On "Special Report" tonight, Charles Krauthammer said President Trump's first foreign trip as commander-in-chief got off to a strong start in the Middle East, but the second part of the trip in Europe was a "disaster."

He didn't take issue with Trump scolding our NATO allies and telling them to pay their "fair share" of the alliance's defense costs.

Instead, Krauthammer said, Trump left NATO members unsettled by not reiterating U.S. commitment to Article 5 of the NATO charter.

Article 5 is a mutual defense pledge and NATO's core tenet. It means that "an attack against one ally is considered as an attack against all."

"The world was waiting for Trump to say, 'I support Article 5,'" Krauthammer said. "That was the purpose of the visit, and he wouldn't say it."

He said that omission is going to have many lasting repercussions, weakening NATO unity over time.

"It's really hard to understand why he didn't say it," Krauthammer said. "The omission was a statement."

Watch more above.

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