party congress in January, Mr. Kim doubled down on his nuclear arms buildup, offering a laundry list of weapons he said he planned to develop. They included “multi-warhead” nuclear missiles, “hypersonic” missiles, land- and submarine-launched I.C.B.M.s that use solid fuel, and “ultramodern tactical nuclear weapons.”

Whether North Korea has mastered the technology needed to send an intercontinental nuclear warhead into space and then guide it back through the earth’s atmosphere to its target is still unclear. North Korea has yet to demonstrate that its warhead can survive the intense heat and friction created by re-entry.

When North Korea resumed missile tests in 2019 following the collapse of the Kim-Trump talks, the tests featured three new weapons, code-named KN-23, KN-24 and KN-25 by outside experts.

They each marked big advances in North Korea’s short-range ballistic missile program.

Unlike its older missiles that used liquid fuel, all three of the new missiles used solid fuel. The new solid-fuel weapons, mounted on mobile launchers, are easier to transport and hide and take less time to prepare. And at least two of them, KN-23 and KN-24, could perform low-altitude maneuvers, making them harder to intercept.

At a military parade earlier this year, North Korea displayed what looked like a bigger, upgraded version of KN-23. Photos released by the North Korean media indicate that was the weapon tested on Thursday.

The new missile was developed to be larger than KN-23 in order to carry a bigger warhead and more fuel.

Pukguksong submarine-launched ballistic missiles since 2015.

During the military parades held in October and earlier this year, North Korea displayed what looked like two upgraded versions of its Pukguksong submarine-launched ballistic missiles. The country currently has only one submarine that can launch a ballistic missile, but says it is building a new one with greater capabilities.

North Korea has one of the largest standing armies in the world, with more than one million soldiers. But much of its equipment is old and obsolete, and the military lacks fuel and spare parts.

North Korea has sought to make up for its shortcomings by building nuclear weapons.

Mr. Kim justifies his family’s dynastic rule of North Korea by saying that the nuclear arsenal his government has built was a “treasure sword” keeping North Koreans safe from foreign invasion. He tells his people that they are under the constant threat of an American attack.

At the January party congress, Mr. Kim said that his weapons program “never precludes diplomacy” but “guarantees its success.” He has also said he no longer holds any expectations for dialogue unless Washington makes an offer that satisfies his government.

The test this week reflected Mr. Kim’s determination, analysts said.

It showed that “North Korea was pushing ahead with the plans” set down by Mr. Kim during the party meeting, said Kim Dong-yub, a professor at the University of North Korean Studies in Seoul. “As it had stated before, North Korea had no intention of moving first to offer a concession or make a proposal.”

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