President Trump’s warning on Tuesday that North Korea would experience “fire and fury like the world has never seen” if it continued threatening the United States was a remarkable escalation of military rhetoric with little precedent in the modern era, historians and analysts said.

Mr. Trump’s menacing remarks echoed the tone and cadence of President Harry S. Truman, who, in a 1945 address announcing that the United States had dropped a nuclear bomb on Hiroshima, urged the Japanese to surrender, warning that if they did not, “they may expect a rain of ruin from the air, the like of which has never been seen on this earth.”

It is not clear whether Mr. Trump intended the historical parallel — White House officials did not respond to questions about how much planning went into his brief statement, or what was intended by the alliterative language — but it was a stark break with decades of more measured presidential responses to brewing foreign conflicts.

“It’s hard to think of a president using more extreme language during crisis like this before,” said Michael Beschloss, a presidential historian. “Presidents usually try to use language that is even more moderate than what they may be feeling in private, because they’ve always been worried that their language might escalate a crisis.”