North Korea declared a no-first-use policy following its fourth nuclear test in 2016; however, it diluted its statement with the caveat that it would not “be the first to use nuclear weapons […] as long as the hostile forces for aggression do not encroach upon its sovereignty” (Korean Central News Agency 2016). Subsequent statements have also included such caveats; during the 75th anniversary of the ruling Korean Workers’ Party in October 2020, Kim Jong Un stated that North Korea’s nuclear deterrent “will never be used preemptively. But if, and if [sic], any forces infringe upon the security of our state and attempt to have recourse to military force against us, I will enlist all our most powerful offensive strength in advance to punish them” (38 North 2020).

At various times, North Korean media has also threatened to launch nuclear weapons in response to more minor provocations, such as joint US-South Korean military exercises (Ellyatt 2016). However, despite these occasional inflammatory statements, it is highly likely that North Korea—as with other nuclear-armed states––would only use its nuclear weapons in extreme circumstances, particularly if the continued existence of the North Korean state and its political leadership were in jeopardy.

Since 2010, North Korea has also been in the process of constructing an experimental light water reactor and in recent years has begun transferring major reactor components into the facility at Yongbyon. In 2019 and 2020, the IAEA reported that North Korea may have conducted infrastructure tests of the experimental light water reactor’s cooling system. Although this reactor appears to be designed for civilian electricity production, it would also have a latent capacity to produce weapons-grade plutonium or tritium that could be used for North Korea’s nuclear weapons program.

In May 2018, for example, a Washington Post article first reported the existence of a potential covert uranium enrichment site at Kangson––just outside of Pyongyang––citing work by the Institute for Science and International Security (Warrick and Mekhennet 2018). In July 2018, a team of researchers from The Diplomat and the James Martin Center for Nonproliferation Studies identified a complex at Kangson as the centrifuge facility’s suspected location (Panda 2018). A subsequent Washington Post article indicated that “there is a broad consensus among US intelligence agencies that Kangson is one of at least two secret enrichment plants” (Nakashima and Warrick 2018). In September 2020, the IAEA suggested that “If the Kangson complex is a centrifuge enrichment facility this would be consistent with the agency’s assessed chronology of the development of [North Korea’s] reported uranium enrichment programme” (International Atomic Energy Agency 2020, 5). However, recent independent analysis has raised doubts about the nature of the Kangson complex, suggesting that the site might instead be used to manufacture components for centrifuges (38 North 2021; Heinonen 2020). Without better public information or access to the site itself, it is not possible to confirm the nature of the Kangson site, or its potential role in North Korea’s nuclear weapons program. Given these uncertainties, it is unclear how much fissile material North Korea has produced and how many weapons it could potentially build.

The number of weapons depends not only on the amount of fissile material produced but also on the weapon design. It is unclear whether North Korea is prioritizing development and production of higher-yield thermonuclear weapons or lower-yield fission-only or boosted single-stage weapons. More powerful warheads with the high yield demonstrated in the single 2017 advanced design test would consume more fissile material if based on a composite warhead design or require special hydrogen fuel if based on a two-stage thermonuclear warhead design. Lower-yield single-stage fission weapon designs would require less fissile material. Such assumptions can result in very different estimates for the number of nuclear weapons. One assessment in 2020 concluded North Korea only had 10-20 nuclear weapons if it committed its fissile material to thermonuclear weapons production (Fedchenko and Kelley 2020). Another assessment concluded North Korea had around 40 weapons and only “very few thermonuclear bombs” (Hecker 2020; 38 North 2021).

Based on publicly available information, we assess that North Korea has produced sufficient fissile material to build 40 to 50 nuclear weapons (if all material is used) but has possibly assembled fewer than that. If so, most of those warheads would likely be single-stage fission weapons with possible yields of 10 to 20 kilotons demonstrated in the 2013 and 2016 tests and with at the most only a few thermonuclear warheads.

Assumptions about fissile material production and warhead designs also affect projections for how many nuclear weapons North Korea might have in the future and tend to result in inflated numbers. One study in 2021, for example, assumed North Korea might already have 67-116 nuclear weapons and projected the inventory might reach 151-242 nuclear weapons by 2027 (Bennett 2021). Others found the projection to be “much too high” (38 North 2021). It seems more plausible that North Korea might be capable of adding sufficient fissile material for a few to half a dozen nuclear warheads per year, which would potentially be sufficient to produce a total of approximately 80-90 weapons by the end of the decade.

Although North Korea is widely assumed to have developed warheads for its short-range ballistic missiles, there is less agreement about its ability to deliver functioning nuclear warheads with long-range missiles. These uncertainties are often overlooked in the public debate about North Korea’s nuclear capabilities. To better understand the status of North Korea’s nuclear weapons program and assessments about its warheads, it is useful to review major milestones and assessments from the last two decades or so.

North Korea apparently began to develop nuclear weapons even before the formal collapse of the Agreed Framework––a 1994 arrangement whereby the United States would provide Pyongyang two proliferation-resistant nuclear power reactors, and North Korea would freeze operations at reactors thought to be part of a nuclear weapons program. As publicly reported in 2004, Pakistan’s Abdul Qadeer Khan said that, some time around 1999, he was shown “three plutonium devices” during a visit to an underground facility about one hour outside Pyongyang (Sanger 2004). Three years later, then-US Secretary of State Colin Powell publicly stated: “We now believe they have a couple of nuclear weapons and have had them for years” (State Department 2002).

Less than a year later, on October 9, 2006, North Korea conducted its first nuclear test. The explosive yield was limited, less than one kiloton––not an impressive demonstration of a nuclear weapons capability and widely seen as a fizzle. The US intelligence community stated that the test produced a yield of “less than one kiloton––well below the yield of other states’ first nuclear test” (Office of the Director of National Intelligence 2007).

The second test––two and a half years later, on May 25, 2009––was a little more powerful and “suggests the North has the capability to produce nuclear weapons with a yield of roughly a couple kilotons TNT equivalent,” according to the US intelligence community.

These tests did not demonstrate the yield needed for operational nuclear weapons. A Rand Corporation report in 2012 cautioned: “It should also be considered that even speculative sources estimate that North Korea cannot have more than a few nuclear weapons available. If they exist, these devices are very precious to the regime, and it seems unlikely that they would be mounted on inaccurate and unreliable missile systems––the risk of ‘loosing’ a weapon is simply too high” (Schiller 2012).

Around the same time, the Defense Intelligence Agency––in an assessment distributed to members of Congress––for the first time concluded: “[The Defense Intelligence Agency] assesses with moderate confidence the North currently has nuclear weapons capable of delivery by ballistic missiles; however the reliability will be low” (Shanker, Sanger, and Schmitt 2013). The assessment did not reflect the conclusion of the US intelligence community as a whole and triggered an immediate rebuttal by the Defense Department: “It would be inaccurate to suggest that the North Korean regime has fully developed and tested the kinds of nuclear weapons referenced in the passage.” The Director of National Intelligence added that “the statement read by the member is not an intelligence community assessment” and that “North Korea has not yet demonstrated the full range of capabilities necessary for a nuclear-armed missile” (Clapper 2013).

Similarly, Air Force Global Strike Command stated in a briefing in September 2013 that North Korea “currently does not have an operational warhead; if developed, it could be deployed on” the Musudan (Hwasong-10), Taepo Dong-2, or Hwasong-13 (Air Force Global Strike Command 2013).3 Global Strike Command did not list any medium- or short-range missile with nuclear capability.

Even so, the assessment among private analysts at the time was that medium- and possibly short-range ballistic missiles were the first platforms for North Korean nuclear weapons. An April 2015 report from the US-Korea Institute at the Johns Hopkins School of Advanced International Studies, for example, claimed that the Nodong missile formed “the backbone of its current deterrent… ” (Schilling and Kan 2015). Similarly, after North Korea’s fifth nuclear test, in September 2016, demonstrated a yield of 10 to 15 kilotons, the Institute for Science and International Security estimated that “North Korea may have a handful of plutonium-based warheads for its Nodong ballistic missile” (Albright 2017).

But military commanders also appeared to go further than the intelligence community at the time. The commander of US Forces Korea, General Curtis Scaparrotti, stated in October 2014: “I believe they have the capability to miniaturize a device at this point and they have the technology to potentially deliver what they say they have.” Scaparrotti cautioned that “We’ve not seen it tested,” but nonetheless added, “I don’t think as a commander we can afford the luxury of believing perhaps they haven’t gotten there.” The Pentagon press secretary clarified: “General Scaparrotti said he believes they have the capability to miniaturize. That’s not the same thing as saying that they have the capability to mount, test, and deliver a nuclear weapon in an [intercontinental ballistic missile] (ICBM)” (Alexander and Stewart 2014).

The South Korean Ministry of Defense did not agree with Scaparrotti’s assessment. “Despite its significant technology level, we don’t think the North is capable of making such nuclear weapons,” a spokesperson said in February 2015 (Korea Herald 2015a).

The explanation was an important reminder to be cautious when interpreting official statements about North Korean nuclear capabilities. “Our assessment,” Gortney said, “is that they have the ability to put it on—a nuclear weapon on a KN-08 and shoot it at the homeland. And that—that’s the way we—that’s the way we think. That’s our assessment of the process (emphasis added). We haven’t seen them test the KN-08 yet and we’re waiting to do that. But it doesn’t necessarily mean that they will fly before they test it” (Defense Department 2015b).

And the last is a nuclear weapon that can survive that trip. Again, that’s what we don’t know. We don’t know the design specifics of his nuclear weapons—purported nuclear weapons. We don’t know if he’s been able to miniaturize it and make it stable enough.”

Despite the uncertainty about the number and ability to deliver a functioning nuclear warhead to the United States, some experts asserted that North Korea could do just that. Yet even after several ICBM flight tests conducted by North Korea in 2017, US Chairman of the Joint Chiefs of Staff Gen. Joseph Dunford in 2019 indicated North Korea had not yet demonstrated a capability to deliver a functioning nuclear warhead on a long-range missile. “I still see a potential although as-yet-undemonstrated capability to match a nuclear weapon with an intercontinental ballistic missile…” (Dunford 2019). A UN panel of experts reported in 2021 that an anonymous member state had assessed, “judging by the size of the missiles of the Democratic People’s Republic of Korea, that it is highly likely that a nuclear device can be mounted on the intercontinental ballistic missiles, and it is also likely that a nuclear device can be mounted on the medium-range ballistic missiles and short-range ballistic missiles.” But the size of a missile does not in and of itself show anything about the capability of the nuclear device it may be capable of carrying, so the member state cautioned that “it was uncertain whether the Democratic People’s Republic of Korea had developed ballistic missiles resistant to the heat generated during reentry” (United Nations 2021).

North Korea possesses several distinct types of short-range ballistic missiles (SRBMs), although many are part of the same missile “family” and therefore share common designs and characteristics. We have not yet seen authoritative information that North Korean SRBMs are nuclear capable, but this is a category of the missile force that is undergoing significant development, so they are included here for background. Moreover, in a speech in May 2021, Kim Jong Un stated that North Korea had developed what he described as “tactical nuclear weapons including new-type tactical rockets…” For the future, he stated it was necessary to improve the technology “and make nuclear weapons smaller and lighter for more tactical uses. This will make it possible to develop tactical nuclear weapons to be used as various means according to the purposes of operational duty and targets of strike in modern warfare…” (North Korean Ministry of Foreign Affairs 2021). The meaning of “tactical” is not clear. It could mean actual short-range tactical nuclear weapons or simply weapons that have shorter range than intercontinental weapons.

If North Korea had wanted to develop a deliverable nuclear weapon quickly, it could potentially have developed a crude gravity bomb for delivery by an H-5 (Il-28) medium-range bomber. This potential option is mentioned only for background; no public evidence suggests that North Korea has pursued it. A nuclear-capable coastal defense cruise missile, designated KN09, was listed in the 2013 briefing by the Air Force Global Strike Command, but was deleted in a subsequent revision (Kristensen 2013).

Bennett, B.W., et al. 2021. “Countering the Risk of North Korean Nuclear Weapons.” RAND and ASAN, April, p. 37. http://en.asaninst.org/contents/countering-the-risks-of-north-korean-nuclear-weapons/

Hecker, S. 2017. “What We Really Know About North Korea’s Nuclear Weapons, And What We Don’t Yet Know For Sure.” Foreign Affairs, December 4. https://www.foreignaffairs.com/articles/north-korea/2017-12-04/what-we-really-know-about-north-koreas-nuclear-weapons. [Google Scholar]

Jones, G. S. 2016. “The Implications Of North Korea Testing A Boosted Nuclear Weapon.” Proliferation Matters, January 11. http://nebula.wsimg.com/4da1b6db2152b55efe7334a70fe78781?AccessKeyId=40C80D0B51471CD86975&disposition=0&alloworigin=1. [Google Scholar]

Korea Herald. 2015b. “US Commander Says He Believes N. Korea Already Miniaturized Some Nuclear Weapons,” March 20. http://www.koreaherald.com/common_prog/newsprint.php?ud=20150320000162&dt=2. [Google Scholar]

North Korean Ministry of Foreign Affairs. 2021. ” Great Programme for Struggle Leading Korean-style Socialist Construction to Fresh Victory On Report Made by Supreme Leader Kim Jong Un at Eighth Congress of WPK,” January 9. http://www.mfa.gov.kp/en/on-report-at-eighth-congress-of-wpk/

Keywords: Hwasong, North Korea, Nuclear Notebook, ballistic missile submarines, ballistic missiles, nuclear weapons
Topics: Nuclear Notebook, Nuclear Weapons

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