“I hear fear in their voice,” said Shin Won-sik, a three-star general who was the South Korean military’s top operational strategist before he retired in 2015. “They can’t fight a war with the Americans when their fighter jets don’t even fly far because of lack of fuel and fear of crashing.”
Even as the North has matched Mr. Trump’s recent bellicose rhetoric, its military has warned units on the border with South Korea against rash decisions and reminded them to report up the chain of command before taking any action, according to South Korean intelligence officials who briefed lawmakers on Tuesday.
“They are careful to avoid an accidental provocation or clash,” Lee Cheol-woo, chairman of the South Korean Parliament’s intelligence committee, quoted officials as saying during the closed-door session.
The extreme rhetoric on both sides and the unconventional nature of both leaders are widely seen as volatile elements in the current standoff between North Korea and the United States over Pyongyang’s nuclear weapons program. Many people fear that Mr. Kim or Mr. Trump might be impulsive enough to start a conflict even if their advisers warn them against it.
But while some longtime observers of North Korea agreed that the situation was fraught with uncertainty, they said it would be wise not to overreact to Pyongyang’s aggressive statements.
“They may have the will but not the means to fight the Americans,” said Shin In-kyun, a military expert who runs the Korea Defense Network, a civic group.
The threat to shoot down a United States bomber is a case in point. North Korea last shot down an American warplane in 1969, killing all 31 members of the crew of a spy plane that was flying off its coast. In 1994, it shot down a United States Army helicopter that accidentally crossed into its airspace.
But today, military analysts said, it would be all but impossible for North Korea to shoot down American warplanes like B-1B strategic bombers, F-15 fighter jets or F-35 stealth fighters, especially if they were flying in international airspace well off the North’s coasts.
North Korea’s SA-5 land-to-air missiles have a range of only 155 miles, they said. American warplanes operate under the protection of radar-jamming technology, and North Korea’s aging MiG fighter jets, which are often grounded for lack of fuel and parts, are no match for them, Mr. Shin and other analysts said.
Much as Mr. Trump’s aggressive rhetoric about North Korea — like his threat at the United Nations to “totally destroy” the country — appeals to his core supporters, Mr. Kim needs to demonstrate to his people that he is not backing down from foreign threats, analysts said.
But they noted that the North tends to couch its threats, however lurid, with carefully worded conditions.
When North Korea threatened in August to create an “enveloping fire” around the American territory of Guam with ballistic missiles, its original statement said only that it was “seriously examining” such a plan. Responding on Friday to Mr. Trump’s United Nations speech, Mr. Kim called him a “mentally deranged U.S. dotard.” But he did not commit to a course of action, saying only that he would “consider” the “highest level of hard-line countermeasure in history.”
And Mr. Ri, the foreign minister, did not say Monday that North Korea would shoot down American bombers, only that it had “the right” to do so.
“The North Koreans know how to choose their words,” said Cheon Seong-whun, a visiting research fellow at the Asan Institute for Policy Studies in Seoul, who served as a presidential secretary for security strategy in South Korea until early this year. “They know how to calculate their stakes. They are not reckless.”
With its threats, North Korea is trying to make the United States think twice about further shows of force, even as it seeks to portray itself as playing defense against an American bully, said Lee Sung-yoon, a Korea expert at the Fletcher School of Law and Diplomacy at Tufts University.
At the same time, Pyongyang probably hopes China and South Korea will call for calm and restraint, while using Mr. Trump’s threats as justification to conduct another missile or nuclear test, Mr. Lee said.
“North Korea has to sound tough because it fears that if it is pushed back under American pressure now, it will never regain its ground,” said Kim Yong-hyun, a professor of North Korean studies at Dongguk University in Seoul. “It fears that if it backs down, China and Russia won’t come to its aid.”
Analysts said the lack of a regular, high-level diplomatic contact between Pyongyang and Washington made it likelier that one side would misread the other’s intentions, rendering the recent bombastic rhetoric all the more dangerous.
“The level of mutual understanding between the United States and North Korea is low, while the chances of miscalculation are high,” Mr. Cheon said.
Lu Kang, a spokesman for the Chinese Ministry of Foreign Affairs, said on Tuesday at a regular news conference in Beijing that China was “very displeased with the escalating war of words between the United States and North Korea,” adding that there would be “no winners from rashly triggering war on the peninsula.”