Article 5 of the NATO Treaty contains the following language: “The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defense recognized by Article 51 of the Charter of the United Nations, will assist the Party or Parties so attacked.” Given its position as the strongest military power in the world, the other NATO countries have always looked up to the U.S. as the leader of the alliance. That “first-among-equals” status entails some heavy responsibilities, but it has also conferred some privileges on America over the decades.

Until recently, it was unthinkable that any American president would even hint at the possibility of the U.S. not abiding by Article 5. It appears though that with President Trump, nothing is taboo. He has publicly said recently that in some circumstances, he cannot guarantee U.S. military assistance to other NATO members. That statement was so shocking that it prompted me to take a deeper look into what drove him to make it. What I found led me to conclude that while his pronouncement about Article 5 was reckless and unfortunate, he actually had a good reason for issuing that threat.

In 2006, NATO defense ministers agreed that each alliance member should spend no less than 2 percent of GDP on defense annually. Following Russia’s annexation of Crimea in 2014, NATO heads of state formally committed to the target. Three years later, when President Trump entered the White House for the first time, only four of the then 30 members were in compliance. Mr. Trump repeatedly called for increased defense spending within the alliance during his first term.

That had some effect. The number of countries meeting the 2 percent target had increased to nine by the time Trump left office in early 2021. But the trend soon started to reverse. Only seven nations met the goal in 2022. It took Russia’s invasion of Ukraine that year to dramatically change the picture. In 2024, 23 of the alliance’s members are expected to have met the target.

 The U.S. has consistently been the standout performer. In 2014, it spent 3.7 percent of GDP on defense. Estimated spending for 2024 is slightly lower at 3.38 percent. Some of the worst freeloaders in 2014 were Germany, Italy, Canada, Belgium and Spain. Germany and Italy spent 1.2 percent of GDP that year, with the others spending one percent or less. To Germany’s credit, it met the goal in 2024, devoting an estimated 2.12 percent of GDP to military spending. The expected 2024 tallies for Italy (1.49 percent), Canada (1.37 percent), Belgium (1.3 percent) and Spain (1.28 percent) still fall far short of the target. By share of GDP, Poland, with a projected 4.12 percent for 2024, is currently the highest spender.

Published data show that last year, aggregate NATO spending on defense was approximately $1.5 trillion. With its estimated 2024 outlays for the military amounting to $968 billion, the U.S. alone accounted for 66 percent of that total. Quite clearly, many of the remaining 31 members of the alliance are contributing nowhere near enough to the collective defense budget. President Trump is therefore right to be upset that Canada and most of the European members of NATO have been freeloading for too long.

There are two ways to think about this long-running contentious debate between the U.S. and its NATO allies over defense spending. One could argue that the slackers were actually doing the right thing by diverting resources from the military to boost expenditures on social programs. After all, with the end of the Cold War, the global landscape had become so tranquil that it seemed to be a logical choice. The few hot spots around the world during the last three decades were no more than smoldering embers that were easily managed with modest military capabilities.

We have had that debate here in America over the last several years. Many people, especially on the left of the Democratic Party, have consistently argued that we have been spending too much on defense at the expense of social programs. But that thinking, here at home and elsewhere within NATO, now appears to have been quite naïve. The war in Ukraine, and China’s increasingly bellicose behavior in its backyard, represent infernos that require heavy-duty fire engines to suppress.

President Trump should be given a lot of credit for consistently and vociferously pointing out what many people apparently failed to see. The world indeed continues to be a dangerous place, and the best way to keep our nation and our allies safe is to, collectively, maintain a strong military. For me the validation of his worldview is another lesson on the importance of listening with humility. Because of the way the president talks, lots of people, including me, often don’t take him too seriously. But when we reflexively dismiss voices like his, we risk missing some blind spots for which our attention may actually be crucially needed. And I have to grudgingly admit that on this issue, perhaps some of his rudeness was useful. That is what it takes sometimes to get people’s attention.

There has been a lot of reporting in recent weeks indicating that the other NATO members are finally taking the issue of defense spending seriously. Germany and the U.K. have both announced that they will significantly boost their military budgets over the next several years to beef up their defense capabilities. Every member of the alliance realizes now that the stakes are quite high, making it highly likely that more countries will start to bear more of the responsibility than they have done in the past.

A strong NATO remains the best defense against the dangerous slide into authoritarianism that we are witnessing around the world today. President Trump should not undo all the good work he has done to strengthen the alliance during his time in office. Worryingly, he seems to be doing just that with some of his unfortunate statements.