(CNN) The big takeaway of the so far bad-tempered NATO summit is that President Donald Trump has little time for the alliance and a thin appreciation of the track record and historic purpose of an organization that has kept the peace and preserved Western democracy since World War II.

He has given no sign he sees the alliance as other US presidents did, as a way of projecting American power, fortifying democracy, containing German expansionism and holding Russia at bay on a continent where twice last century, thousands of American boys went to die.

Instead, he appears to view it more like a contracting service, in which US allies should be paying far more in cash for the privilege of being America's friend. If he sees any flow-back benefit to membership for the United States, the President rarely mentions it.

"I felt the President treated the NATO allies almost with contempt," former US Ambassador to NATO Nicholas Burns told CNN's Erin Burnett Wednesday after a day in which Trump berated US partners over defense spending and singled out Germany for particular scorn.

"It is important that we not normalize this. He is the first American president since Harry Truman ... to not believe that NATO is central to American national security interests."

With such attacks, Trump also often appears to be doing Russian President Vladimir Putin's work for him, by opening divisions in the transatlantic alliance and berating NATO partners. It's a move even more curious ahead of Trump's Helsinki summit scheduled for Monday with his Russian counterpart.

The question with which NATO leaders must wrestle as the summit ends is whether Trump's clear and public doubts about the alliance's purpose matter.

Trump signed off on a robust set of summit achievements on Wednesday via a communiqué that condemned Russia's "aggressive" actions and reaffirmed Western values of freedom and human rights. The alliance invited Macedonia to join and set up a readiness initiative that could quickly deploy troops, planes and ships in any crisis.

And every NATO member is increasing defense spending, something Trump has focused on pushing for.

None of that suggests that NATO is about to collapse despite Trump's antipathy.

This is not the first time the alliance's purpose has been questioned. After the Cold War, NATO was looking for a mission, and it found one in the Balkans and in Afghanistan, until Russia's resurgent threat underlined the need for a transatlantic security alliance.

Yet Trump is the most important leader in NATO, so putting his behavior down as just the rhetoric of an arbitrary disrupter isn't giving him his due. He is the person who would ultimately have to take the decision to react if there were any incursion by Russia into NATO territory.

Would he find it in America's interests to stand up to a provocation by Moscow, especially if it is against a NATO member he considers has not been paying its way? Any ambivalence about a NATO country's fate is critical, since the entire credibility of the grouping rests on the certainty that an attack on one is an attack on all.

How Trump would react if pushed in that capacity is unknown. But for now, he's made his feelings about the current state of the organization and the world's balance of power abundantly clear.

'What good is NATO'

Just before showing up on a mild summer evening in Brussels for an awkward photo-op with world leaders, Trump issued a tweet that explained everything.

"What good is NATO," the blast began, before lashing Germany and other allies that Trump accuses of leeching off American generosity and stinting on their own defense.

"Many countries are not paying what they should. And frankly, many countries owe us a tremendous amount of money for many years back, where they're delinquent, as far as I'm concerned," Trump had said in front of NATO Secretary-General Jens Stoltenberg earlier Wednesday.

One shocked senior European diplomat told CNN's Michelle Kosinski: "It's like the world gone crazy this morning. Trump's performance was beyond belief."

In apparently rejecting traditional US reverence for the transatlantic alliance, Trump is departing from the views of many senior members of his own administration and military establishment, 97 US senators who voted on Tuesday to support NATO in a pre-emptive swipe against him, and the other 28 members of the alliance.

Even House Speaker Paul Ryan, who is usually loath to criticize Trump, told reporters: "NATO is indispensable. It's as important today as it ever has been."

The White House, trying to put a strategic spin on what seems to be Trump's instinctive dislike of NATO, argues that he is actually trying to bolster the alliance with his demands for more defense spending.

"President Trump wants to see our allies share more of the burden and at a very minimum meet their already stated obligations," White House press secretary Sarah Sanders said. Another senior official said the President's attacks on Germany represented "tough medicine" for a crucial US ally that's well below the guideline of 2% of gross domestic product for member state spending on defense by 2024.

Trump is not the first president to complain that the US is not getting a fair shake, and his complaints can be easily justified. But the argument that he is acting out of an altruistic desire to make the alliance more effective might be more convincing if the President ever openly praised NATO.

He did not in his public appearances Wednesday invoke NATO's role in keeping Europe free and the Soviet Union at bay. Last year, he practically had to be forced by his staff to reinforce NATO's core Article 5 clause on collective defense. While he berates US partners for the debt they owe to the US, Trump rarely mentions that the only time Article 5 was invoked was to defend the US after the 9/11 attacks and doesn't often acknowledge the deaths of hundreds of soldiers from NATO nations in America's wars in Afghanistan and Iraq.

"It makes me think that the fundamental purpose of NATO either isn't understood or is being pushed aside," David Priess, a former CIA officer who is now a political commentator and author, said on CNN. "The first NATO secretary-general famously said that the purpose of NATO was to keep the Soviet Union out, the Americans in and the Germans down."

"The President seems to have corrupted that to be build the Russians up, get the Americans out and put the Germans down," Priess added.

There has certainly been no sign from the President that he subscribes to the philosophy of Harry Truman, the President instrumental in establishing the US-led post-World War II international order that Trump often seems to be trying to tear down.

"We shall not realize our objectives, however, unless we are willing to help free peoples to maintain their free institutions and their national integrity against aggressive movements that seek to impose upon them totalitarian regimes," Truman said in laying out his doctrine of US leadership in 1947.

Trump's hostility to Truman's principles horrified Burns.

"This is a radical revolution. It is hurting America," he said.

Taking aim at Germany

Trump's assault on Germany was particularly astonishing given that it was unprompted and erupted in what had been expected to be a routine breakfast photo-op with Stoltenberg.

He complained about the Nord Stream 2 pipeline, a Russian-owned project that Germany uses to buy gas from Moscow and that the Obama administration also worried was a national security liability and gave significant leverage to the Kremlin.

"So we protect you against Russia, but they're paying billions of dollars to Russia, and I think that's very inappropriate," Trump said, exaggerating the proportion of Germany's energy the pipeline supplies. "Germany is a captive of Russia," he said.

The comment was typical of the way that Trump sometimes states mainstream US opinion in such an explosive manner that it eviscerates diplomatic convention and erupts into huge controversies.

The President's antipathy for German Chancellor Angela Merkel, who has often been referred to as a guardian of Western values in the Trump era, is well known. He often berated her on the campaign trail, and her position as the most important leader in the European Union made her a personal target of his trade rhetoric, which has escalated into a tariff war.

But it is difficult to think of a more offensive personal insult to Merkel than Trump's captive jab. The German leader grew up behind the Iron Curtain in Soviet-dominated East Germany and made the building of a plural, democratic political system her life's work.

"I have witnessed this myself, that a part of Germany was controlled by the Soviet Union. And I am very happy that we are today unified in freedom as the Federal Republic of Germany," Merkel said, responding to Trump's attack later on Wednesday.

Trump's attack on the German leader -- perhaps motivated by her weakened political state back home, could be an attempt to insulate himself from criticism that he is under the influence of Putin before their summit -- bewildered his critics in the United States.

Former Secretary of State John Kerry said the criticism of Germany was "disgraceful" and "destructive." In a joint statement, top congressional Democrats Sen. Chuck Schumer of New York and Rep. Nancy Pelosi of California said it was "an "embarrassment."

"His behavior this morning is another profoundly disturbing signal that the President is more loyal to President Putin than to our NATO allies," they wrote.

"You can express yourself without trying to tear down an alliance that's been important to the security of Americans," he told CNN's Manu Raju.