Image: iStock/Alex Sholom

PROSPECTS FOR DPRK'S NUCLEAR USE SCENARIOS AND
DETERRENCE MEASURES OF THE US AND ROK ALLIANCE
Lee Sangkyu
Prepared for the

Project on Reducing the Risk of Nuclear Weapons Use
in Northeast Asia (NU-NEA)
Co-sponsored by
The Research Center for Nuclear Weapons Abolition, Nagasaki University (RECNA),
The Nautilus Institute for Security and Sustainability, and
The Asia-Pacific Leadership Network for Nuclear Non-Proliferation and Disarmament (APLN)
with cooperation ofPanel on Peace and Security of Northeast Asia
Additional funding by the MacArthur Foundation
February 18, 2022
[This article reflects the personal opinions of the author, not the official opinions of thegovernment of the Republic of Korea.]

Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA), Project Year 1

1About the Author
Professor Lee Sangkyu is a Republic of Korea (ROK) army officer and assistant professor at the
Korea Military Academy (KMA). His main research focus is the Democratic People's Republicof Korea’s (DPRK) nuclear threats, including its nuclear capabilities, strategies, and commandand control system. Professor Lee holds PhD and MS degrees in Nuclear Engineering from the
University of Utah in the United States. He has been an assistant professor in the Department of
Physics at KMA since 2019, and from 2017 to 2018 served as the Nuclear Policy Planning
Officer at the North Korea Policy Bureau, Ministry of National Defense, Republic of Korea.

Abstract
The purpose of this paper is to develop cases for the DPRK's use of nuclear weapons. As
background, firstly, the deterrence and countermeasure strategies of the United States-ROK
alliance in the face of the increasingly sophisticated DPRK’s nuclear threat is examined. Then,the DPRK's nuclear capabilities and nuclear strategy are investigated, and nuclear use cases arepresented in detail based on those strategies. The relative priorities and feasibility of the different
DPRK nuclear use cases were analyzed using parameters evaluating their military effect, thepotential for US nuclear retaliation, and the level of civilian casualties. Among the expectedcases, an attack on the ROK Mobile Corps would seem to be the most probable scenario, since
the benefits that the DPRK would gain from such an attack would be high. Within that case,there is a danger of nuclear provocation due to the asymmetry between the DPRK’s nuclear
possession and ROK’s possession of only conventional forces. The importance of the US
extended deterrence policy to deter the DPRK's nuclear threat is therefore emphasized, andmeasures to strengthen the credibility of US extended deterrence are also suggested.
Keywords: DPRK, Nuclear Capabilities, Nuclear Strategy, Nuclear Use Cases, US-ROK
Alliance

Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA), Project Year 12

I. Introduction (The US-ROK strategy)
The Republic of Korea (ROK) military has strengthened the US-ROK combined capabilities andposture with the United States, as well as its own capabilities and posture, to effectively deterand respond to the Democratic People's Republic of Korea (DPRK)’s nuclear and missile threats.
First, the US-ROK alliance has improved its combined deterrence and response measures basedon a joint “Tailored Deterrence Strategy (TDS),” implemented since 2016. 1 The TDS is abilateral deterrence and response strategy designed for the situation on the Korean Peninsula inconsideration of the characteristics of the DPRK’s leadership and nuclear and missile threats, and
it is a deterrence and response strategy that is one step more advanced than the general extended
deterrence concept provided by the United States. The TDS strategy includes military and nonmilitary countermeasures that include actions in the military, diplomatic, information, andeconomic domains. As such, TDS can be implemented in the full range of crisis scenarios, fromthe stage in which the DPRK threatens to use nuclear weapons to the stage in which nuclear
weapons are actually used, as shown in Table 1. 2

Table 1: Main Elements of the TDS at Various Stages of Nuclear Weapons Threat and Useby the DPRK 3
North Korean
ActionThreats to use
nuclearweapons
Nuclear use isimminent
Nuclear use

Alliance Response
US nuclear forces (strategic bombers, nuclear submarines equipped with ballistic
missiles) and conventional precision strike forces are deployed on or around the
Korean Peninsula, and additional ballistic missile defense assets are deployed.
Announcement of preemptive strike against DPRK’s nuclear-tipped missile units with
precision-guided weapons, preparations to strike DPRK’s nuclear power with US
nuclear weapons, and enhancement of readiness for the US nuclear posture.
Implement decisive countermeasures by the US-ROK national leadership.

Under the TDS, the concept of responding to the DPRK’s ballistic missile use is evolving basedon the capabilities of the US-ROK alliance. It is called the “US-ROK Alliance Comprehensive
Counter-Missile Strategy,” which is also known as the “4D operational concept.” 4“Comprehensive” here means improving the ability to respond to ballistic missile threats in allareas of detection, disturbance, destruction, and defense (4D). The two countries first agreed on
the 4D operational concept in 2014 and approved the implementation guidelines in 2015. The
guidelines are being developed in detail in five areas of the alliance’s decision-making, planning,command and control, exercise and training, and capability development. These deterrence andresponse strategies deployed by the US-ROK alliance have been systematized to be ready to

Yonhap News, “Establishment of the ROK-US tailored deterrence strategy and operational concept,” January 7,
2016.
2
ROK Ministry of National Defense, 2020 Defense White Paper (Seoul: Ministry of National Defense, 2016), 59.
3Yonhap news, “The main contents of the three-step tailored deterrence strategy and comparison by strategy,”
September9, 2016.
4ROK Ministry of National Defense, 2020 Defense White Paper (Seoul: Ministry of National Defense, 2020), 60~61.
1Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA), Project Year 1

3

respond to the DPRK's use of nuclear weapons, but US-ROK command and/or leadership are
required to make a decision to respond to DPRK nuclear weapons use.
Since 2018, along with the alliance capabilities, the ROK armed force has built a “WMD
Response System” consisting of a “strategic strike system” and the “Korean Air and Missile
Defense (KAMD)” to provide independent ROK deterrence and response capabilities. Before
development of the WMD Response System, the ROK had developed the “Triad system,” which
was made up of “Kill chain,” “Korea Massive Punishment and Retaliation (KMPR),” and“KAMD.” 5
The Kill chain was a striking system with the ambition of being able to disable the DPRK’s
nuclear and missile operations systems, including its missiles, mobile missile launchers,command and control systems, and relevant fixed installations. The main means of carrying out
these strikes were ground, surface, and subsurface-launched ballistic and cruise missiles, and airlaunched guided bombs and missiles, all targeted based on information provided by surveillance
and reconnaissance capabilities. The KMPR was also a striking system that was to be
implemented by directly targeting DPRK leadership, including its war headquarters, throughdeployment of missiles capable of simultaneous, massive-scale precision strikes, and special
operations units. 6 It was focused on developing a new missile launch system using largecapacity, high-performance conventional-explosive warheads and special operations units. After
2018, as a replacement of the Kill chain and KMPR, the “strategic strike system” has been
implemented as a deterrence strategy functioning by both denial and punishment to deter andcounter a full range of asymmetric threats. The main means features of the strategic strike system
are long-distance surveillance capabilities and precision strike capabilities.
The KAMD has been developed without major changes since before 2018. It is a multilayered
missile defense system that consists of a detection system, a command-and-control system, andan interception system. The main interceptor missiles used are upgraded Patriot missiles,
medium-range surface-to-air missiles (M-SAM), and long-range surface-to-air missiles (LSAM). M-SAM and L-SAM are being developed with the ROK own technology. The intercept
height of M-SAM is about 40km 7 and that of L-SAM is about 50~60km 8. As such, KAMD is
active responds to missile threats by constructing a multilayered missile defense system anddeveloping a ROK version of an “Iron Dome” as well. 9

II. The DPRK’s Nuclear Capability
The DPRK's current and future nuclear capabilities were well presented at the DPRK 8th Party
Congress held from January 5 to 12, 2021. DPRK Chairman Kim Jong-Un announced a
ROK Ministry of National Defense, 2016 Defense White Paper (Seoul: Ministry of National Defense, 2016), 58.
ROK Ministry of National Defense, 2016 Defense White Paper (Seoul: Ministry of National Defense, 2016), 59~60.
7Hankyoreh news, “Succeeded in intercepting surface-to-air missiles under development in South Korea,” March
18, 2016.
8
Donga ilbo news, “Ballistic missile defense, L-SAM, to be prototyped by 2024,” December 4, 2019.
9
Chosun ilbo news, “Promoting domestic development of 'Korean-style iron dome' that catches North Korean longrange artillery... 2035 deployment,” June 28, 2021.
5
6

Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA), Project Year 1

4

summary report in four areas during the Congress; First, a review of the Party’s work since the
7th Congress, second, the advancement toward building domestic socialist power, third, theprogress of independent reunification and external relations, and fourth, the strengthening of theParty programs. 10 In the report, details on strengthening nuclear deterrence are presented for thefollowing:•

Development of nuclear-powered submarines•

Improvement of the accuracy of the 15,000 km intercontinental ballistic missile (ICBM)•

Individual guidance technology for multiple warheads•

Development of ground and sea launch intercontinental ballistic missiles with solid-fuelengines•Development of tactical nuclear weapons•

Production of very high yield nuclear warheads

As such, a lot of content about the augmentation of the DPRK’s nuclear force was provided
during the Congress. In particular, in the “achievements” session, it was stated that “theaccumulated nuclear technology was further advanced, so nuclear weapons are miniaturized andstandardized. Developed nuclear weapons can be implemented for tactical weaponization, andhigh yield hydrogen bombs were developed. On November 29, 2017, the Party Central
Committee proudly declared to the world the national nuclear force, with the great success of thetest launch of the intercontinental ballistic missile, Hwasong-15.” 11In the “advancement toward building domestic socialist power” session of the Congress, it was
mentioned that “We will develop tactical nuclear weapons that can be applied in a variety ofways according to the purpose of operational missions and targets in modern warfare by further
advancing nuclear technology. By continuously pushing forward with the production of very
high yield nuclear warheads, it is necessary to maintain initiative and thoroughly deter, control,and manage various military threats in the Korean Peninsula, which is inevitably accompanied
by nuclear threats.” 12As such, the DPRK emphasized the current status of nuclear weapons andnoted the tactical nuclear weapons and high-yield nuclear weapons to be developed in the future.
Peacetimes, “[8th Party Congress] Summary of business summary report (full text),” January 9, 2021.
Ibid.
12
Ibid. The 8th Party Congress report includes the following messages of tactical weaponization and tactical nuclear
weapons. In the second part of the report (“Current achievements”), it states "총결기간 이미 축적된 핵기술이더욱 고도화되여 핵무기를 소형경량화, 규격화, 전술무기화하고 초대형수소탄개발이 완성되였으며", forwhich the English translation is "During the previous congress period, the nuclear technology that had alreadybeen accumulated was further advanced, so it was completed that making nuclear weapons smaller and lighter,standardized, and tactical weaponization, and the development of super-large hydrogen bombs.” In the fourthpart of the report (“Future plans”), it states "핵기술을 더욱 고도화하는 한편 핵무기의 소형경량화,전술무기화를 보다 발전시켜 현대전에서 작전임무의 목적과 타격대상에 따라 각이한 수단으로 적용할수있는 전술핵무기들을 개발하고 초대형핵탄두생산도 지속적으로 밀고나감으로써", for which the English
translation is: "While further advancing nuclear technology, we will further develop miniaturization and tactical
weaponization of nuclear weapons to develop tactical nuclear weapons that can be applied in various ways
10
11

Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA), Project Year 1

5

The main terms, mentioned in the above statements, are miniaturization, tactical weaponization,
tactical nuclear weapon, high yield hydrogen bomb, and very high yield nuclear warhead. The
use of terms in the DPRK’s 8th Party Congress and other statements were analyzed based on the
DPRK's level of nuclear technology. Thus, miniaturization means reducing the size and weightof nuclear warheads to be able to load them on missiles. Technically, doing so means reducing
the diameter of the nuclear warhead to less than one meter so that it can be mounted on mediumrange and short-range missiles and to reduce the explosive power to about ten kiloton or less.
With that, the total mass of a warhead is lighter than a few hundred kilograms. Next,
standardization means unifying the specifications and material types of various nuclear weapons
components so that mass production is possible.
Tactical weaponization means using the nuclear warheads disclosed on March 9, 2016, (seeFigure 1) with short-range missiles such as SCUD and KN-23·24 for tactical purposes. The KN23, which was test-launched first in 2019, has a diameter of 0.95 m and a payload weight ofabout 500 kg, and the KN-24 is estimated to have a diameter of 0.7 to 0.85 m and a payload
weight of 400 to 500 kg. Therefore, the hydrogen bomb unveiled in 2017 is limited in the degree
that it can be loaded on missiles, and only the nuclear warhead unveiled in 2016 might bemounted on the KN-23 or KN-24.

depending on the purpose of operational missions and targets in modern warfare, and continue to push forward
the production of super-large nuclear warheads."

Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA), Project Year 1

6Nuclear warheads announced on Mar. 9,

Nuclear warheads announced on Sept. 3,

2016. 132017. 14Warhead type: fission bomb, boosted fissionbomb

Warhead type: hydrogen bomb

Diameter: about 0.6m
Weight: about 400kg
Yield: 10kt

Size: width 0.8m × length 1.3m
Weight: about 700kg
Yield: 50kt

* The above data are estimated based on ROK government announcements and media reports.

Figure 1:The DPRK's Developed Nuclear Warheads 15
Tactical weaponization denotes tactical use of an existing nuclear warhead, on the other hand,creating a tactical nuclear weapon means developing new weapons. The size of the tactical
nuclear warhead should be further reduced in size for mounting on a weapon that can be fired bya large multiple rocket launcher, such as the KN-25 short-range ballistic missile, or on longrange artillery such as 240mm or 170mm rounds. The reason that size reduction is needed is thatthe outer diameter of the KN-25 is about 0.6 m and the payload is about 300 to 400 kg, 16 so thepreviously developed fission bomb is too large to be loaded. Therefore, it is necessary for the
DPRK to develop a new type of more miniaturized nuclear warhead for a tactical nuclear
weapon. Considering the DPRK's technological level, it will be possible to develop tactical

Hankook ilbo news, “How far does Kim Jong-un's confidence in the miniaturization of nuclear warheads go?”March 9, 2016.
14
Hankook ilbo news, “Kim Jong-un visits the nuclear weapons research center and unveils the nuclear warhead(hydrogen bomb) of the Hwasong-14,” September 3, 2017. The yield shown is that included in official ROK
government announcements, although there are other opinions about the probable yields of DPRK nuclear
weapons.
15
Lee, Sangkyu, “Possibility of DPRK’s Tactical Nuclear Development and its implications in terms of Nuclear
Strategy and Nuclear Command and Control,” Defense and Technology, March 2021.
16
Missile Threat, CSIS Missile Defense Project, “Missiles of the World > North Korea > KN-25,” last updated July 31,
2021, https://missilethreat.csis.org/missile/kn-25/
13Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA), Project Year 1

7

nuclear weapons that can be mounted on long-range artillery and short-range missiles within a
few years. 17
The high yield hydrogen bomb, which the DPRK tested in 2017, is expected to be mounted on
ICBM-class missiles such as the Hwasong-15 and -16, as well as and SLBMs (submarinelaunched ballistic missiles) such as Pukguksong. The mention of a very high-yield nuclear
warhead means that a hydrogen bomb with explosive power improved to the hundreds ofkilotons range is to be developed in the future and will be mounted on ICBMs and SLBMs as
well. As such, the DPRK is expected to possess a variety of nuclear weapons that can be used invarious situations within a few years.

III. DPRK’s Nuclear Strategy and Nuclear Use Scenarios
It is necessary to review the DPRK's nuclear strategy to project cases under which it might use
nuclear weapons. The DPRK’s nuclear strategy is analyzed based on the DPRK's laws, military
strategies, statements, and nuclear capabilities. To start with the conclusion, it is expected thatthe DPRK will choose an asymmetric escalation nuclear strategy, which is very offensive, toeffectively deter the US-ROK alliance. The reason is that the DPRK is far inferior to the UnitedStates in terms of the level and quantity of nuclear weapons technology, and its conventional
force is also lacking in many areas compared to the combined forces of the US-ROK alliance.
Therefore, to make up for this inferiority, an offensive nuclear strategy will be inevitably used toinduce the US-ROK alliance to take passive actions. Such coercion tactics are the best deterrence
strategy for the DPRK to achieve a strategic balance with the US-ROK alliance.
A representative example of the DPRK's offensive nuclear strategy is not to adopt the principleof ‘No-First-Use’ of nuclear weapons. These details can be confirmed by looking at the relevantlaws and the statements so far. According to the fifth paragraph of the ‘Act on the Consolidationof the Status of a Self-Defense Nuclear Power State’ announced in 2013, “The Democratic
People’s Republic of Korea does not use or threaten nuclear weapons against non-nuclear
countries unless it engages in an offensive action against the DPRK in alliance with other hostile
nuclear states.” At first glance, the DPRK appears to be adopting the principle of “No-FirstUse.” However, it presents prerequisites and specifies the possibility of a nuclear attack on the
ROK. With that in mind, Kim Jong-Un mentioned the possibility of a preemptive use of nuclear
weapons during the test-firing of the Hwasong-10 missile on June 23, 2016, as follows: “Weshould continue to expand and strengthen our preemptive nuclear strike capabilities and continue
to research and develop various strategic attack weapons.” 18
It was also announced at the 8th Party Congress that “the goal of advancing the nuclear
preemptive and retaliatory strike capabilities was presented. The national defense force has risen
to a level where it can preemptively suppress threats to hostile forces.” As such, the DPRK has
made several statements suggesting the possibility of a preemptive use of nuclear weapons. From
Tactical nuclear weapons developed by the DPRK may be “gun-type” weapons using U-235 as the DPRK’s stocks
of enriched uranium increase.
18
Hankoyreh, “North Korea declares successful test launch of medium-long-range missile ‘Hwasong-10,’” June 23,
2016.
17

Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA), Project Year 18the laws and official statements made public so far, it is evident that the DPRK is adopting athreatening and offensive nuclear strategy.
In addition, in the concept of the DPRK’s military strategy, it is basically adopting offensive
strategies such as ‘bolt out of the blue warfare,’ ‘combination of regular and irregular warfare,’and ‘lightning war.’ 19 To effectively use this military strategy, an offensive and asymmetricnuclear strategy will be combined. The bolt out of the blue warfare strategy adopts a surprise
attack by selection of the time, means, and place of the attack in order to seize the initiative. For
this, most of the DPRK military forces are deployed south of the Pyongyang-to- Wonsan line,
and a large number of long-range artillery units are deployed in the southern DPRK. 20 If some ofthese long-range artillery units were entrusted with tactical nuclear weapons, the threshold forusing nuclear weapons would be lowered, 21 which would pose a direct threat to the US-ROK
alliance. Accordingly, even in small-scale military conflicts such as local provocations, the crisis
precipitated by such conflicts might be expected to escalate rapidly. The purpose of the DPRK's
combination of regular and irregular warfare is to prevent the US-ROK alliance from
replenishing their combat power and to exhaust the combat power present in the ROK at an earlystage by simultaneously striking front and rear battlefields. In particular, the ROK must defend
ports and airfields in the rear area where US reinforcements will come in as strongly as it
defends the first front line. Therefore, it can be expected that the DPRK will threaten or actuallyuse nuclear weapons against major ports, airfields, and industrial facilities that produce military
supplies for the purpose of weakening the operational continuity of the US-ROK alliance.
The effect of the DPRKs tactical nuclear weapons on its nuclear strategy is as follows. If the
DPRK develops and deploys tactical nuclear weapons they will take a more offensive nuclear
posture, including high-strength provocation and coercion, to change the status quo. For instance,
they will use tactical nuclear weapons in all areas of strategic, tactical, and operational plans by
combining the capabilities of these weapons with the DPRK’s offensive military strategy. Firstof all, if the DPRK's internal unrest increases, the DPRK military may conduct high-intensity
provocations using conventional weapons targeting the ROK. With that, there is a possibility of
threatening by using tactical nuclear weapons as a means of deterrence in case of conventional
provocations. 22 A typical example of this is Russia's annexation of Crimea in 2014. At the time,
the Russian foreign minister threatened the deployment of tactical nuclear weapons, leading theconflict to an advantageous situation. 23Along with that the use of tactical nuclear weapons as ameans of deterrence, there is a possibility that a paradoxical situation of stability and instability
Kim Tae-hyun. "A Study on the Change of north Korean Military Strategy: Risk Management against Mismatch ofStrategy," Journal of Strategic Studies, 22-2 (2015): 167-204.
20
Unification Education Center, Ministry of Unification, 2018 Understanding North Korea (Seoul, 2017), pp. 97-99.
21
Several studies have pointed out and are concerned about this possibility. An example is Hyeongpil Ham (2021),“North Korea’s Evolving Nuclear Posture: Strategic Implications of Pyongyang’s Tactical Nuclear Weapons
Development,” KIDA (in Korean), dated October 15, 2021, and available ashttps://www.kida.re.kr/frt/board/frtPolicyStudyBoardDetail.do?sidx=363&idx=1195&depth=4&lang=kr
22
If the DPRK perceives that the credibility of extended deterrence by the United States cannot be guaranteed, it
may misjudge that the United States will not guarantee the use of nuclear weapons at a similar level (low yield) tothose used by the DPRK on the Korean Peninsula, leading the DPRK to believe that it could use nuclear weapons
without being attacked with nuclear weapons in return.
23
Ajou Economic Daily, “Russian Foreign Minister Suggests ‘Possibility of Tactical Nuclear Deployment in Crimea,
Ukraine,’” December 16, 2014.
19

Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA), Project Year 1

9may arise on the Korean Peninsula, in the same way that small-scale disputes between India andPakistan using conventional arms have increased since Pakistan has possessed nuclear weapons.
This may be a reason for major military targets, such as the ROK Mobile Corps, to be selectedby the DPRK for tactical nuclear weapon attack.
In addition, the DPRK might use tactical nuclear weapons as a means of coercion to change thestatus quo, such as seizing the initiative in the Korean Peninsula and in reunification after
securing nuclear deterrence against the United States with their strategic nuclear weapons. To doso, they will deploy short-range missiles and multiple rocket launchers equipped with nuclear
warheads, and then they might threaten the use of nuclear weapons and limit the strategic optionsof the US-ROK alliance or use nuclear weapons in wartime to secure initiatives.
Based on this perception of the DPRK's nuclear strategy, several nuclear use cases were preparedas shown in Table 2. The cases were evaluated with regard to three parameters: military effect,
US nuclear retaliation, and civilian casualties. Military effects and US nuclear retaliation werechosen with benefits versus costs in mind from a deterrence perspective. The attribute of
avoiding US nuclear retaliation is scored high when the likelihood of US nuclear retaliation islow. The reason for including civilian casualties in the analysis is because Kim Jong-Un would
consider environmental and historical evaluations, as well as political, military, and diplomatic
factors, directly related to civilian casualties in the process of his decision to use nuclear
weapons. The cases were divided into direct nuclear use and nuclear use to produce EMP(electromagnetic pulse) effects. For direct nuclear targets, the ROK Mobile Corps, Jinhae Naval
Base, and Seoul, where the Ministry of National Defense and Joint Chiefs of Staff are located,
are selected. In addition, the US military base in Pyeongtaek is also selected.
For the EMP attack, the high seas near Wonsan, the DMZ, and Busan Port were selected. The
priority of the attack cases was evaluated as shown in Table 2 based on the three parameters. In
the evaluation, five points were the highest point rating and one point was the lowest rating foreach parameter. The case deemed the most probable based on this analysis was a direct attack on
the mobile corps, followed by an EMP attack at the DMZ, a direct attack on the Jinhae Naval
Base, and an EMP attack at the port of Busan.

Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA), Project Year 1

10

Table 2:The DPRK's Potential Nuclear Use Cases and Priorities
MilitaryeffectAvoiding US
Nuclear
Retaliation

Minimizing
CivilianCasualties

Overall
Priority
Rank (total
score)ROK Mobile Corps

5

3

5

1 (13)Jinhae Naval Base

5

3

2

3 (10)

Seoul

4

2

1

7 (7)

Pyeongtaek(US military base)

5

1

2

6 (8)

High seas near
Wonsan

1

4

4

5 (9)

DMZ

4

3

4

2 (11)

Busan port

3

3

4

3 (10)

Targets

DirectNuclear
Use

EMP
Attack

The four most probable cases are analyzed in detail as follows. The highest-rated case is that the
ROK Army Mobile Corps would be attacked directly in the northern region of Gyeonggi-do witha nuclear weapon of 10-20 kt, although other weapons combinations and attack options are
possible. The DPRK may intend to end the war early in an advantageous situation by disabling
the main force of the ROK military forces and thus make ROK counter-attack operations
impossible. It is expected that the nuclear attack will cause direct damage to personnel andequipment, and consequent loss of combat power. In addition, northern Gyeonggi-do and parts ofGangwon-do will be contaminated with fallout. 24
The second highest-rated case is designed to cause wide range damage from an EMP caused by ahigh-altitude nuclear explosion near the DMZ at the beginning of the war. If the DPRK detonates
a 20 kt yield nuclear weapon at an altitude of 60 km using a ballistic missile such as the SCUD
or KN-23, the surrounding region will be affected by an EMP to a radius of up to about 800 km
from the location of the explosion.25 Unfortunately, because of the direction of the geomagnetic
field on the Korean Peninsula, a stronger EMP is created in the South than in North, thus the
EMP would cause more damage in Seoul than North of the DMZ. In addition, in general, theROK is more reliant on technologies that are vulnerable to EMPs than is the DPRK. The DPRK's

This type of damage could occur with either ground burst or air burst weapons detonation, though not withhigh-altitude explosions. Depending on the height of the explosion, an air burst could also cause some fallout.
Fallout would create a wider range of contaminated areas than the areas where the detonation would have direct
lethal impacts.
25
There are many studies and articles describing the potential for the DPRK to use nuclear weapons to create
EMPs with high-altitude explosions. These include Peter Vincent Pry, North Korea: EMP Threat, North Korea’s
Capabilities for Electromagnetic Pulse (EMP) Attack, (US) EMP Task Force on National and Homeland Security, June
6, 2021, https://emptaskforce.us/wp-content/uploads/2021/06/REPORTempthreatNK21A.pdf; and Peter Vincent
Pry, “North Korea EMP Attack: An Existential Threat Today,” The Cipher Brief, August 22nd, 2019,https://www.thecipherbrief.com/column_article/north-korea-emp-attack-an-existential-threat-today
24

Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA), Project Year 1

11intention might be to cause social chaos by neutralizing the national core infrastructure in Seoul,
as well as to neutralize the command and communication system of the ROK military. 26
In the 3rd and 4th-ranked cases, the attack targets are the Jinhae Naval Base and the port of Busan.
Jinhae and Busan are geographically very close. These two cases differ depending on whether it
is a direct nuclear attack or a situation in which only EMP is induced by detonating a nuclear
weapon at an altitude of 50 km. In both cases, however, the DPRK's intended purpose might besimilar, as follows. The purpose is to delay the deployment of the US mainland reinforcements
and UN forces entering through major ports and to incapacitate the ROK’s core national
infrastructure, because Busan is the second largest city of the ROK. Through this, the DPRK will
try to end the war prematurely by weakening the ROK’s ability to sustain the war. As such, inthese cases, the DPRK's use of nuclear weapons is not primarily to deter the offensive strategy of
the United States and ROK, but rather because the DPRK perceives that the use of nuclear
weapons will be effective from a warfighting standpoint.
Since all of the aforementioned DPRK's nuclear use cases are assumed to be used in the Korean
Peninsula, short-range missiles will be used as a means of delivery. The DPRK has not yet
declared the actual deployment of nuclear weapons, so it is unclear exactly which missiles will
be equipped with nuclear warheads. 27 Based on the recently tested missiles with improved
accuracy, however, some SRBMs can be expected to be equipped with a nuclear warhead ofseveral tens of kilotons in the future, that is, by around 2030.
The SRBMs most likely to carry a nuclear warhead are the SCUD-MaRV (Maneuverable
Reentry Vehicle), KN-23 and KN-24. The SCUD-MaRV is a SRBM with a range of 450 km andhas distinctive forward fins, presumably to add a terminal guidance capability for increased
maneuverability and accuracy. 28 It is estimated to be 13.5 m long and 0.88 m in diameter. It will
therefore be sufficient to carry the fission bomb tested by the DPRK in 2016. The KN-23 has alength of 7.5 m, a diameter of 0.95 m, and a payload of 500 kg. 29 It was first tested in 2019 andhas a range of about 690 km. It is characterized by its resemblance to the Russian Iskander-M,
which can do the “pull-up” maneuver in its terminal phase of flight to lower the probability ofinterception.
The KN-24 is classified as a SRBM with a range of 410 km, but the DPRK has listed it as a
missile that can be fired from a super-large multiple rocket launcher. Its appearance is similar tothat of the US ATACMS (Army Tactical Missile System). The length of KN-24 is 4.57-5.55 m

See for example, Bruce Dorminey, “North Korean EMP Attack Would Cause Mass U.S. Starvation, Says
Congressional Report,” Forbes, October 23, 2017,https://www.forbes.com/sites/brucedorminey/2017/10/23/north-korea-emp-attack-would-cause-mass-u-sstarvation-says-congressional-report/?sh=16fe4c8e740a
27
It has been suggested that it might be possible for the United States, through satellite surveillance, to identify
nuclear missiles as the DPRK brings them out of storage for use. It is questionable, however, whether it is possible
to completely distinguish between conventional warheads and nuclear warheads during transport.
28
Missile Threat, CSIS Missile Defense Project, “Missiles of the World > North Korea > KN-18 (Scud MaRV),” last
updated July 31, 2021, https://missilethreat.csis.org/missile/kn-18-marv-scud-variant/29
Missile Threat, CSIS Missile Defense Project, “Missiles of the World > North Korea > KN-23,” last updated July 31,
2021, https://missilethreat.csis.org/missile/kn-23/
26

Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA), Project Year 112and the diameter is about 0.7-0.85 m. 30 The payload is estimated to be 400-500 kg, so it might
carry a small nuclear warhead when used tactically.
In addition to short-range missiles, there is a possibility of using SLBMs such as the
Pukguksong-3 to attack the rear area of the ROK, such as the Busan Port. The Pukguksong-3 hasa range of 1,900 km 31 and is expected to be able to carry large warheads such as hydrogenbombs.
It should be emphasized that in considering these use cases, warfighting and deterrence need tobe distinguished. The US Strategic Command, for example, has separate divisions for these twofunctions. The reason why weapons such as ICBMs and MIRVs (multiple independent reentry
vehicles) were developed by the DPRK seems to be to secure deterrence against the UnitedStates. With such deterrence, the DPRK likely calculates that it could weaken the US extended
deterrence and ultimately induce decoupling between the United States and the ROK. If theUnites States’ extended deterrence is weakened, the possibility of the DPRK's use of nuclear
weapons on the Korean Peninsula will increase further.

IV. Deterrence and Response Measures Against DPRK's Nuclear Use
The DPRK's advanced nuclear capability and its offensive nuclear strategy are a great threat to
the US-ROK alliance. Deterring these threats is not easy, and deterrence usually works when the
provoking state feels that the costs outweigh the benefits. In the case of deterrence withconventional forces alone, however, the possibility of deterrence failure increases due to theasymmetry. Therefore, to effectively deter the DPRK's intention to use nuclear weapons, it isimportant to increase the credibility of the US extended deterrence policy. However, if there isdoubt in the credibility of the extended deterrence, the deterrence effect will decrease, so there
will be a risk that the DPRK’s nuclear use cases will become reality.
The main challenges of the extended deterrence are known as “de Gaulle's Doubts,” “A Leaky
Umbrella,” the “Healey Theorem,” “Status Quo Ante,” 32 and “Putting the Cart before theHorse.” First, “De Gaulle’s doubt” originated from the question of Charles de Gaulle, a French
general and president, during the Cold War, when he felt that the United States would not risk
New York or Detroit to save Hamburg or Lyons. 33 By the same logic, there could be a question
whether the United States would sacrifice its own cities like Los Angeles or San Francisco todefend Seoul. As the DPRK develops ICBMs capable of hitting the US mainland, these
suspicions have grown. As such, it raises doubts about the ability to implement the nuclear
umbrella and may eventually lead to decoupling of the ROK-US alliance. In addition, if the
DPRK has the same suspicion that the United States may not be willing to keep its alliance
Missile Threat, CSIS Missile Defense Project, “Missiles of the World > North Korea > KN-24,” last updated January
18, 2022, https://missilethreat.csis.org/missile/kn-24/
31
Missile Threat, CSIS Missile Defense Project, “Missiles of the World > North Korea > Pukguksong-3 (KN-26),” last
updated July 31, 2021, https://missilethreat.csis.org/missile/pukguksong-3/
32
Justin V. Anderson, Jeffrey A. Larsen, "Extended Deterrence and Allied Assurance: Key Concepts and Current
Challenges for U.S. Policy," INSS Occasional Paper, USAF Academy, September 2013, 73-79.
33New York Times, “The De Gaulle Nuclear Doctrine is Alive in Paris,” May 6, 1981.
30

Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA), Project Year 1

13

commitments, there is a possibility that the DPRK perception of the situation may cause it tomisjudge that the United States will not help the ROK, and that US deterrence will thus fail.
Efforts are therefore required to resolve the so-called “De Gaulle’s doubt” and increase thecredibility of the US commitment to extended deterrence.
Second the “Leaky umbrella” challenge refers to the United States possibly not deploying
sufficient military forces (conventional, nuclear, and missile defense) to prevent a potential
adversary from targeting its allies, or may not be able to mount an adequate level of militaryresponse to a provocation. 34 Therefore, there is a perception that the alliance guarantee may not
be possible to support with conventional power and missile defense alone, especially for allies
that are directly threatened by nuclear weapons. As a representative example, the United States
deployed tactical nuclear weapons to the ROK for thirty-three years from 1958 to 1991. The
largest number of tactical nuclear weapons in the ROK was about 950 in 1967. 35 However, after
the end of the Cold War in 1991, the United States withdrew all nuclear weapons from the ROK
as the strategy for deploying nuclear weapons abroad changed. As the DPRK continues toadvance its nuclear capabilities, there is a demand that “nuclear must be deterred with nuclear,”and there is a debate among the South Korean people about demanding the redeployment oftactical nuclear weapons in the ROK by the United States. In such a situation, the US-ROK
alliance is bound to be concerned about an effective and appropriate level of nuclear deterrence.
In particular, those in the ROK (or, for example, Japan) who feel threatened by the DPRK will be
more concerned about the credibility of the United States’ commitment to extended deterrence.
There is a difference in perspective between the ROK and United States in this regard. For
example, when the United States retired its nuclear-tipped cruise missiles in 2010, the ROK andJapan strongly opposed the move. This was the trigger for the launch of the US-ROK Deterrence
Strategy Committee (DSC). The same considerations may have been behind the restoration of
low-yield nuclear weapons in the United States’ 2018 Nuclear Posture Review.
Third, Denis Healey, who was British Secretary of Defense from 1964 to 1970, said, “it takes
only 5% credibility of American retaliation to deter the Russians, but 95% to reassure theEuropeans,” 36 and that statement became the background of the “Healy Theory.” Since
deterrence strategies are based on anxiety and fear, those who feel fear easily are deterred even if
they have low trust. Therefore, there is an opinion that the United States should put considerable
effort into securing the alliance because its allies feel the threat of the enemy is greater than theguarantee of the alliance provided by the United States. In particular, in 2016, when the DPRK’s
nuclear threat was growing, the US military conducted a rotational deployment of strategic assets
to enhance the credibility of its extended deterrence on the Korean Peninsula, despite the highcost of deploying strategic assets.
Fourth, “Status Quo Ante” means that the allies wish the extended deterrence and allianceguarantee policies to be maintained at the same level as in the past. This is similar to a physical
The term "Leaky Umbrella" is used in Justin V. Anderson, Jeffrey A. Larsen, and Polly M. Holdor, “Extended
Deterrence and Allied Assurance: Key Concepts and Current Challenges for U.S. Policy,” published by the USAF
Institute for National Security Studies, USAF Academy, Colorado as INSS Occasional Paper 69, September 2013,https://www.usafa.edu/app/uploads/OCP69.pdf
35
Hankoyreh, “What is the tactical nuclear weapon that makes the Korean redeployment controversial?”
September13, 2017.
36
Dennis Healey, The Time of My Life, London: Michael Joseph, 1989, 243.
34

Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA), Project Year 1

14phenomenon that maintains the current state and resists change, such as the moment of inertia. A
representative example of such a phenomenon in the security sphere is the concern expressed byallies about policy changes in the 2010 US Nuclear Posture Review (NPR) that emphasized the
reduction of the role of nuclear weapons. 37 Because of the policy, the United States had retired
nuclear tipped Tomahawk cruise missiles. The ROK and Japan recognized the missile as one of
the core armaments of the nuclear umbrella providing a key means of deterring nuclear and
WMD threats from DPRK, China, and Russia. In response, Japan expressed concern about the
reduction of the US nuclear deterrent in a US-Japan security meeting, and the US-ROK
Extended Deterrence Policy Committee (EDPC) was launched in 2012 to strengthen security
cooperation. This can be said to reflect the unstable psychology of a country that does not haveadequate deterrence measures.
Lastly, “Putting the Cart before the Horse” means that the allies do not feel the necessity ofpossessing their own nuclear weapons only when they perceive it to be safe to forego that choice,and thus extended deterrence fails as a means of non-proliferation in situations where they do not
feel safe. That is, if extended deterrence is emphasized only as a means of securing nonproliferation, without a guarantee of alliance as well, it may not be successful in securing nonproliferation. In the NPR, the United States emphasizes that extended deterrence contributes tomaintaining a nuclear non-proliferation regime by providing its allies with extended deterrence
so that their allies do not feel the necessity to develop nuclear weapons. In particular, according
to the Nuclear Non-Proliferation Treaty (NPT), the international community distinguishes
between nuclear and non-nuclear states, and non-nuclear states are prohibited from developing
and possessing nuclear weapons. Therefore, allies that cannot develop nuclear weapons and do
not possess reliable means of deterring nuclear threats on their own are making the sacrifice ofabandoning nuclear development because they believe in the security guarantee from the UnitedStates. In such a situation, if the United States emphasizes its role only in the aspect of nuclear
non-proliferation without a clear and credible commitment to provide extended deterrence,dissatisfaction among allies will inevitably arise.
Along with that, there is a skeptical view of extended deterrence due to the recognition of theaforementioned challenges. An American scholar, Jeffrey Lewis, said, “The nuclear umbrella
does not exist and the United States has no obligation to use nuclear weapons under certain
circumstances. The extended deterrence is nothing more than a political rhetoric that our allies
want to hear.” 38 There are such skeptical perceptions and concerns about extended deterrence in
the ROK as well. In this regard, it is suggested to enhance the credibility and implementation ofextended deterrence as follows. 39
Frequently discussed options to enhance the credibility of extended deterrence are redeploymentof the US tactical nuclear sharing and making an operational plan using nuclear weapons.
However, these methods are not feasible in the near future considering the policy direction of the
ROK and the characteristics of the US nuclear command and control system. Therefore, topropose realistic and reasonable measures, the framework of extended deterrence, which
United States Department of Defense, 2010 Nuclear Posture Review, 2010, 15.
Lewis, Jeffrey, “Rethinking extended deterrence in Northeast Asia.” Nautilus Institute workshop, 2010.
39
Similar concerns were expressed in Davis, Paul K., Jeongeun Kim, Junho Park, and Peter A. Wilson, “Deterrence
and Stability for the Korean Peninsula,” Korean Journal of Defense Analysis, 28(1), 1-23, 2016, available athttps://www.researchgate.net/publication/298716189_Deterrence_and_Stability_for_the_Korean_Peninsula
37
38

Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA), Project Year 1

15

includes the concepts of “political resolve,” “political and military support,” and “militarycapabilities” were reviewed. 40
In terms of political resolve, to strengthen extended deterrence, a joint declaration between the
ROK and the United States and diplomacy between the nations’ leaders may be considered. In
particular, the strengthening of extended deterrence can be emphasized in a specific and strong
tone in a joint declaration at a summit meeting between the presidents of the United States andthe ROK. In addition, security guarantees for alliances and the tailored deterrence strategy may
be specified in national strategic guidelines such as the US National Security Strategy and the
NPR. 41
For political and military support, various security consultative bodies such as the US-ROK
Security Council, Deterrence Strategy Committee, and Extended Deterrence Policy Committee
should be continuously developed to strengthen the common understanding between the ROK
and the United States. For example, in the preamble to the 52nd SCM (Security Consultative
Meeting) in 2020, “The Secretary and the Minister committed to ensure that the Alliancedeterrence posture remains credible, capable, and enduring. To this end, the two leaders pledged
to enhance deterrence through the implementation of many of the policy recommendations fromthe Extended Deterrence Joint Study.” 42 Based on the statement, it is necessary to further
strengthen the deterrence effect by implementing the policy suggestions of the joint researchthrough the deterrence consultative bodies. And above all, the presence of US forces in Korea
exerts a very important deterrence effect. Therefore, the solidity of the alliance needs to be
demonstrated and the continued presence of US forces in the ROK needs to be confirmed. In
addition, normalizing the reduced US-ROK joint exercise and rotational deployment of strategic
assets could be one way to strengthen deterrence.
Finally, military capabilities can be a decisive means to directly increase the credibility of theextended deterrence. In the 2018 NPR, the United States announced the development of lowyield SLBMs and sea-launched cruise missiles (SLCMs), and it mentioned that these low-yield
SLBMs and SLCMs would strengthen the assurance of deterrence to the Asian alliances. 43 44 To
ensure nuclear deterrence in Europe, the United States deployed B-61 gravity nuclear bombs tofive NATO countries (Germany, Belgium, the Netherlands, Italy, and Turkey) and adopted
nuclear sharing using the dual-purpose aircraft of those countries. On the other hand, after thewithdrawal of tactical nuclear weapons from the ROK, strategic nuclear weapons became ameans of guaranteeing nuclear deterrence, and the reliance on these weapons has raised doubts
Justin V. Anderson, Jeffrey A. Larsen, “Extended Deterrence and Allied Assurance: Key Concepts and Current
Challenges for U.S. Policy,” INSS Occasional Paper, USAF Academy, September 2013, 9-31.
41
Although there is unlikely to be a fundamental solution to strengthening extended deterrence due to a gap in thecredibility of the US deterrence policies, the efforts of both countries to reinforce their alliance should continue ata level that each can accept.
42
Yonhap News, “Joint Statement of the 52nd ROK-U.S. SCM,” October 15, 2020.
43
US Department of Defense, 2018 Nuclear Posture Review, 2018, 12.
44
The addition of these weapons by the United States in the 2018 NPR reflected the concern that the ROK has
regarding US extended deterrence. The ROK continues to build its conventional defensive capabilities. Although“nuclear sharing,” referring to US extended deterrence, is an effective approach, it does not really constitute“sharing” of nuclear weapons between the United States and the ROK due to the nature of the US nuclear
command and control system. To clarify this relationship in the 2018 NPR, “nuclear sharing” was deleted andreplaced by “burden sharing.”
40

Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA), Project Year 1

16about their actual use in a retaliation-required situation. 45 Therefore, possessing nuclear weaponsof various yield and capabilities can fill the void in nuclear power, enable flexible responses, andenhance the will-to-execute and credibility of extended deterrence.
There are also problems, however, in continuously strengthening nuclear deterrence on the
Korean Peninsula. The more aggressive the nuclear posture, the greater the possibility of using
nuclear weapons due to uncertainty about the intentions of the other party. In addition,
strengthening nuclear deterrence may lead to an intensifying arms race between hostile countries,
such as in development and deployment of nuclear weapons and missile defense systems. In
particular, since the DPRK insists on possessing nuclear weapons to ensure its survival under the
threat it perceives from US nuclear weapons, strengthening US nuclear deterrence may have anegative impact on the progress of denuclearization on the Korean Peninsula. Therefore, it is also
necessary to consider balancing the goals of strengthening nuclear deterrence and creating apeaceful security environment on the Korean Peninsula.

V. Conclusion
In this paper, several nuclear use cases were investigated based on the DPRK's nuclear
capabilities and nuclear strategy. The fact that the DPRK has maintained an offensive military
strategy for a long time and has recently announced its tactical nuclear development programshows that it is highly likely to adopt an offensive nuclear strategy in the future. Due to thepresence of such a strategy, the possibility of using nuclear weapons is expected to increase, andthe possibility of a direct attack on the ROK Army Mobile Corps and/or an EMP attack on Seoul
and Busan might also be expected to be high. To prevent those nuclear use cases from becoming
reality, the credibility and effectiveness of the United States’ extended deterrence should be
strengthened in its political and military aspects.
Recently, the DPRK has been taking a double stance, in which while they have restored interKorean military leadership communication lines, 46 Kim Yo-Jong has publicly demanded thesuspension of US-ROK joint exercises 47 and the withdrawal of US troops from Korea. 48
Therefore, although there are inevitably trade-offs with goals such as the establishment of peaceon the Korean Peninsula, strengthening security cooperation within the US-ROK alliance isWhen considering planning/employment as well as deterrence of nuclear weapons, it would be natural for the
ROK to actively participate in the nuclear planning/employment program on the Korean Peninsula (which is Korean
territory) with the United States, given the ROK/United States alliance. The point here is that the withdrawal of US
nuclear weapons from the ROK has raised some doubts in the ROK about US extended deterrence because the lackof the physical presence of nuclear weapons in the ROK appears to further remove decisions about nuclear forcesfrom ROK involvement.
46
Yonhap News, “Restoration of inter-Korean military communication lines,” July 27, 2021.
47
Yonhap News, “Kim Yo-jong, ‘ROK-US military exercises obscure the future of inter-Korean relations... Watch theSouth Korea's decision,’” August 1, 2021.
48
Joongang News, Kim Yeo-jung's first request for "withdrawal of U.S. troops"... Difficulties in denuclearization
negotiations rise again,” August 11, 2021.
45

Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA), Project Year 1

17needed in the current situation where progress on the denuclearization of the DPRK is notachieved and is delayed.

Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA), Project Year 1

18