Kim Jong Un is modernizing his arsenal of nuclear weapons and missile systems. Nuclear modernization includes, at a minimum, activities maintaining secure and reliable nuclear forces; though more importantly, it refers to activities improving quantitative and qualitative aspects of nuclear forces. North Korea is modernizing in terms of increasing fissile material production capacities and stockpiles, boosting the diversity of its missile capabilities, and developing a new ICBM. Its testing spree is primarily aimed at technical progress, not political signaling towards Seoul or Washington. Pyongyang continues its nuclear modernization despite economic hardships and total isolation, using the momentum of South Korea, the U.S., and allies being preoccupied with pressing domestic and international affairs. Nevertheless, allies need to keep North Korea among their top priorities, finding new pathways to effectively manage if not contain the threats posed to regional security. Estimates vary, but analysts assume that North Korea has stockpiled enough fissile material to build between 20 and 60 nuclear warheads. Pyongyang itself showcased two different warhead designs in 2016 and in 2017. The different yields of its six nuclear explosive tests suggest that it is able to build simple fusion bombs and boosted-fission—if not thermonuclear—bombs. In January 2021, at the Party Congress, Kim Jong Un announced that North Korea will develop tactical nuclear weapons with smaller yields, in addition to strategic warheads with higher nuclear yields. Satellite imagery of nuclear installations provides clues about the current state of Pyongyang’s nuclear program. Over the course of 2021, three observations stood out: North Korea continued production of uranium concentrate at Pyongsan, restarted the five-megawatt electrical reactor at Yongbyon presumably to produce plutonium and tritium, and expanded its uranium enrichment facility at Yongbyon to increase its capacities. In March 2022, South Korean government sources reported activities at Punggye-ri, potentially the restoration of testing tunnels at North Korea’s only nuclear test site. With regard to missile technologies, Pyongyang appears to be making significant qualitative progress, but not in game-changing strides. Its test-events in September 2021, as well as between January and March 2022, gradually accomplish the weapons technologies goals outlined by Kim Jong Un in January 2021. These developments aim to increase the survivability of North Korea’s arsenal by diversifying its nuclear forces, as well as seeking to bolster Pyongyang’s deterrence by facilitating a posture of directly threatening the U.S., in addition to cementing the threat of regional nuclear escalation. Most recently, North Korea conducted four test-events that contribute to its intercontinental ballistic missiles (ICBM) program. Pyongyang’s state media framed the first two as “satellite subsystem” tests to “confirm[…] the characteristics of the high-resolution camera system… and altitude control devices.” The U.S. and open-source analysts later argued, however, that North Korea had tested components of an ICBM, presumably for the Hwasong-17, an ICBM showcased at the 2020 military parade and 2021 defense exposition. The Hwasong-17 is particularly significant as it might be able to deliver multiple re-entry vehicles over intercontinental ranges. North Korean state media outlets did not carry any information about the third test-event, but other sources noted a failed launch. Pyongyang then celebrated the fourth test-event as the first successful test-firing of the Hwasong-17. However, based on satellite imagery, open-source analysts argue that the third test-event was a failed launch of the Hwasong-17, while the fourth test-event was a launch of the Hwasong-15, the ICBM once tested in November 2017. If one thing is clear, however, it is North Korea’s determination to pose a direct threat to the U.S. Pyongyang is keen to have the capability to deliver nuclear warheads to the U.S. mainland, ideally using multiple independently targetable re-entry vehicles that challenge missile defense systems. Kim Jong Un also affirmed the ambition to build solid-fueled ICBMs that might facilitate rapid deployment. Respective engine tests—as well as the development and launch of satellites for military reconnaissance—might be some of the next events to take place. Prior to the ICBM-related test-events, North Korea conducted a testing spree, with five test-events in September and seven in January. These test-events confirm that Pyongyang is eager to make headway with 1.) building technologies that challenge missile defense systems, 2.) developing a sea-based nuclear deterrent, and 3.) having a diverse arsenal of short-range delivery systems. North Korea conducted two tests of maneuverable re-entry vehicles delivered by a medium-range ballistic missile—a shortened version of Hwasong-8—in early January 2022, although its state media reported these as tests of hypersonic missiles. Pyongyang did indeed test-launch a hypersonic glide vehicle on the medium-range ballistic missile, Hwasong-8, in September 2021. These technologies are not game changers but might provide North Korea the heightened ability to challenge theatre missile defense systems more efficiently than by employing multiple ballistic missiles to swamp defense systems. Pyongyang’s quest to build sea-launched ballistic missiles (SLBM) has been more successful than its efforts to build submarines to launch from. North Korea has developed three types of SLBMs, testing the Pukguksong-1 between 2015-2016, the Pukguksong-3 in 2019, and Pukguksong-5 in September 2021, each from undersea platforms. In January 2021, Kim Jong Un named nuclear-powered submarines, presumably capable of launching SLBMs, as one of five priorities for defense developments. While this might not be immediately achievable, North Korea aims to have a nuclear dyad—instead of a solely ground-launched nuclear monad—to increase the survivability of its nuclear forces. The greatest diversity exists in the category of short- to theatre-range strike capabilities. In both September 2021 and January 2022, North Korea tested long-range cruise missiles as well as the short-range ballistic missile KN-23 launched from railcars, among other systems. Most of Pyongyang’s tests since 2019 involved the short-ranged ballistic missile systems KN-23 and KN-24, as well as the KN-25, which are solid-fueled, mobile-based, and capable of multiple launches. This category of systems affirms a deterrence strategy of “asymmetric escalation” to threaten early use of nuclear weapons within the region. It is notable that Kim Jong Un has not been present for most test-events, particularly not for short-range ballistic missile testing. On the one hand, Pyongyang’s official reporting might aim to “normalize” these missile tests, framing them as routine exercises to improve operability and ensure combat readiness. On the other hand, state media framing of these test-events as taking place on short notice might aim to suggest North Korea’s ability to employ short-range missile systems in contingencies, even without the supreme leader’s authorization and presence. Despite economic hardships and self-imposed, pandemic-related total isolation, Pyongyang continues developing and modernizing its nuclear weapons program by expanding its capacity to produce fissile materials and grow its materials stockpile, as well as boosting the diversity of its short- to theatre-range delivery systems, and pursuing its newest ICBM. These activities pose threats to regional security and beyond, challenging South Korea, the U.S., and allies to square the circle of containing threats, boost deterrence, and leave diplomatic off-ramps for the North Korean regime. But for now, South Korea will focus on ensuring national security during this presidential transition period and initiating new policies while U.S. mid-term elections set other priorities and international affairs keep allies preoccupied. The momentum of flying below the political radar and moving its nuclear modernization forward remains on Pyongyang’s side. Table: List of recent test-events by North Korea What was tested?When?Long-range ballistic missile (Hwasong-15 rather than 17?) March 24, 2022Long-range missile components (for the Hwasong-17?), “satellite subsystem development tests”, “attitude control device” February 27, 2022, and March 5 (and March 16?), 2022Intermediate-range ballistic missile (Hwasong-12) January 30, 2022Long-range cruise missile, land-attack January 25, 2022, also September 11-12, 2021 Short-range ballistic missile systems, solid-fueled & road-mobile & rail-mobile (KN-23, KN-24) January 14, January 17, and January 27, 2022, also 2019-2021 Maneuverable re-entry vehicle, delivered by medium-range ballistic missile (shortened Hwasong-8) January 5 and January 11, 2022Hypersonic boost glide vehicle, delivered by medium-range ballistic missile (Hwasong-8) September 28, 2021 Sea-launched ballistic missile, medium-range (Pukguksong-5) September 30, 2021Source: author’s own table. Acknowledgment: This commentary is based on input delivered to the Northeast Asia Security Symposium organized by Young Professionals in Foreign Policy (YPFP) Tokyo on 28 March 2022. The author would like to thank Julian Gluck, Byron Muhlenberg, and Lauren Power for the opportunity to discuss North Korea’s nuclear modernization.