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Six Things to Know About North Korea’s Newest Missile

North Korea’s latest technological breakthrough calls for better deterrence and better missile defense.
April 17, 2023
Six Things to Know About North Korea’s Newest Missile
A man walks past a television screen showing a news broadcast with file footage of a North Korean missile test, at a railway station in Seoul on April 13, 2023. - North Korea fired a ballistic missile on April 13, Seoul's military said, prompting Japan to briefly issue a seek shelter warning to residents of the northern Hokkaido region. (Photo by Jung Yeon-je / AFP) (Photo by JUNG YEON-JE/AFP via Getty Images)

North Korea successfully carried out its first-ever flight test of a Hwasong-18 solid-fuel intercontinental ballistic missile (ICBM) on April 13, which it called a “miraculous success” and an improvement on its ability to mount a quick “nuclear counterattack.” This recent test follows the test of a high-thrust, solid-fuel engine in December and the display of a new solid-fuel ICBM during a military parade in February.

What does the latest test mean both operationally for North Korea’s nuclear capabilities and for U.S. policy toward North Korea? How much more of a threat does North Korea pose now than it did before developing this technology? And how should the United States respond? Here are the six things to consider about North Korea’s newest missile.

1. Solid-fuel ICBMs are harder to detect and preempt.

Most of North Korea’s ballistic missiles use liquid fuel and require hours of fueling at the launch site prior to use. This was the technology used by the previous missiles North Korea tested, including the Hwasong-14, -15 and -17. Slow fueling processes make it easier for the United States and its allies to detect the launch and conceivably—if they are convinced North Korea is about to launch an attack—to preempt it, defend against it, or if necessary, retaliate. The new, solid-fuel Hwasong-18 does not require fueling prior to launch, which means it can be hidden more readily and employed much faster, dramatically reducing the time to detect a launch and respond during a crisis. A liquid-fueled ICBM needs to be employed within a short period after fueling, whereas the solid-fuel model is much more “shelf-stable” (to borrow a term from the grocery store). It can sit in storage or a hidden silo, fully ready to go, for extended periods of time. If solid-fuel missiles are deployed, North Korea will gain a potent new weapon with which to threaten the United States, South Korea and Japan—which it views as its three principal enemies.

2. The full capabilities of the North’s ICBMs remain unclear.

North Korea has test-fired many ballistic missiles of varying ranges, and clearly has the capacity to strike the continental United States. However, it’s not clear if it has mastered the steps necessary to top a rocket with a warhead that can withstand the harsh conditions of atmospheric reentry and accurately strike targets. The Hwasong-18 is a three-stage missile and the North has successfully tested the first two stages (boost phase and midcourse phase) in the waters off its east coast, but it has not yet tested the missile’s terminal phase. Thus, the North could still face difficulties in ensuring that the missile does not break apart prior to impact.

3. North Korea’s solid-fuel technology increases U.S. vulnerability to nuclear attack.

While the latest technical milestone of the solid-fuel ICBM may not be a game-changer, the test marks an important advance in North Korea’s goal to build a nuclear arsenal that could directly threaten the United States. What the testing of a solid-fuel technology further shows is that, over time, the country’s missiles have increased not just in quantity but also in sophistication and range. They now pose a credible threat to the continental United States despite the U.S. deployment of limited missile defense systems. A strike carried out with a relatively small number of solid-fuel ICBMs could overwhelm the U.S. Ground-based Midcourse Defense system, which has up to 64 missile interceptors capable of countering North Korean ICBMs deployed in Alaska and California. With the assumption that about four interceptors are required for a high probability of defending against each incoming missile, some 17 North Korean ICBMs could theoretically overwhelm the ground-based interceptors.

4. The solid-fuel ICBM is part of a growing North Korean threat amid an increasingly tense environment.

This test is in accordance with the five-year plan set forth in January 2021 at the Eighth Party Congress, where Pyongyang announced that it would develop not only solid-fuel ICBMs that could be launched from both land and sea but also tactical nuclear weapons, hypersonic missiles, nuclear-powered submarines, and spy satellites. North Korea has already tested an ICBM designed to carry multiple warheads; a solid-fuel rocket engine; tactical, nuclear-capable rockets; a sea-launched, nuclear-capable missile; and now a solid-fuel ICBM. After testing nearly 100 missiles in 2022—a record-breaking number—the North has fired around 30 missiles so far this year. Its next milestones are to develop reliable reentry vehicles and, after that, multiple reentry vehicles so that a single ICBM can carry multiple warheads (a technology that the United States mastered decades ago).

With large-scale U.S.-South Korea military exercises having recently concluded, regular U.S.-South Korean-Japanese exercises having just been announced, and a U.S.-South Korean summit just around the corner on April 26, the timing is ripe for a North Korean provocation designed to remind the world that it is a dangerous and disruptive force. Meanwhile, U.S.-North Korea relations are at a stalemate with little hope of any diplomatic breakthroughs. Following the failure of his high-level summits with then-President Trump, Kim Jong Un has ignored the Biden administration’s invitations to talk.

There appear to be few impediments preventing Pyongyang from proceeding down the path it as chosen. The United States and its allies can do little to stop North Korea’s missile testing campaign. Intensified U.S.-China competition and the war in Ukraine have only made the world increasingly more polarized, and North Korea is benefitting from closer cooperation with China and Russia. Both Moscow and Beijing are now unwilling to work with Washington to enforce sanctions on North Korea.

5. North Korea’s long-term goal is to undermine the U.S.-South Korea alliance.

Kim Jong Un, who reportedly oversaw the Hwasong-18 test alongside his wife and young daughter, said the test was meant to “make the enemies suffer from fear and extreme anxiety” and that the Hwasong-18 will “greatly reinforce the components of our strategic deterrent, rapidly increase the utility of the nuclear counterattack posture and innovate the practicality of the offensive military strategy.”

Over the long-term, however, North Korea’s main strategic goals remains undermining the U.S.-South Korea alliance. The Kim regime’s threats to launch a preemptive attack on Seoul in the past year suggests that it envisions a wider role for the its nuclear and missile arsenal beyond deterrence and self-defense. Using nuclear threats as a way to split the United States from South Korea is likely what Kim has in mind. He may calculate that, in the future, the United States will not be willing to “trade Seattle for Seoul” and will eventually withdraw its forces from South Korea, leaving the South vulnerable to his nuclear blackmail. In other words, by threatening the United States, Kim may be able to make it fold in its nuclear umbrella, leaving South Korea exposed.

6. The United States needs to boost its missile-defense and deterrence capabilities in response to the North Korean threat.

The first U.S. response to the growing North Korean threat should be a recommitment to missile defense. No one system offers a full-proof defense, so the United States needs to invest in both theater and homeland missile defense, employing systems that are both sea-based and land-based. It’s important to integrate the missile defense systems of the United States, South Korea, and Japan so that sensors can more reliably and quickly detect North Korean missile launches.

At the same time, the United States needs to bolster its extended deterrence capabilities to reassure South Korea and deter North Korea from employing its nuclear arsenal. This doesn’t require stationing U.S. tactical nuclear weapons in South Korea, as some South Koreans desire. (American nuclear weapons were withdrawn in 1991.) Tactical nuclear weapons on South Korean soil would be too vulnerable to a preemptive North Korea strike and their presence could prove destabilizing. Having South Korea develop and field its own nuclear weapons—a move supported by at least 70 percent of South Koreans in recent polls—could prove even more dangerous and destabilizing at this time.

Instead, the United States could enhance its deterrence by continually deploying either U.S. nuclear-capable submarines or aircraft around the Korean Peninsula. The Biden administration could also adopt a policy of “strategic ambiguity” to enhance deterrence by leaving the North Koreans guessing about which U.S. weapons systems are nuclear-armed. The Pentagon should also strengthen nuclear consultations with the South Korean military so that Korean leaders are confident that the U.S. nuclear umbrella will continue to protect them in a crisis.

North Korea’s test of a solid-fueled ICBM is just the latest in a nearly two-decade procession of technological advancements that together amount to a slow-motion nuclear crisis. It’s too late to prevent the North Koreans from developing a serious nuclear and missile program—they clearly already have it, and they have no inclination to give it up. The United States and its allies need to get ahead of the curve to prevent the situation from further deteriorating by strengthening their missile defenses and their deterrence of North Korea.

Sue Mi Terry

Sue Mi Terry is director of the Asia Program and the Hyundai Motor-Korea Foundation Center for Korean History and Public Policy at the Wilson Center. A former CIA analyst, she served on the National Intelligence Council from 2009 to 2010 and the National Security Council from 2008 to 2009.