What’s an ally good for? If you’re a large and wealthy country like the United States, or even a small and wealthy country like Sweden, the answer’s not “cash flow.” Sweden pays €3.3 billion ($3.9 billion) into the EU budget each year – and only receives €1.7 billion in EU funding. Poland, by contrast, contributes only €3.6 billion and receives €10.6 billion. A terrible deal for Sweden, President Trump might say. But here’s the thing about allies: while you may not need them on most days, they can help you in a pinch. This month Sweden has been fighting devastating forest fires – so devastating that they have overwhelmed the country’s first responders and armed forces. So EU allies, including Poland, have come to the rescue. Donald Trump might want to pay attention.

It was a moment for the European history books. On July 21, 144 Polish firefighters traveling in 29 fire trucks arrived in the southern Swedish port of Trelleborg and began their journey towards the country’s north, where out-of-control forest fires had exhausted the Swedes’ own capacities – even though the Swedish Home Guard had come to the aid of fire brigades from across the country. In each town, at each highway bridge the fire-red Polish convoy was cheered on by local residents; the Poles honked their firetrucks’ horns in return. #TackPolen (“thank you, Poland”) trended on social media.

Other countries, too, pitched in to help the Swedes. Italy immediately dispatched water-bombing planes, which were soon joined by French aircraft. Norway sent nine firefighting helicopter; Germany sent five; Lithuania, one. Germany also sent 46 firefighters (and 33 trucks), while France sent 50 firefighters and Denmark another 40. Finland, too, sent firefighters, while Portugal pitched in with a water-scooping aircraft.

It was a true show of force for the European Union – in fact, the largest mission ever coordinated by its Civil Protection Mechanism, a voluntary framework to which EU members (as well as several other countries, including Norway) belong, and which coordinates civil emergency response. “This has been the hottest months in 262 years, and you can’t maintain firefighting capacities for such extremes, though it’s safe to say that we should have better early-detection capabilities,” said Johan Wiktorin, Director of Intelligence at PwC Sweden and a former army officer. Last week, Sweden asked NATO for help, as EU allies had to assist Greece as well. Sweden’s fellow non-NATO member Finland offered ground forces.

Though members of the EU Civil Protection Mechanism promise to help one another, there’s no legal obligation to do so, just as NATO member states are not obliged to assist one another fighting forest fires. Warsaw, for example, didn’t have to make scores of firefighters available to the Swedes – and after having been repeatedly criticized by the Swedish government for current policies perceived as illiberal, it might have been forgiven for not lending the Swedes a helping hand. The same goes for Italy, whose government is also a frequent subject of Swedish criticism. Indeed, though EU rules oblige recipients of civil emergency assistance to reimburse their Good Samaritans, it would be easier for most countries not to bother with the assistance in the first place.

But here’s the thing about alliances: goodwill goes a long way. As climate change worsens, Italy and Poland are likely to be hit, too. It stands to reason that Sweden will be the first country to come to their aid. Or to the aid of Germany, which doesn’t have a single firefighting airplane. To paraphrase the Blues Brothers: Everybody needs somebody to help them in case of natural disasters (or military aggression). “Not even the most powerful person or country can accomplish everything or as much alone, and that goes for the United States,” said Azita Raji, a former U.S. ambassador to Sweden. “It’s both wrong and foolish to ignore the power of the force multiplier that is our alliances. We see that power in the example of Sweden.”

Indeed, the Swedish forest fires and the European solidarity they unlocked stand in sharp contrast to the Donald J. Trump school of international relations, which holds that alliances are mostly a waste of money and primarily benefit freeloaders. The U.S. doesn’t even need NATO, the president suggested this month. He is, of course, right that NATO’s European member states should spend more on defense, and for the past four years they have been increasing their spending. One could even make the case that the mighty U.S. military can accomplish most of its tasks alone, or by means of hastily arranged “deals” with other countries. Moreover, adherents to the Trump school of thought would point out that countries shouldn’t recklessly cut their preparedness to the point where they need outside assistance in a worst-case scenario.

But the Swedish forest fires show that alliances are not a mercantile arrangement where each country receives the exact monetary value of what it puts in. One of the many values provided by alliances is that they, in fact, save money. Sure, Sweden does need to up its game, but for every country to be fully armed against any natural disaster, or indeed military confrontation, would be prohibitively expensive. And though allies may disagree on plenty of things – say, the independence of the Polish judiciary – they benefit from working together. The Swedish forest fires have brought home to many Swedes the benefit of alliances. “It has created a more nuanced view of the EU,” Wiktorin pointed out.

The fires also raise the question of who would come to America’s aid next time it needs help. Last time Washington cabled for large-scale assistance, after 9/11, its NATO and other European allies played the role of “Polish firefighter” and generously came to the aid of George W. Bush. “A lot of preparation – for example legal aspects, processes and financial mechanisms — goes into making partnerships and alliances work,” Wiktorin said. “The closer the cooperation, the better the chances are of getting effective help when needed.” Kissing a foreign leader after having insulted his organization, as Mr Trump did with European Commission President Jean-Claude Juncker, doesn’t equate a durable friendship. A kiss is just a kiss. (Play it again, Sam.)

None of this, of course, is news to diplomats. Indeed, enduring friendships – especially formal ones, that is: alliances — are key to successful diplomacy. Alliances are, as Mr. Trump might put it, a tremendous deal.