Here's how Donald Trump took shots at NATO in 2018 - and it spurred Jim Mattis to quit in protest

"All this bluster and blasting."

US-NATO ties got off to a rocky start in 2018, when reports emerged in the first days of the year of Trump's contentious dealings with alliance partners at a summit in May 2017.

Trump had given a speech that was criticized widely for appearing to undercut the Article 5 collective-defense provision that undergirds NATO.

According to a Politico report in January, he left diplomats from the European Union dumbstruck after a meeting that same day.

"He was very tough and very outspoken in his intervention," said a European diplomat who was present. Trump's comments at the dinner were "unlike anything they’ve ever heard" in such a setting, another European said. "All this bluster and blasting. He walks in and starts talking, breaking china all over the place."

"Few allies want that."

Defense Secretary Jim Mattis is seen as a stalwart supporter of NATO, but even he has been at odds with the defense alliance.

In January, he sent a letter to NATO headquarters calling for a formal NATO mission to Iraq with a semi-permanent or permanent command to train Iraqi forces, senior NATO diplomats told Reuters.

While NATO had some trainers in Iraq at the time, there were less than 20 of them, and the alliance was wary of the request.

"The United States is pushing hard for a NATO role in Iraq, not in a combat role, but for a long-term assignment," a senior NATO diplomat told Reuters.

"This looks suspiciously like another Afghanistan," where NATO is funding and training Afghan forces, the diplomat added. "Few allies want that."

Just a joke.

According to a late-June report by The Washington Post, Trump poked fun at the ongoing tension between the US and the rest of NATO during a March meeting with Sweden's prime minister.

The US is far and away NATO's largest member. After the prime minister explained to Trump that his country was not a NATO member but worked closely with the alliance, Trump reportedly responded by saying that was the kind of relationship with NATO that the US should consider.

A senior administration official told The Post that the remark was a joke.

"There is growing frustration."

This summer, Trump took a more direct tack with his relentless criticism of NATO members' defense spending.

In June, Trump sent letters to other NATO countries, including Germany, Belgium, Norway and Canada, criticizing them for not spending enough on their defense and warning them that the US was losing patience with what it perceived as their failure to meet their obligations.

"As we discussed during your visit in April, there is growing frustration in the United States that some allies have not stepped up as promised," Trump wrote to German Chancellor Angela Merkel in what someone who saw it told The New York Times was a particularly pointed letter.

"Norway ... remains the only NATO ally sharing a border with Russia that lacks a credible plan to spend 2 percent of its gross domestic product on defense," Trump said in a June 19 letter to Norwegian Prime Minister Erna Solberg.

"Who would think!"

Trump traveled to Europe in early July for meetings with NATO leaders and with Russian President Vladimir Putin.

The US president again took aim at the alliance as he embarked on the trip.

"Getting ready to leave for Europe," Trump tweeted in the early morning hours on July 10. "First meeting - NATO. The U.S. is spending many times more than any other country in order to protect them. Not fair to the U.S. taxpayer. On top of that we lose $151 Billion on Trade with the European Union. Charge us big Tariffs (& Barriers)!"

As he departed the White House, Trump again slighted the US's alliance partners.

"So I have NATO, I have the UK which is in somewhat turmoil, and I have Putin," Trump told reporters on the South Lawn of the White House. "Frankly, Putin may be the easiest of them all. Who would think! Who would think. But the UK certainly has a lot of things going on."

"NATO has not treated us fairly but I think we'll work something out," Trump added. "We pay far too much and they pay far too little."

"Germany is totally controlled by Russia."

Trump kept up the broadsides in his opening remarks in Brussels, blasting Germany for its energy dealings with Russia.

"It's very sad when Germany makes a massive oil and gas deal with Russia where we're supposed to be guarding against Russia, and Germany goes out and pays billions and billions of dollars a year from Russia," Trump said at a working breakfast at the beginning of the summit.

"Germany is totally controlled by Russia," he added. "Because they're getting between 60 to 70% of their energy from Russia and a new pipeline."

Trump appeared to be referring to Nord Stream 2, a pipeline project backed by Merkel that will allow for more consumption of Russian energy. Official data showed that 35.3% of Germany's oil and gas imports come from Russia, according to Reuters.

"You tell me if that's appropriate," Trump said, "because I think it's not, and I think it's very bad thing for NATO."

"Angela, you need to do something about this."

Things only got more heated at the summit.

Trump singled out Germany for failing to meet the agreed-upon goal of spending 2% of GDP on defense. (NATO members agreed in 2014 to reach that level by 2024.)

"Angela, you need to do something about this," Trump said, using the German leader's first name in a breech of diplomatic protocol that prompted an emergency meeting of the alliance's leaders.

"The language was much tougher today," a source told Reuters. "His harshest words were directed at Germany, including by calling her Angela — 'You, Angela.'"

After the meeting Trump told the press that NATO leaders had agreed to consider his demand that they raise their defense spending to 4% of GDP, which drew an immediate rebuttal from French President Emmanuel Macron.

Trump did affirm his commitment to the alliance, but as he left the summit, he interrupted the Chancellor while she was addressing her fellow NATO leaders.

Trump kissed her and said, "I love this woman," adding, "Isn’t she great?"

"It’s up to psychologists and historians what to make of that," a senior German diplomat said of the interaction.

"I had an even better meeting with Vladimir Putin."

After the NATO summit, Trump traveled to Helsinki, where he met one-on-one with Russian President Vladimir Putin and appeared to side with Moscow over the issue of Russian interference in the 2016 presidential election and offered another slight to NATO.

"While I had a great meeting with NATO, raising vast amounts of money, I had an even better meeting with Vladimir Putin of Russia," Trump wrote. "Sadly, it is not being reported that way — the Fake News is going Crazy!"

"Congratulations, you're in World War III."

Trump spurned the alliance again after the trip to Europe, when he appeared to call into question the principal of collective defense on which NATO is based.

"Let's say Montenegro, which joined last year ... why should my son go to Montenegro to defend it from attack?" Fox News host Tucker Carlson asked Trump in an interview.

"I understand what you're saying — I've asked the same question," Trump said. "Montenegro is a tiny country with very strong people."

Carlson hastened to add that any country could have been included in his scenario. But Trump went on, suggesting Montenegro's "aggressive people" could spark a global conflict.

"By the way, they're very strong people — they're very aggressive people," Trump said. "They may get aggressive, and congratulations, you're in World War III."

Montenegro, NATO's newest member, spoke out in its own defense, and other experts pointed out that while there were good reasons to criticize NATO's recent expansion, the way in which Trump was doing it caused more harm than good, as it could signal an adversary like Russia that NATO powers wouldn't rush to the defense of a much smaller country.

John Bolton steps in.

In August, it was reported that, in an effort to avoid a blowup at the NATO summit in July, Trump's advisers, led by National Security Advisor John Bolton, pushed to have the formal agreement that is negotiated during the summit finished before the US president even left for the July 11 meeting.

NATO Secretary General Jens Stoltenberg backed the plan, telling ambassadors on July 4 that the usual wrangling over the agreement — renamed as a directive rather than a communique for this summit — had to be avoided.

NATO communiques usually take months to draft, with talks often coming down to the wire, as countries use the deadline as leverage to advance issues important to them. This year, Trump was only presented with a broad overview of the directive and not the details of the document, which stretched 79 paragraphs over 23 pages.

"We pay for LARGE portions of other countries military protection."

Just six days after the US midterm elections, and only hours after a display of unity by world leaders commemorating the 100th anniversary of the end of World War I, Trump launched a new broadside against NATO without naming the transatlantic alliance.

"Just returned from France where much was accomplished in my meetings with World Leaders. Never easy bringing up the fact that the U.S. must be treated fairly, which it hasn’t, on both Military and Trade," Trump said.

"We pay for LARGE portions of other countries military protection," he added, "for the great privilege of losing hundreds of billions of dollars with these same countries on trade. I told them that this situation cannot continue - It is, and always has been, ridiculously unfair to the United States."

"It is time that these very rich countries either pay the United States for its great military protection, or protect themselves," he said.

"It's a tale of two cities."

While Trump's dealings with NATO have been contentious, in terms of policy he has continued many of the efforts of his predecessor.

In that regard, "it's a tale of two cities," Jim Townsend, who was deputy assistant secretary of defense for European and NATO policy during the Obama administration, told Business Insider.

Trump has, on one hand, continued efforts to increase US forces in Europe and increase NATO's overall readiness. Even "coming down hard on the allies on the 2%" of GDP defense-spending level was carried over from the Obama administration, said Townsend, who is now an adjunct senior fellow in the Center for a New American Security.

"What was new of course was the rhetoric," he added.

The Trump administration's challenging of international cooperation and international institutions was a departure, "showing that this administration doesn't look on those institutions and that world order ... the way we have since World War II," Townsend said.

"There is no question about it."

Not all of NATO had been taken aback by Trump's approach. Countries on the alliance's eastern flank, where Russia's influence looms large, have welcomed a more assertive posture.

After the July summit, Polish President Andrzej Duda downplayed the severity of divisions between Trump and other NATO members and said debates over NATO spending that Trump had ignited were beneficial for countries like his because they had led to more defense spending by allies.

In his remarks, Duda mostly praised Trump's approach, and he insisted, despite an impression otherwise, that the rancorous discussions "undoubtedly confirm the North Atlantic Alliance's unity — there is no question about it."

"It's already penetrated the subconscious."

There have been divides among European governments in the way that they relate to Trump; divides that reflect how some newer allies approach governance, Townsend said — "a more populist, a more autocratic view of democracy and how they are going to govern."

Those "splits would've been there regardless of Trump," he said, adding that for other countries, doubts about the Trump administration's commitment to the alliance are lingering.

In Germany, where Chancellor Angela Merkel has been a particular target for Trump, the US president has already made a lasting impact.

"It's like your parents questioning their love for you," Norbert Röttgen, the chairman of the German federal parliament's foreign-affairs committee, told The New Yorker this summer. "It's already penetrated the subconscious."