one student shows up with a poster board but the project doesn need poster board Meanwhile, another student buys a 3D printer. And that's what the group actually needs to complete the project. The NATO defense spending commitment used to be 2% of GDP. It was upped to 5% last year amid intense pressure from Trump. And Nikki says it's this pledge that gets entangled in controversy. One reason is that until recently, the U.S. was one of the only NATO members that actually hit that original 2% benchmark. In fact, historically, if you added up what other allies spent on defense, it was less than half of what the U.S. spent. Nikki says there was a time when the U.S. didn't mind this imbalance in spending. It believed it was in its own best interest to protect its European allies. That thinking has changed. Nikki says the Trump administration sees security as less of a group project and more of a transaction between countries. Pay up, support the U.S. and Iran, or we will withdraw from NATO or we'll pull troops from Germany. Trump has threatened to do the same in Spain and Italy. We reached out to the White House and Press Secretary Anna Kelly said, quote, Europe benefits tremendously from the tens of thousands of United States troops stationed in Europe. Yet requests to use military bases in order to defend American interests were denied, unquote. She added that the president will never allow the U.S. to be taken advantage of by so-called allies. Historian Heather Cox Richardson says Trump's stance isn't good for the U.S., politically or economically. What really makes my head explode is that we have literally on the table the proof that from World War II to the ascension of Donald Trump, the system for keeping the United States safe and for keeping the United States economy strong worked. European allies are not waiting for Trump to change his mind. Some European leaders, including a former secretary general of NATO, are already talking about creating another security alliance without the U.S. This episode was produced by Corey Bridges with engineering by Jimmy Keely. It was fact-checked by Sierra Juarez. Kagan Cannon is our show's editor, and The Indicator is a production of NPR.