(CNN) With his jaw set and his arms crossed, Donald Trump delivered the most incendiary public threat by an American president in many decades.

Trump, instantly escalating a nuclear showdown with North Korea, warned that if the isolated state did not quit making its own threats, it would face "fire and fury like the world has never seen."

From political, diplomatic, and historical perspectives, Trump's threat, delivered from his golf club in New Jersey, was an extraordinary moment and shattered years of national security conventions in apparently threatening to use nuclear weapons in response to an adversary's rhetoric -- rather than an existential threat to US security.

It might have also walked the United States closer to a full on showdown with North Korea, and placed his own personal reputation on the line in a test of wills with Kim Jong Un.

"He has been very threatening beyond a normal state. They will be met with fire, fury and frankly power the likes of which this world has never seen before," said Trump in remarks that seemed more typical of the blasts of rhetoric issued by the North Korean news agency KCNA rather than of a US president.

By accident or design, Trump established a red line -- an apparent contravention of efforts by his Secretary of State Rex Tillerson and Secretary of Defense James Mattis to tone down tensions with Pyongyang.

By making such an explicit threat to North Korea, on camera, the President also invested his own personal prestige into the center of the crisis. The next time Kim makes some kind of threat to the US or its allies, Trump will immediately come under pressure to make North Korea pay a price -- or risk having his authority exposed as hollow.

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The comments also came at a time when the President is undergoing a crisis of the kind of credibility commanders-in-chief need during a major national security crisis.

A CNN poll Tuesday said that nearly three-quarters of Americans did not trust what is coming out of the White House. And a CBS News poll released Tuesday showed that 61% of Americans were uneasy about Trump's ability to handle the situation with North Korea.

"Donald Trump may put himself in a box because he is promising action that he might actually be unwilling to deliver on," said Timothy Naftali, a presidential historian at New York University. "So he should be careful what he threatens because he may, for the sake of US credibility, have to act on his threats. That's why presidents are so careful not to bluff. The other side can call your bluff."

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Playing into North Korea's hands?

The revelation Tuesday, first published by The Washington Post, that North Korea had succeeded in miniaturizing a nuclear warhead to insert on an inter-continental ballistic missile appeared to take Pyongyang across an important threshold in its race to deploy nuclear weapons, and to narrow the window Trump faces in deciding how to respond to a new threat to the American homeland.

Given the position of power and influence the United States wields, its presidents have tended to weigh their words carefully, typically thinking several moves ahead. The human carnage that could result from any North Korean attack on South Korea in response to US military action has also given US leaders pause.

Trump's broadside on Tuesday sparked warnings that he was pouring fire on an already volatile situation, and could be playing into Pyongyang's hands by validating its narrative that the US wants to go to war with North Korea -- a rallying point for the regime.

"It is acceptable for the President to say 'here's what we are going to do and here are the steps we are going to take ... and we are going to respond .... appropriately and with strength,'" Jamie Metzl, a senior fellow at the Atlantic Council, told CNN's Jake Tapper.

"Just to throw around macho words or fake macho words, I don't know what that gets us," Metzl added.

Republican Sen. John McCain, the chairman of the Senate Armed Services Committee, faulted Trump's gambit.

"I take exception to the President's comments because you've got to be sure that you can do what you say you're going to do. In other words, the old walk softly but carry a big stick," McCain told KTAR radio in Arizona.

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Looking for motive behind Trump's words

It was not immediately clear whether Trump's comments were off the cuff, or the product of a deliberate process between the President, senior members of his national security team and top military brass.

But the ferocity of his rhetoric has few recent precedents. President Ronald Reagan raised eyebrows by calling the Soviet Union an "Evil Empire" but not in the context of a threat. President George W. Bush once said "bring 'em on," when referring to the possibility that insurgents could use military force to push US forces out of Iraq, a comment for which he later expressed regret.

Bush, who liked to show some swagger in his first term, also put North Korea in an "axis of evil."

Other presidents have surprised their teams by making policy on the hoof, Naftali said, including Richard Nixon who declared publicly in 1973 that the US would not give into blackmail from terrorists.

The closest parallel might be President Harry Truman's warning to Japan after the atomic bomb attack on Hiroshima and before the strike on Nagasaki, that if Japan did not immediately surrender it would face "a rain of ruin from the air, the like of which has never been seen on this Earth."

But the circumstances of that warning -- at the end of the most ruinous conflict in human history -- hardly compare to the suddenness of Trump's public, televised warning on Tuesday.