SHANNON, Ireland — Halfway through a summer set of four international trips, President Donald Trump has proven himself to be an impolitic guest, soaking up pomp and pageantry while leaving behind hosts he scorched despite their best efforts to favor the president with flattery.

Trump on Friday wrapped up five days in Europe that, much like his stay in Japan two weeks earlier, showed how his “America First” foreign policy mixed with his “Me First” Twitter habit have made him an unpredictable partner for America’s allies, who continue to grapple with how to manage the president and fortify economic and strategic ties with the United States.

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Time after time, diplomatic niceties fell by the wayside as the president contradicted and undermined his hosts.

“Not only has Trump been ungracious on these trips, he is losing credibility with his behavior,” said presidential historian Douglas Brinkley. “No world leader can trust President Trump because at any moment he may shatter the glass right in front of him; a single whim, or tweet, could upend a deal that had been months in the making. He leaves world leaders wiping their brows and wishing for him to leave.”

The United Kingdom this week welcomed Trump for a grand state visit, an honor bestowed on only two previous presidents, hoping to strengthen ties and lay the groundwork for a new U.S.-U.K. trade deal as Britain moves toward exiting the European Union. But even as Trump praised the royal family (claiming “automatic chemistry” with Queen Elizabeth II), he meddled in the U.K.’s internal politics, played tough on trade and took a sharp jab at the American-born Duchess of Sussex, Meghan Markle.

At Trump’s next stop, Ireland’s leader had hoped for a grand welcome ceremony that would highlight ancestral ties with the U.S. He had to settle for a meeting with Trump in an airport lounge and a disagreement over the future of his nation’s border with Northern Ireland.

In France, where Trump attended a moving D-Day anniversary commemoration with other world leaders, President Emmanuel Macron stressed the importance of historic alliances while publicly papering over his disagreements with Trump over Iran. But with the gravestones of Normandy as a cringe-inducing backdrop, Trump sat for a Fox News interview in which he veered into a sharp dissection of domestic politics, harshly criticizing House Speaker Nancy Pelosi and special counsel Robert Mueller.

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It was the same story last month, when Japanese Prime Minister Shinzo Abe crafted a made-for-Trump itinerary in Tokyo that featured golf, American beef and Sumo wrestling. At a closing joint press conference, Abe stood by as the president publicly broke with Japan’s plan for managing the missile threat posed by North Korea.

While these last two foreign trips were largely designed to honor Trump, the next two are built around international summits in Japan and France where he won’t be the only object of attention. The Group of 20 summit in Osaka later this month will be particularly consequential: Trump will meet with Chinese President Xi Jinping in the midst of a trade war and he’ll hold his first face-to-face encounter with Russia’s Vladimir Putin since a Helsinki summit last summer where Trump rattled European capitals by publicly siding with Putin over his own intelligence agencies.

There were certainly moments of clear success for Trump this week in Europe.

The pageantry of the British state visit was impressive, complete with an opulent dinner at Buckingham Palace. Trump was gracious to the queen and stressed the “very special relationship” between the two nations. In a pair of ceremonies to mark the 75th anniversary of D-Day — one in Portsmouth, England, the other in Normandy — Trump hit the right notes as he praised the heroism of the American soldiers who fought on Omaha Beach.

“No world leader can trust President Trump because at any moment … a single whim, or tweet, could upend a deal that had been months in the making. He leaves world leaders wiping their brows and wishing for him to leave.” – Douglas Brinkley, presidential historian

The White House was thrilled with the trip. The potent images of a commander in chief on the world stage will serve as reminders of the powers of incumbency heading into a fierce re-election fight, Trump allies believe.

“With Democrats back home stalling his agenda with investigations, it’s important for the president to lead where he has authority, and that’s the international stage,” said Jason Miller, who served as communications director for the president’s 2016 campaign. “He is working on trade agreements, improving our stature when it comes to security on the global stage and helping our allies. The visuals this week are fantastic.”

But while public events went smoothly, Trump still at times baffled his allies — and undercut his own triumphs — with incendiary statements both in public and on his phone.

Before Air Force One even touched down in London, Trump had attacked the city’s mayor, accused Markle of being “nasty” and praised conservative leaders Boris Johnson and Nigel Farage as the United Kingdom prepares to replace Prime Minister Theresa May over her failure to secure a Brexit deal. Trump further rattled Britons by saying that “everything”— including the National Health Service — would be “on the table” in future trade negotiations. He later backed away from that idea.

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And amid the pageantry of his state visit in London, Trump’s mind was often elsewhere. In one memorable 1 a.m. Twitter burst, he went after both Senate Minority Leader Chuck Schumer and, improbably, Bette Midler. While Miller played down the moment, saying “there is not a single American voter who hasn’t already decided where they stand” on Trump’s Twitter feed, the tweets detracted from the somber D-Day ceremony later in the day.

In Brinkley’s view, “These trips should allow him to look like a true statesman but instead he steals the scene in his own crass way.”

Freking reported from London.