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Citation: Japan and the World, Japan Digital Library (March 2017),
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The North Korean Nuclear Issue andJapan’s Deterrence Posture*
Hirofumi Tosaki(The Japan Institute of International Affairs)
Introduction
After Pyongyang’s violation and subsequently abandonment of the US-North Korean “Leap Day Deal” inFebruary 2012 by the North’s test-flight of its long-range ballistic missile under the guise of launching asatellite for “peaceful” purposes, few clues for resolving the North Korean nuclear issue have been found.
Since the first nuclear crisis in the early 1990s, Japan, the United States and South Korea have sought a
diplomatic solution to this issue, through a policy of “engagement and pressure.” However, North Korea,
which has continued to develop nuclear weapons capabilities, has repeatedly reneged on pledges relating
to dismantlement of its nuclear weapons program, inter alia, the US-North Korean Agreed Framework
in 1994 and the Joint Statement of the Fourth Round of the Six-Party Talks with its Initial and SecondPhased Actions for Implementation agreed in 2005 and 2007. Furthermore, Pyongyang has repeatedly
trumpeted its possession and reinforcement of nuclear deterrent capabilities. For instance, North Korea
adopted the “Law on Consolidating Position of Self-Defensive Nuclear Weapons State”1 in April 2013; inOctober 2015 First Secretary (at that time) Kim Jong-un stated, “We must turn out powerful cutting-edge
military hardware of our own style in larger numbers, constantly reinforce self-defensive nuclear deterrent and perfect the preparedness for an all-people resistance”;2 and the North conducted its fourth nuclear test on January 6, 2016, and another “satellite launch” on the following February 7.
A country’s acquiescence to give up its strong determination to acquire nuclear weapons has often
been associated with a change of its regime (at least in character). The North’s denuclearization mightalso need to follow the same pattern. However, any attempts to overthrow the Kim dynasty from outside
would pose a tremendous risk, and regime change from inside seems unlikely at this moment. Needlessto say, given the possibility of a fierce counterattack by North Korea, a disarming strike against that country would not be an easily achievable option. In the current situation, where any efforts to resolve theNorth Korean nuclear issue are facing serious deadlock and North Korea is all the while continuing todevelop nuclear weapons and ballistic missiles, what Tokyo, Washington and Seoul could pursue is—asmeasures for “containment and crisis management” while “engagement and pressure” have notnecessarily worked as expected—to reinforce their deterrence postures (respectively and/or collectively)* This article was originally published as Hirofumi Tosaki “Kitachosen no Kakumondai to Nihon no Yokushitaisei: Genjo to

Kadai” in the Japan Institute of International Affairsʼ Report on the Korean Peninsula (March 2016), Chapter 13, 139-155,
http://www2.jiia.or.jp/pdf/research/H27_Korean_Peninsula/13-tosaki.pdf

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against the North’s use of, or threat to use, nuclear weapons.
In that sense, from the establishing of the “National Security Strategy” (December 2013) and the
Cabinet Decision on “Development of Seamless Security Legislation to Ensure Japan’s Survival andProtect its People” (July 2014), to the revision of the “Guidelines for Japan-U.S. Defense Cooperation”(April 2015) and the enactment of the Japan’s Legislation for Peace and Security (September 2015), theimplications of Japan’s security policy reforms are significant. Since the end of the Cold War, in order tobe able to respond to a variety of events that cause changes in the international and regional security
situation, Japan has reformed and revised its security policy in a gradual or patchwork manner. Against
this backdrop, the North Korean nuclear issue has been one of the most important factors, leading to,inter alia, the enactment of the “Act on Measures to Ensure the Peace and Security of Japan in Perilous
Situations in Areas Surrounding Japan” and contingency legislation, as well as various decisions relating
to ballistic missile defense (BMD). Since the start of 2010s, because of diversifying security risks thatJapan has been facing, including rising China’s provocations possibly aiming to revising regional andinternational orders, the importance of North Korean issues in Japan’s security has been relativized.
Nevertheless, at least in the short term, North Korea remains the country that poses the most serious anddestructive threat to Japan. Therefore, the North’s nuclear issue was included as one of the important
items for contemplating Japan’s security policy reforms from 2013 to 2015, whose main purposes are toconstruct a security system that bridges seamlessly from peacetime to military contingency, establish a
policy framework tailored to the emerging security environment, and comprehensively reorganize thelegal and political distortions that arose from post-Cold War gradualism.3
The challenge that Tokyo needs to address subsequently is to embody those reforms in a way that
actually bolsters Japan’s deterrence posture. However, it is by no means an easy task to construct an effective deterrence posture against North Korea. Furthermore, it needs to be taken into account the paradoxthat strengthening the deterrence posture might create additional instability for Japan’s security. This
paper will focus on Japan’s deterrence posture vis-à-vis a North Korea that has been increasing its nuclear
and missile capabilities, and discuss the challenges of maintaining and strengthening this posture from theperspectives of, firstly, opacity, uncertainty and fluidity regarding North Korea’s deterrence posture; secondly, the possibility of escalation of a conflict to a nuclear level as a result of the stability-instability paradox; and thirdly, the constraints and limitations that pertain to Japan’s capabilities and policies.

1. North Korea’s capability, intention and perception
The basic requirements for a deterrent to work are for a deterrer to have the “capability” and “intention”
to inflict cost and risk upon a deterree that outweigh benefits of any unacceptable actions, and for thedeterree to be “perceived” such a situation. In addition, in order to construct an effective deterrence posture, it is necessary for the deterrer to understand, to as high a degree as possible, the deterree’s “capability,” “intention” and “perception.”4 In any case, a perfect understanding of these elements could not be
expected, and in the case of North Korea in particular, “capability,” “intention” and “perception” arehighly opaque, uncertain and fluid. This is one of the important factors that makes it very difficult toconstruct an effective deterrence posture against North Korea.

(1) Nuclear and missile capabilities
North Korea’s nuclear forces could present an actual threat to Japan’s security over a wide spectrum, frompeacetime to military contingency. The aspect and severity of the threat is defined by North Korea’s nuclear weapons capability, nuclear strategy and policy, and by developments such as that country’s domestic
and foreign political and security situations. Among them, the most important variables is the North’s
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“capability.” While Pyongyang certainly possesses at least nuclear explosive devices, as evidenced by its
four consecutive nuclear tests, the actual extent of its nuclear weapons capability is not necessarily clear.
With regard to the numerical aspect, because of a lack of accurate information on the amount offissile material for nuclear weapons that North Korea has produced and will be able to produce, there arevarious estimates on the number of its current and future nuclear weapons. For example, the StockholmInternational Peace Research Institute (SIPRI), based on the estimated amount of weapons-grade plutonium that the North has produced, estimated the number of its nuclear weapons at the end of 2014 to be
between six to eight.5 On the other hand, David Albright, adding in factors such as the number of North
Korean uranium enrichment plants and the number and capability of centrifuges and their operational
status, estimated the number of nuclear weapons to be either 10 or 11, or around 15 to 16.6
The pace of increase in the number of nuclear weapons will be significantly affected by the capacity
to produce weapons-grade fissile material. Given that the 5MW graphite-moderated nuclear reactors
used in the production of plutonium has operated sporadically,7 and that a 50MW experimental lightwater reactor has long been under construction, of immediate serious concern is the trend of uranium
enrichment activity. The uranium enrichment facility to which North Korea invited US scientists in
November 2010 was installed with around 2,000 centrifuges.8 The existence of other, clandestine facilities
has been indicated, and in August 2015, Pyongyang reportedly commenced operational tests of a second
uranium enrichment facility.9 However, enrichment plants can be built underground and the number ofplants, and the number and capacity of the centrifuges, as well as their operational status are not hard toconceal, making it difficult to form an accurate estimate. With four million tons of uranium mine reserves (estimated), North Korea has seemed to expand its uranium enrichment capability at a rapid ratesince 2013, including enhancing its capacity to mine and mill natural uranium.10 Based upon various
estimates, Joel S. Wit and Sun Young Ahn predicted possible three scenarios on how many nuclear warheads North Korea could produce by 2020: the first is that it will possess approximately 20 warheads; thesecond is it will produce 50 warheads; and the third is a “worst case” scenario in which the number ofnuclear warheads increases rapidly to 100, and North Korea becomes able to deploy both tactical andstrategic nuclear weapons because of drastic advances in design technology. They concluded that thesecond scenario is the most likely.11
In addition to the numerical aspect, the qualitative aspect of nuclear development is also of serious
concern. In its announcement made immediately after the fourth nuclear test, North Korea claimed that“[t]hrough the test conducted with indigenous wisdom, technology and efforts the DPRK fully provedthat the technological specifications of the newly developed H-bomb for the purpose of test were accurate and scientifically verified the power of smaller H-bomb.”12 However, judging from the magnitude of
the artificial seismic event detected by the International Monitoring System of the Comprehensive
Nuclear-Test-Ban Treaty (CTBT), the estimated yield of this nuclear explosion was around 6.0 kilotons(that of the third nuclear test was 7.9 kilotons), the North’s claim of using a “hydrogen bomb” was widely
doubted. Nevertheless, it has been pointed out that Pyongyang attempted to test a boosted fission
weapon,13 or of components of a hydrogen bomb.14 While the details of the fourth test are as yet unclear,
it must be considered that North Korea could make some qualitative improvement on its nuclear weapons capability through the test.
One of the grave concerns to Japan’s security is that North Korea achieves the capability to miniaturize nuclear warheads and mount them onto its ballistic missiles. A spokesman for the Policy
Department of North Korea’s National Defense Commission stated that “It is long since North Korea’s
nuclear striking means have entered the stage of producing smaller nukes and diversifying them,”15,
which strongly suggested that they possess such capability. It is likely that North Korea, which has been3

developing nuclear weapons for more than 20 years, already possesses nuclear warheads that can bemounted on the Nodong road-mobile medium-range ballistic missile (MRBM), which is capable ofstriking Japan’s entire territory.16 While some officials in the US and South Korean governments view theNorth’s nuclear capability cautiously,17 South Korea’s 2014 Defense White Paper points out that the miniaturization of nuclear warheads “has reached a considerable level,” and General Curtis Scaparrotti, commander of the US forces in South Korea, also commented in October 2014 that “I believe [North Korea
has] the capability to miniaturize a device at this point, and they have the technology to actually deliver
what they say they have.”18 In addition, Japan, in its 2015 Defense White Paper, stated: “Over eight years
have already passed since North Korea conducted its first nuclear test in October 2006. North Korea has
conducted three nuclear tests to date. North Korea’s duration of technology development and the numberof tests are reaching levels that cannot be said to be inadequate in comparison with the processes of developing technologies to miniaturize and lighten nuclear weapons in the United States, Soviet Union,
United Kingdom, France, and China”.19 After the North’s fourth nuclear test on January 19, 2016, according to its 2016 Defense White Paper, Tokyo contemplated that “[t]aking into account that North Korea
has not changed its stance of continuing passage of time, there would be a greater risk of North Korea
deploying a ballistic missile mounted with a nuclear warhead that includes Japan in its range.”20
As for the North Korean ballistic missiles capabilities21 whose exact figures and operational statushave not been released, it is widely considered that Pyongyang possesses more than 200 missiles andapproximately 50 mobile launchers, with a certain level of invulnerability and combat readiness. North
Korea has also aggressively pursued development of ballistic missiles capable of reaching US territory.
The Musudan mobile intermediate-range ballistic missile (IRBM), developed based on the Russian R-27
submarine-launched ballistic missile (SLBM), is considered to have the ability to reach Guam. In addition, the fixed ICBM Taepodong 2, launched as the space launch vehicle (SLV) named “Unha 3” inFebruary 2016, is believed to be capable of reaching the US mainland and, albeit its low reliability, it has
been analyzed as having emergency operational capability.22 Regarding the road-mobile ICBM KN-08s,
in April 2015, Admiral Bill Gortney, then commander of North American Aerospace Defense Command(NORAD), indicated that they had already been deployed.23 Furthermore, North Korea has also embarked on the development of an SLBM “Bukgeukseong” and has conducted repeated ejection tests since
May 2015. South Korean military officials have reportedly said that the North will be ready to deploy a
new submarine that can carry SLBM in as soon as two to three years, and will have developed the missile
in four to five years.24 North Korea’s ICBM and SLBM capability is likely to be rudimentary and highly
vulnerable, but if continued development and testing enable them to develop practical and invulnerable
capabilities to attack the US homeland, this could well have considerable implications for the reliabilityof the extended deterrence that the United States has provided Japan.
The actual situation with regard to the both quantitative and qualitative capabilities of North Korea’s
nuclear weapons and ballistic missiles, as well as the figure and pace of their development, is not necessarily able to be ascertained accurately, leaving the deterrers in the difficult position of having to develop
their deterrence posture, in consideration of the range of possibilities.

(2) Intention
In the consideration of developing and strengthening of a deterrent posture, a deterrer faces difficulty inapprehending correctly whether the purposes behind North Korea’s acquiring and bolstering of its nuclear arsenal, as well as its “intention” on use of nuclear weapons, are defensive—such as for the survivalof its regime—or aggressive—including for the unification of the Korean Peninsula by the North, orachievement of more limited objectives.25 Moreover, it could be more complicated due to a possibility
4that the North’s purpose or intention would change at short notice.26
North Korea has consistently maintained that the possession of a “nuclear deterrent power” is adefensive measure for the purposes of deterring US and South Korean attacks, and ensuring the regime
survival. The abovementioned “Law on Consolidating Position of Nuclear Weapons State” stipulates:“The nuclear weapons of the DPRK are just means for defense as it was compelled to have access to themto cope with the ever-escalating hostile policy of the US and nuclear threat,” and “They serve the purposeof deterring and repelling the aggression and attack of the enemy against the DPRK and dealing deadly
retaliatory blows at the strongholds of aggression until the world is denuclearized.”27
It is reasonable to consider that the North’s nuclear strategy is defensive in nature at least at thismoment should its ability to conduct nuclear strike (particularly vis-à-vis the United States) is extremely
limited, which could be just served as existential deterrence—imposing cautious behaviors on a deterreeby the fact of possessing nuclear weapons. However, this does not mean a “weakness” of its deterrence. If
Pyongyang judges that its vital interest, in particular a survival of its regime, is seriously at risk in a contingency on the Korean Peninsula, it could reach a strong determination to use nuclear weapons. In
contrast, US national interest in the Korean Peninsula is not necessarily as “vital” as that of the North.
Such an “asymmetry of interest” could result in an “asymmetry of determination” with regard to the useof nuclear weapons, and that, as a result, the United States might end up being deterred by North Korea.
In addition, North Korea is likely to expect that its nuclear deterrent would work as an “equalizer” forcomplementing its overwhelmingly inferior conventional forces, compared to those possessed by theUnited States and South Korea.
On the other hand, it should not be ruled out as a possibility that North Korea intends to use nuclear
weapons offensively for achieving unification of the Korean Peninsula, or other limited objectives. The
latter cases have already become a reality in the form of the “stability-instability paradox.”28 The “stability-instability paradox,” in the context of the North Korean issue, means that North Korea’s possession of
nuclear strike capability (particularly against the United States) leads the North to have confidence thata certain level of stability has been created in terms of a “higher end” deterrence relationship; therefore,
North Korea may consider that it could safely decrease a threshold conducting a limited provocation ina “lower end” contingency or conflict, thus increasing instability. It has been analyzed that, behind North
Korea’s torpedo sinking of the South Korean corvette Cheonan in March 2010, and its artillery shelling of
Yeonpyeong Island in the following November, Pyongyang may have considered these provocations effective in shifting the main axis of dialogues among countries concerned to the US-North Korean one,and urged the United States to resume bilateral talks.29 At the same time, from the “stability-instability
paradox” perspective, it can be posited from these contingencies that Pyongyang’s self-confidence in“strengthening of the nuclear deterrent” after the second nuclear test in May 2009, as well as its calculations of the US and South Korean perceptions regarding North Korea’s possession of nuclear weapons,
influenced the process of decision-making to take such provocative military activities. The concern isthat, as North Korea’s nuclear strike capability, particularly against the United States, strengthens, thethreshold of a military provocation in a lower-end contingency may decrease, the intensity of such provocation may increase; and North Korea’s objectives may rise to a level that Tokyo, Washington and Seoul
could no longer accept.
On the other hand, Robert Carlin and Robert Jervis argue that North Korea’s provocations are notdue to the “stability-instability paradox,” but could be considered to stem rather from the dynamics ofNorth Korea’s internal affairs.30 Ken Watman et al. also point out that regional hostile states in which
the stability of their regimes is threatened by their internal political affairs, besides a threat from outside, are likely willing to take (or even create) risks for diverting attention to avoid increasing domestic
5

objections against their regimes; therefore, they tend to embark upon military actions, whether their
purpose be offensive or defensive.31 North Korea’s intentions of provocations cannot always be accurately apprehended.
The purposes of Pyongyang’s options to use nuclear weapons are also difficult to accurately understand for outside actors. While North Korea’s nuclear posture is not necessarily clear, one of the possibilities is to bring an end to a contingency in its term and before the collapse of its regime by denying a US/
South Korean attempt to escalate (that is, de-escalation) or by forcing China to intervene in the contingency through a threat of using nuclear weapons, or their limited and/or demonstrative use. Such a nuclear posture could be applicable for either defensive or offensive purposes.
Moreover, in the initial phase of acquiring nuclear weapons, there are significant fluctuations in thequantitative and qualitative capabilities of the nuclear arsenal, including delivery vehicles. Under such asituation, while the motivation of a country to acquire nuclear weapons first of all defines components of
its nuclear arsenal, what it achieves in nuclear capability development may bring about changes in the
purpose of possessing nuclear weapons, or in its nuclear employment policy. The extent to which a deterrer could accurately apprehend changes in the deterree’s intention would significantly affect the success or
failure of deterrence. However, with additional factors of opacity and uncertainty as well as that of fluidity
regarding the North’s capability and intention, Japanese, US and South Korean strategic calculations
should be more complicated, which would make establishment and adjustment of their deterrence posturemore difficult. This means that a possibility and risk of deterrence failure may also increase.
For example, even if Pyongyang’s nuclear strategy is directed by its defensive purpose, Tokyo,
Washington and Seoul might misperceive the North’s Korea’s intention in an analysis based on inadequate or inaccurate information, and would adopt a more aggressive deterrence posture than needed.
Then, should North Korea misperceive that their objectives in bolstering deterrence posture are preemption or regime change, increasing its threat perception unnecessarily, it might strengthen its nuclear arsenal or take offensive actions for countering vulnerability. In order to lessen the risk of deterrence failurethat may be caused by this kind of security dilemma and encourage North Korea to act in accordancewith the deterrers’ intention, it is vital to provide North Korea with a certain level of reassurance andsecurity guarantee, besides deterring it.32 On the contrary, if those three countries (over)emphasize thereassurance to a North Korea whose purposes of possessing and strengthening nuclear and missile capabilities are to achieve more aggressive objectives, the latter might perceive their behaviors as a sign of“weakness,” and an opportunity to embark upon aggressive actions for achieving its objectives.
In a highly unclear, uncertain and fluid situation regarding the deterree’s capability and intention, it
is no easy task to strike a suitable balance between deterrence and reassurance. Furthermore, constructing and strengthening a deterrence posture under such a circumstances inevitably contains some factorsthat could bring into a failure of deterrence. Moreover, there is a significant possibility that misunderstanding and suspicion of each other could be amplified by taken “rational” practices in deterrence posture, such as: North Korea maintains opacity regarding its capability and intention for enhancing aneffectiveness of its deterrence, on the one hand; and Japan, the United States and South Korea constructtheir deterrence posture with assuming even a worst case scenario, on the other hand.
In addition, communication between North Korea and other three countries on strategic issues isdecisively lacking, meaning that they would force to take strategic responses under conditions wheremutual perceptions on their deterrence posture, respectively, are extremely poor.33 Risks of destabilizing
deterrence relationship and failing deterrence are further increased by misunderstanding and miscalculation due to recognition bias as a result from, for instance, shutting out of inconvenient information, or(often mistakenly) positing from historical analogies.34
6

2. Possibility of escalation to nuclear level
The structural challenges of the deterrence relationship, mentioned above, pose difficulties to Japan, theUnited States and South Korea in that the interactions of rational decisions made by each party mightbring forth an irrational consequence in the form of North Korean escalation of a conflict to a nuclear
level as well as a risk of failure of deterrence. In particular, during a transitional period when the North
increases nuclear and missile capabilities for establishing a reliable deterrence posture, instability in thedeterrence relationship would grow. Furthermore, with regard to developments since 2010, the possibility of a nuclear escalation by Pyongyang seems to increase due to a parallel build-up of asymmetric deterrence postures, in which: North Korea has bolstered nuclear and missile capabilities; and Japan, theUnited States and South Korea, concerned about North Korea’s aggressive behaviors, strengthen conventional deterrence.
Against this backdrop, the focus of South Korea, and the US-South Korea alliance, has been thereconstruction of their deterrence posture in order to alleviate the “stability-instability paradox” in thewake of the North Korean military provocations in 2010 mentioned above. If they could have not taken
an appropriate response against North Korea’s provocations—aimed at, for instance, achieving fait accompli, probing, forcing its will on them, and demonstrating its power to and tightening its grip on thedomestic audience—Pyongyang may have interpreted that as tolerance of and acquiescence to those actions, which would have led to repeated and increased provocations. Therefore, reconstruction of theirdeterrence postures was a proper response.
Immediately after the Cheonan incident, Seoul announced a “proactive deterrence” in May 2010, in
which North Korean provocations would be not tolerated, and would be defeated by serious retaliation.
In 2012, South Korea announced its plan to build a “Kill Chain” for detecting signs of an impending
attack by North Korean nuclear forces, missiles and long-range artillery, and to destroy them preemptively. The system would comprise multi-purpose satellites, high-altitude unmanned surveillance aircraft, ballistic and cruise missiles,35 and Korean Air and Missile Defense (KAMD). Furthermore, in the“National Defense Reform Basic Plan (2014 to 2030)” issued in March 2014, South Korea declared thatits core military strategy would be “active deterrence,” under which the South attempts to effectively deterNorth Korea’s diverse threats and to decisively cope with its provocations at the level of the right ofself-defense.36 In September 2015, in an attachment to an operating report submitted to the National
Assembly audit by the National Defense Committee, the Army Special Operation Warfare Command
reportedly addressed that it has promoted to form a special operation unit for striking the enemy’s “strategic core targets,” which mean “military facilities with a strategic significance, such as those for nuclear
weapons and long-range missile.”37
Meanwhile, the US-South Korea alliance had already included plans for precision strikes against
North Korea’s nuclear facilities in the Operational Plan (OPLAN) 5026, formulated in the early 1990s.
In March 2013, the “U.S.-ROK Counter Provocation Plan” was adopted to cope with local attacks by
the North’s conventional forces. At the US-South Korean Security Consultative Meeting in October
2014, the “Concept and Principles of ROK-U.S. Alliance Comprehensive Counter-missile Operation”
was concluded, laying out the 4D (Detect, Defend, Disrupt and Destroy) policy against North Korean
missile attacks.38
The “test case” for their deterrence postures mentioned above came with the South-North clash in
August 2015. In retaliation for the wounding of two South Korean soldiers by land mines that appear tohave been laid by North Korea in the demilitarized zone in South Korean territory, the South Korean
armed forces resumed propaganda broadcasts against the North for the first time in 11 years. North
7

Korea responded by firing one round from an anti-aircraft gun and several rounds from a 76.2 mm fieldgun. In addition, the General Staff Department of the North Korean Army sent notification to the Southto the effect that “unless the psychological warfare broadcasts against North Korea stop within 48 hours
from 17:00 on the 20th, military action will commence.”39 North Korea reportedly declared a semi-stateof war to its front line divisions, moved artillery units to the front line, deployed mobile launch vehicles
carrying Nodong MRBMs and Scud short-range ballistic missiles (SRBMs), and put to sea around 50
submarines. South Korea, in response to the shelling by North Korea, fired several dozen 155 mm rounds
into North Korean territory in the demilitarized zone, and President Park Geun-hye ordered high-ranking officials of the armed forces to “respond firmly” to North Korean provocation. However, even after
the “48 hours” North Korea did not embark upon any military actions. On August 23, a meeting among
high-ranking North and South Korean officials was held at Panmunjom, and the contingency came to an
end with the release of the “Joint Press Release from the Inter-Korean High-Level Meeting.”40
In this crisis situation, if North Korea had planed further military provocation for some offensive
objectives, it could be concluded that the South Korean and the bilateral alliance’s deterrence postures haveworked to a certain extent, in the sense that there was no additional escalatory military action, apart fromthe North’s initial firing of a few rounds. However, there is no guarantee that their deterrence will work inthe same way in the future contingencies. As mentioned above, should Pyongyang bolster its nuclear andmissile capabilities and has confidence in its deterrence at a higher-end conflict, it would attempt toachieve its objectives by limited provocations at a lower-end contingency, or re-retaliation in response toretaliation by South Korea or the US-South Korean alliance.41 Or, the North might re-retaliate for a defensive purpose of ensuring survival, with interpreting the US and South Korean retaliation as an attempt tochange North Korean regime. In either case, if South Korea or the US-South Korean alliance, facing thethreat of North Korean re-retaliation, continues military action for the purposes of repelling attacks and/or re-establishing the deterrence, the situation might deteriorate from a retaliation/re-retaliation spiral, to
one where the scale and intensity of the conflict exceed initial expectations.
Beyond such retaliation/re-retaliation, two scenarios can be considered in nuclear escalation. Firstis the possibility that, in the process of the expansion of the scale of the conflict, North Korea—fearing a
possibility of an attack by South Korea and/or the United States against the North’s nuclear and missile
capability, command and control systems, or its leadership—might decide to use its nuclear and missile
capability before destruction,42 or that the North Korean leadership seriously contemplate to conduct anearly use of nuclear weapons if an attack on the command and control system makes it difficult for the
North to fully comprehend the situation, or make them judge an attack against the regime. The second
possibility is that North Korea would attempt a nuclear escalation for preventing US intervention in acontingency on the Korean Peninsula and bringing an armed conflict to an end in a form that is favorable
to them. It should be noted that Pyongyang would decide on nuclear escalation at an early stage of aconflict or in one leap. Practically the one of few North Korean asymmetrical escalatory capabilities
which could offset the overwhelming military superiority possessed by the United States and South
Korea is its nuclear and missile forces; therefore, it has few options but rely on those capabilities forachieving to deter them. Furthermore, North Korea may consider that the impact of the threat to use
nuclear weapons at an early stage could be a key for increasing a chance of success in deterring them.
Another point to be noted is that it may be Japan, rather than the United States or South Korea, thatwould be the first target of North Korea’s nuclear attacks. It is no doubt that Pyongyang’s first target interms of deterrence is the United States since preventing an US intervention in a contingency on the
Korean Peninsula should be vitally significant for the North. While the presence of the US forces in South
Korea is expected to conduce almost automatically the US intervention in a Korean Peninsula8contingency, what North Korea expects from the threat of a nuclear use vis-à-vis the United States is tomake Washington deter Seoul as well as itself for avoiding involvement: that is, to get the United States tostrongly request the South to refrain from any actions that might lead a situation into a military conflict,or to have the US forces act with extreme restraint in order not to provoke North Korea into choosing to
make a nuclear attack. However, North Korea’s ability to conduct a nuclear attack against the UnitedStates is, at least for the time being, very limited and rudimentary; just possessing and threatening to usethem would not be enough to deter the US intervention. Although North Korea may also have an optionof using S/MRBMs against US forces in South Korea, they do not have the accuracy enough to achievecounterforce operations; nor is it highly likely that the North would use nuclear weapons in the territoryof South Korea, where fellow Koreans reside.
Under such circumstances, a nuclear attack against Japan could be a more realistic option. Should acontingency on the Korean Peninsula escalate, Washington would need to send its troops stationed in the
US homeland and Japan. In this case, the US bases in Japan and the Japan Self-Defense Forces (SDF)
bases would be utilized as hubs for sending the troops to South Korea, and Japan would be expected tosupport these operations. In addition, as a result of the recent security policy reforms, among others,
Japan’s role in logistical or rear area support has been expanded; and the government modified the interpretation of Article 9 of Japan’s Constitution to permit the exercise of the right of collective self-defense,
albeit in a strictly limited manner. These reforms certainly increase Japan’s role in the defense of South
Korea in the event of a contingency on the Korean Peninsula. At the same time, however, these developments contain the paradox that, as a side effect of bolstering deterrence posture, North Korea would
consider a nuclear attack or its threat vis-à-vis Japan more significant.
If a contingency on the Korean Peninsula were to escalate and become identified as a “situation thatwill have an important influence on Japan’s peace and security,” Tokyo would conduct operations underthe “Act on the Peace and Independence of Japan and Maintenance of the Nation and the People’s Security
in Armed Attack Situations etc. and Situations Where an Armed Attack against a Foreign Country Resultsin Threatening Japan’s Survival.” which provides for logistical support for a wider range of countries,
contents and regions than the “Law Concerning Measures to Ensure the Peace and Security of Japan in
Situations in Areas Surrounding Japan” in 1999.” Such operations include, for instance, rear area supportand search and rescue activities for the US troops that conduct operations contributing to the achievement of the objectives of the Japan-US Security Treaty, and other foreign military troops that conduct
operations contributing the achievement of the objectives of the UN Charter. In addition, under the new“Guidelines for Japan-U.S. Defense Cooperation,” the “Responses to Emerging Threats to Japan’s Peaceand Security” cover operations for noncombatant evacuation, maritime security, measures to deal withrefugees, search and rescue, protection of facilities and areas, logistic support, and use of facilities.
If an armed conflict on the Korean Peninsula were to escalate, Japan would identify it as “certain
situation, an armed attack against a foreign country could threaten Japan’s survival,” which means “whenan armed attack against Japan occurs or when an armed attack against a foreign country that is in a close
relationship with Japan occurs and as a result threatens Japan’s survival and poses a clear danger to fundamentally overturn people’s right to life, liberty and pursuit of happiness”. (If the armed attack were directly against Japan, this would be an “armed attack situation.”) The “Three New Conditions for ‘Use ofForce’ as Measures for Self-Defense,”43 adopted by the Cabinet in July 2014, mentions a new interpretation that the Constitution permits not only individual self-defense, but also collective self-defense, withstrict limitations on its exercise. According to this reinterpretation, if a contingency or armed conflict on
the Korean Peninsula is identified as the “situation threatening Japan’s survival,” in accordance with theArmed Attack Situations Response Act and the Self-Defense Forces Act, Japan can conduct operations
9for, inter alia, interception of ballistic missiles aiming targeting the United States, “assets protection” toprotect US ships engaging in BMD operations or evacuation of Japanese people, minesweeping; andcombat search and rescue.
Considering the probability that North Korean use of, or threat to use, nuclear weapons would
occur as a result of an escalation of armed clash, Japan’s roles and efforts mentioned above are to contribute in complementing the reinforcement of deterrent postures led by the United States and South Korea,
for deterring North Korea from conducting military actions at an even much lower level, maintaining
escalation superiority against the North Korea at each stage of an armed conflict, and developing a posture that adequately denies any North Korean attempt at asymmetric escalation. In particular, should
Japan’s efforts result in an improvement in US damage limitation, then the possibility that the UnitedStates will be deterred will be lessened, and the reliability of the extended deterrence that the UnitedStates provides Japan (and South Korea) will be further improved.
At the same time, therefore, it could be considered that Pyongyang would have a strong incentive todecouple Tokyo from Washington and Seoul, and to prevent any Japanese involvement in a contingency
on the Korean Peninsula. One of North Korea’s means for this would be a nuclear attack, or threat ofnuclear attack, against Japan. If, in the event of a contingency on the Korean Peninsula, the North is able
to compel Tokyo to refuse to permit US forces to use bases in Japan or provide rear area support for themor other countries’ forces, or not to exercise the right of collective self-defense, the situation could betilted favorably toward North Korea. A nuclear attack against Japan or threat of such an attack would also
demonstrate North Korea’s strong determination with regard to nuclear escalation to the United Statesand South Korea. Needless to say, Japan is under the US nuclear umbrella, but the possibility cannot be
excluded that North Korea might come to the conclusion that the United States is unlikely to conduct a
nuclear retaliation against the North’s nuclear attack on Japan, depending on the character of such a nuclear attack, or concerns over a nuclear re-retaliation against the United States.44 In addition, North Korea
might conclude that Japan, having experienced the atomic bombings of Hiroshima and Nagasaki, isvulnerable to the threat of nuclear attack, or that that it could justify the nuclear attack against Japan
under the guise of Japan’s pre-war colonial rule. It is no wonder that North Korea consider Japan a more
“appropriate” target for a nuclear attack than the United States and South Korea.
While less frequent than the nuclear threats made against the United States, North Korea has also
implied the threat of nuclear attacks against Japan. In March 2013, the North Korean Rodong Sinmun
carried an article that listed Okinawa along with the Andersen Air Force Base (Guam) as being within“the striking distance of the DPRK’s precision strike means.”45 The following month, it stated: “If theJapanese reactionaries join in the U.S. imperialists’ reckless moves for a war against the DPRK, failing toface up to the present situation, they are bound to meet a miserable end.”46 Furthermore, in July, theNorth referred to the possibility of an attack against Okinawa.47
Assuming that North Korea is a “rational” actor (in the light of Western standards), it would likely
be very cautious about the actual use of nuclear weapons, which would increase the probability of bringing down the end of the Kim dynasty. Whatever the reasons, however, if an armed conflict on the Korean
Peninsula escalates and the United States is highly likely to become fully involved in it, the meaning of
the conflict for North Korea would likely to transform into one where its vital interest of regime survival
would be seriously at stake. At this stage, the probability of its threat to use nuclear weapons would rapidly rise. In contrast, a contingency on the Korean Peninsula would not be directly linked to the Japaneseand US vital interests of national survival. This is part of the reason that the United States might be deterred from protecting Japan that is under the US extended deterrence, due to the asymmetry in interestand determination between the United States and North Korea.48
10Various options of nuclear attacks against Japan can be anticipated. For example, North Korea might
conduct very limited nuclear attacks on Japanese territory (excluding US military bases in Japan) or in thesea close to Japan, or conduct nuclear attacks on Japanese territory (excluding US military bases in Japan)
in a manner minimizing damage. The purpose of such attacks would be to demonstrate Pyongyang’s determination to escalate a conflict to the nuclear level, with the aim of compelling Japan to stop providing
support to the United States (and South Korea), or force Tokyo, Washington and Seoul to terminate thewar in terms favorable to the North. Similar outcomes would also likely result if North Korea were to detonate a nuclear weapon at a high altitude to generate an electromagnetic pulse (EMP). Unless its demands
were accepted, North Korea might further escalate the conflict by conducting additional nuclear attacks.
Needless to say, it is essential for Japan to make continuous efforts to develop an effective deterrence
posture based on its security policy reforms from 2013 to 2015, from the standpoint of responding toNorth Korea’s nuclear and missile threat. However, such effort alone will not linearly strengthen Japan’s
security. As has been mentioned, bolstering the deterrence posture may bring about a “paradox” of creating new instabilities and security challenges.
Assuming that there is little probability of a direct armed conflict breaking out between Japan andNorth Korea irrespective of the actions of any other countries, it is likely that a nuclear crisis that North
Korean poses to Japan would occur as the result of “dual involvements”—that is, Japan is involved in acontingency on the Korean Peninsula because of its alliance with the United States, which itself is involved because of the alliance with South Korea. Of course, Japan has the right to refuse to be involved in
the contingency to avoid an immediate risk. However, such an attitude would soon present Japan withthe dilemma of inviting US “abandonment” in a future contingency with which Japan would have tocontend. With Japan facing multiple, serious security risks that Japan could hardly address by itself, it is
no doubt that the significance of the Japan-US alliance is increasing. The question for Japan is how tofind the right balance between the strengthening the deterrence posture and avoiding the abovementioned “paradox” or “dilemma,” or how to manage such a difficult situation. As long as the North Korean
nuclear issue continues, Japan cannot avoid addressing these questions.

3. Challenges in Japan’s deterrence posture(1) Deterrence by denial
When contemplating the future of the Japan’s deterrence posture vis-à-vis North Korea, it is imperative
to take into account the current statuses and limitations of the policy and capacity aspects, in addition to
the abovementioned challenges. After the security policy reforms of 2013 to 2015, Tokyo reaffirmed its
basic deterrence posture that it continues to maintain and bolster a posture of deterrence by denial,49 andto rely on US extended deterrence as a form of deterrence by punishment.
Deterrence by denial—deterring an adversary by possessing capabilities for preventing and defeating its attack, and denying an achievement of its objectives—is generally more credible that deterrenceby punishment—through a threat of massive retaliation, deterring by imposing costs overwhelming
gains that an adversary expects—because a deterrer has less room for choosing to invoke military activities for denying than punishing.50 As argued above, the development of an effective deterrence postureagainst North Korea is no easy task. Therefore, the role of denial posture, which also functions as a capability for damage limitation in the event of deterrence failure, is significant for Japan’s security, particularly in this context.
In addition, strengthening Japan’s deterrence by denial contributes to improvement of the credibility of US extended deterrence. The important factors affecting the credibility of extended deterrence include the level of political relationships between the allies, as well as that of the damage limitation11

capabilities of the countries providing extended deterrence. If Japan is able to maintain and actually exercise security cooperation, including the exercise of the right to collective self-defense of the UnitedStates and others, despite North Korea’s coercion, by developing a denial posture, then the political relationship with the United States will be further solidified. Also, as Japan’s capabilities for deterrence bydenial complements damage limitation for the United States, the possibility that the invocation of US
expanded deterrence is deterred by North Korea decreases.
Furthermore, capabilities for deterrence by denial are also essential as a means of addressing the useof nuclear weapons in a situation where deterrence does not inherently work. For example, there is no
guarantee that the North Korean leadership knows its own nuclear and missile capability accurately—
under a dictatorship, exaggerated “successes” are likely reported to the leadership—and its false self-confidence might lead it to decide to use nuclear weapons. In addition, while North Korea’s actual management
and operation systems for its nuclear arsenal are not clear, as the number of nuclear forces increases at thevery least, the risk of the accidental or inadvertent use of nuclear weapons would increase. In a situationof tension, the possibility of unauthorized use cannot be ruled out. Were the North’s leadership become
desperate from the realization that its regime is close to demise, it might decide to launch nuclear attacks
to embroil other countries in a devastating situation. Moreover, in the event of internal instability within
North Korea, another risk would be that dissidents or a new administration seize control of nuclear
weapons and attempt to use them.
It goes without saying that bolstering Japan’s posture of deterrence by denial is extremely importantin responding to the North Korean nuclear issue. However, there also exist several challenges associatedwith this effort, which will be contemplated in the following sections, with the examples of ballistic missile defense (BMD) and counterforce operations.

(2) BMD
Under the current security policy and posture, the BMD is the only means for Japan to directly defend
itself against North Korea’s missile attacks. Although the intercept rate of the BMD cannot be perfect, the“value” of the threat of missile attacks is weakened, and Japan could decide to deny North Korea’s coercions if Japan possessed a highly capable BMD system. Strengthening the BMD capability that is still
under development continues to be very significant task for Japan.
Meanwhile, the first challenge is how to handle the mismatch between the offensive and defensivesides. The number of interceptors that Japan possesses, and the number that can be deployed in Northeast
Asia by Japan and the United States in the event of a crisis have not been declassified. Assuming that eightStandard Missile (SM)-3 Block IA interceptors for the Aegis BMD system are carried on one Aegis ship
and that Japan and the United States can deploy totally up to a maximum of 10 Aegis ships, then up to 80
interceptors can be launched. However, since North Korea has approximately 200 Nodong MRBMs, thenumerical gap between offensive and defensive capabilities is significant. North Korea does not have thatmany nuclear warheads. However, the BMD system cannot distinguish between nuclear and non-nuclear
warheads when intercepting, so the question of how to address a North Korean saturation attack using
Nodong missiles is a tremendous challenge. North Korea may also employ countermeasures against BMD,
including decoys and chaff. The continued both qualitative and quantitative improvement of intercept
capability, including the research, development and deployment of new BMD systems, is indispensable.
The second challenge is to cope with surprise missile attacks. Because a Nodong missile could reachJapan within seven to ten minutes of being fired, the latter needs to maintain an immediate interception
posture (quasi) permanently. However, the probability of a North Korea’s “out of the blue” ballistic missile
attack is low. Such a situation places a significant burden on the deployed units. To date, pursuant to12Article 82-3 of the Self-Defense Forces Act, Japan has publicly announced the “order to intercept” ballistic
missiles five times, and has issued a classified order once.51 All were done in response to North Koreanannouncements of “SLV” launches, or clear signs of imminent ballistic missile test launches. However,ballistic missiles are not always launched under the same circumstances. Therefore, it is essential to constantly monitor the movements of North Korea’s ballistic missile units, and to detect any extraordinary
activity at as early a stage as possible. Strengthening intelligence, surveillance and reconnaissance (ISR)
activities and capabilities is one of the top priorities for Japan and the Japan-US alliance.
The third challenge is the defense against ballistic missile attacks on the United States and its troops.
In a situation of “an armed attack against Japan(’s existence)” or of “an armed attack against a foreigncountry resulting in threatening Japan’s survival,” it is no doubt that interception of North Korean ballistic missiles aimed at US forces or territory, conducted by Japan or Japan-US alliance, will contribute toenhancing the Japan-US alliance as a whole, and the credibility of extended deterrence in particular. On
the other hand, Tokyo and Washington should contemplate how their interceptors are to be allocatedamong Japan and the US forces and territory, and how they can build a flexible BMD operational posture.
In addition, in a situation before an “an armed attack against Japan(’s existence),” according to Article82-3 of the Self-Defense Forces Act, it could be interpreted that Japan cannot intercept a ballistic missile
unless it is aimed at Japan52 while North Korea would conduct ballistic missile attacks on US troops or
territory in such a situation. In order to prevent cracks from occurring in the Japan-US alliance overJapan’s response to the North’s ballistic missile attacks, Japan and the United States should communicate
sufficiently on this issue, and contemplate, if needed, how to fill the gap of responding to attacks in thesequence of evolving a contingency on the Korean Peninsula.

(3) Counterforce operations
Since BMD cannot intercept ballistic missiles perfectly, it is imperative to develop a comprehensive andintegrated posture for alleviating a threat from North Korean nuclear and/or ballistic missile attacks,
which includes measures other than BMD.53 For instance, regarding passive defense, one of the important measures is to improve the resiliency of bases of the Self-Defense Forces and the US forces in Japan.
The new “Guidelines for Japan-U.S. Defense Cooperation” state: “In order to expand interoperability andimprove flexibility and resiliency of the Self-Defense Forces and the United States Armed Forces, the two
governments will enhance joint/shared use and cooperate in ensuring the security of facilities and areas.”
Regarding active defense, it has been discussed whether Japan should acquire a counterforce capability for striking military-related targets in an adversary’s territory. If one can, at least, reduce the numberof the opponent’s ballistic missiles by attacking them, their launchers or bases before launching, or byforcing the enemy to launch them under a certain pressure, this can be expected to minimize damage
caused by ballistic missile attacks, and produce a synergistic effect of a relative improvement in the BMD’s
intercept rate. Tokyo has interpreted that if the three conditions for the exercise of self-defense—an imminent and illegitimate act of aggression against Japan, no appropriate means to deal with such aggression other than by resorting to that right , and the use of armed force is confined to the minimum
necessary level—are met, attacks on enemy bases by Japan would be permitted under the Constitution.54
However, Japan does not possess much of the capabilities both qualitatively and quantitatively
which are needed to conduct counterforce operations in the opponent’s territory, such as a platform (ordelivery vehicle) which can reach and attack such targets; the assets to continuously monitor enemy’sbases and mobile launchers; and the networks to process and transmit information in real time. It would
take considerable time and expense for Japan to get to acquire its own counterforce capability for attacking the adversary’s ballistic missiles and its related assets. As Sugio Takahashi argues, it is not realistic to13

construct its own counterforce capabilities against a ballistic missile threats; rather Japan needs to consider what sorts of components for counterforce operations it should possess within its cooperation with
the United States under the bilateral alliance.55 Furthermore, it should also be taken into account that
South Korea would strongly oppose an attack by Japan on North Korean territory.
Therefore, at least for the foreseeable future, Japan will have no other options but to depend on
South Korea, which has been developing a “Kill Chain,” and the United States to attack North Korea’s
ballistic missiles, launchers, and related targets. That is why the extent to which the United States andSouth Korea can reduce the North’s missile threat should be an important concern for Japan. In particular, the issue directly affecting Japan’s security is how many US and South Korean forces and capabilities
would be allocated for addressing ballistic missile attack against Japan since their top priority must be toremove threats to themselves.
Another problem is that North Korea has endeavored to reduce the vulnerability of its ballistic missiles by, inter alia, expanding its arsenal of mobile ballistic missiles, and enhancing the resiliency of missile bases. This could raise the question of whether conventional forces are enough to disarm the North’s
ballistic missile capabilities. In the United States, some have strongly argued that: even with precision
strikes, the earth penetration and explosive capabilities of the US conventional forces are insufficient toeliminate the North’s missile threats; the United States needs low-yield and/or earth-penetrating nuclear
weapons; and possessing such capability results in bolstering deterrence against North Korea. Under the
Barack Obama administration, the United States adopted a policy not to develop any nuclear weapons
with new capabilities,56 but a new US administration, inaugurated in 2017, may consider a policy change
to acquire such capabilities and adopt a more aggressive nuclear posture. Strengthening the US nuclear
deterrence could contribute to Japan’s security, on the one hand, but increasing the role of nuclear weapons is a step that runs counter to nuclear arms control and disarmament, on the other hand. Tokyo
should contemplate carefully how to evolve a policy on counterforce in its overall foreign and security
policies, including nuclear arms control and nonproliferation.

(4) Trilateral consultation and cooperation
Japan alone cannot construct its own deterrence posture necessary to defend the country against theNorth Korean nuclear and missile threat. Japan relies on the United States for deterrence by punishment,
and needs, close cooperation of the United States and South Korea on deterrence by punishment. Albeit
no perfect deterrence, for deterring North Korea from using and threatening to use nuclear weapons asmuch as possible, it is essential for Tokyo, Washington and Seoul to collaborate in strengthening a deterrence posture against North Korea across the full spectrum from lower to higher end of a contingency;
and to maintain close security cooperation among three countries in peacetime as well.
Therefore, it is quite significant that the new “Guidelines for Japan-U.S. Defense Cooperation” statedthat “the two governments will establish a new, standing Alliance Coordination Mechanism, enhance
operational coordination, and strengthen bilateral planning.” In addition, security cooperation and close
communication with South Korea are also essential for coping with the North Korean problem. In a contingency on the Korean Peninsula, the US and South Korean response against North Korean nuclear andmissile forces would have vital implications for Japan’s security. It could also be pointed out that an offensive deterrence posture by South Korea carries the risk of provoking an unintended escalation of thecrisis. On the other hand, in the event of such a contingency, Japan’s involvement and cooperation under
the Japan-US alliance will play an important role for continuing to conduct operations by the US-South
Korea alliance. Trilateral security cooperation is imperative for both Tokyo and Seoul.
The three countries need to discuss more about, for instance, coordination in peacetime on
14

operational plans and their employment as well as establishment of a mechanism for coordination andliaison in a contingency regarding the BMD, as trilateral sharing of sensor information will contribute to
the improvement of their capabilities for intercepting ballistic missiles. While the Japan-South Korean
General Security of Military Information Agreement (GSOMIA) is expected to promote such information sharing, they have yet to conclude it.57 However, in December 2014, Japan, the United States andSouth Korea signed a memorandum of understanding concerning the sharing of defense information
related to North Korea’s nuclear missiles, enabling Japan and South Korea to share information via theUnited States.58 On January 22, 2016, after North Korea’s fourth nuclear test, South Korea is reportedly
close to deciding to connect its military information transmission system to the US military’s “Link 16”
system within 2016, by which the three countries will be able to share information in (near) real time.
Trilateral consultation by defense ministries and officials has been becoming closer. Such the trilateral
security cooperation should be a continuous one, not a temporary development in the wake of North
Korean nuclear and missile tests.59 Conclusion of a Japan-South Korea GSOMIA and an Acquisition and
Cross-Servicing Agreement (ACSA) should be the starting point of the trilateral close cooperation on
deterrence postures.

Conclusion
North Korea has entirely abandoned all agreements and pledges regarding its denuclearization, and has
continued to develop nuclear and missiles capabilities, including their repeated tests in 2016. Thereseems to be few clues towards resolving the North Korean nuclear issue; moreover, its nuclear and missile
developments have increased the threat to Japan, the United States and South Korea. Therefore, strengthening their effective deterrence postures, respectively and/or collectively, vis-à-vis North Korea has been
the top priority. The key for this effort is how they could ensure adaptability and flexibility for their deterrence posture since their development needs to be carried out with taking into consideration thepossibility of deterrence failure that could result from the opacity, uncertainty and fluidity of North
Korea’s capability, intention and perception. In the case of a nuclear escalation of a conflict, particularly
as a consequence of the “stability-instability paradox,” Japan might be the first target for the North’s use
or its threat of nuclear weapons. It is no doubt that Tokyo should strengthen its deterrence by denial inaccordance with its security policy, and trilateral, full-spectrum (from lower- to higher-end contingencies) deterrence posture against the North by further development and enhancement of the bilateral alliances and the trilateral security cooperation.
At the same time, the three countries have to grapple with the issue of what and how they should
send messages to North Korea. They have to repeatedly send a clear and strong message that neither
provocations by North Korea nor its nuclear escalation will be tolerated, and that any such actions will be
met with a serious response, along with activities underpinning those messages. It should also bear inmind, however, that such messages and activities might cause deterrence failure, contrary to their intentions. Bolstering their deterrence posture is extremely important; the problem is how to alleviate or prevent security dilemmas. The three countries need to make it clear that, while provocations by North
Korea will be defeated resolutely, the first option of Tokyo, Washington and Seoul is a diplomatic solutionof the North Korean issues, and that they have no intention of military attacks unless the North engages
in provocations. However, excessive reassurance for Pyongyang is also problematic because such an attitude might interpreted by the latter as appeasement, or be interpreted by states under US extended deterrence that Washington would decrease it defense commitments. It is vital to continuously adjust thebalance between deterrence and reassurance in accordance with changes in the situation, which is achallenge that cannot be avoided in the efforts for strengthening deterrence postures.
15(Written on February 24, 2016)

1.

“Law on Consolidating Position of Nuclear Weapons State Adopted,” KCNA, April 1, 2013, http://www.kcna.co.jp/
item/2013/201304/news01/20130401-25ee.html.

2.

Kim Jong Un, “The Cause of the Great Party of Comrades Kim II Sung and Kim Jong II Is Ever-Victorious,” KCNA, October
4, 2015, http://www.kcna.co.jp/item/2015/201510/news06/20151006-20ee.html.

3.

Ken Jimbo “Abe Seikenka de no Shimuresu na Anzen Hosho Taisei no Mosaku—Boei Keikaku no Taiko / Nichibei Boei
Kyoryoku no Gaidorain / Anzen Hosho Hosei” [In Search for Seamless Security Posture under the Abe Administration:
National Defense Program Guidelines, US-Japan Defense Cooperation Guidelines, and Security Legislation], Mondai to
Kenkyu [Issues and Studies], Vol. 44, No. 2 (April, May, June 2015), p. 34. (in Japanese)4.

In addition, if the foundation of deterrence is a deterree’s perception,” then in order to make it work properly, a high level ofknowledge is required with regard to, inter alia, the deterree’s objectives and strategies, its leader’s characteristics and preferences, decision-making processes, values and strategic culture.

5.

Stockholm International Peace Research Institute, SIPRI Yearbook 2015: Armaments, Disarmament and International
Security (Oxford: Oxford University Press, 2015), chapter 11.

6.

David Albright, “Future Directions in the DPRK’s Nuclear Weapons Program: Three Scenarios For 2020,” US-Korea
Institute at SAIS, 2015. According to his analysis, even if North Korea operates only one uranium enrichment plant, depending on the operational status, it may have been able to produce weapons-grade fissile material equivalent to 15 nuclear
weapons. Should it have two uranium enrichment plants, the North could have produced such material equivalent to 22
nuclear weapons. Regarding the number of nuclear weapons using weapons-grade plutonium, his estimate is the same asthat of the SIPRI, between six and eight.

7.

David Albright and Serena Kelleher-Vergantini, “Yongbyon: A Better Insight into the Status of the 5MWe Reactor,” Imagery
Brief, Institute for Science and International Security, April 29, 2015; William Mugford, “North Korea’s Yongbyon Nuclear
Facility: Sporadic Operations at the 5 MWe Reactor But Construction Elsewhere Moves Forward,“ 38 North, July 24, 2015,
http://38north.org/2015/07/yongbyon072415/.

8.

Siegfried S. Hecker, “Extraordinary Visits, Lessons Learned from Engaging with North Korea,” Nonproliferation Review, Vol.
18, No. 2 (July 2011), pp. 445-455.

9.

Jethro Mullen and Brian Todd, “New North Korean uranium enrichment hall likely up and running,” CNN, August 12,
2015, http://edition.cnn.com/2015/08/12/asia/north-korea-yongbyon-uranium-enrichment-report/.

10. Jeffrey Lewis, “Recent Imagery Suggests Increased Uranium Production in North Korea, Probably for Expanding Nuclear
Weapons Stockpile and Reactor Fuel,” 38 North, August 12, 2015, http://38north.org/2015/08/jlewis081215/; Mugford,“North Korea’s Yongbyon Nuclear Facility.”
11. Joel S. Wit and Sun Young Ahn, “North Korea’s Nuclear Futures Project: Technology and Strategy,” US-Korea Institute at
SAIS, February 2015. See also Albright, “Future Directions in the DPRK’s Nuclear Weapons Program.”
12. “DPRK Proves Successful in H-bomb Test,” KCNA, January 6, 2016, http://www.kcna.co.jp/item/2016/201601/news06/
20160106-12ee.html.
13. For an analysis that indicated a possibility of North Korea’s production of tritium which could be used in a boosted fission
weapons, see David Albright and Serena Kelleher-Vergantini, “Update on North Korea’s Yongbyon Nuclear Site,” Imagery
Brief, Institute for Science and International Security, September 15, 2015.
14. Barbara Starr, “North Korea May Have Tested Components of a Hydrogen Bomb,” CNN, January 29, 2016, http://edition.
cnn.com/2016/01/28/politics/north-korea-hydrogen-bomb-test/.
15. “Underwater Test-fire of Ballistic Missile Is Legitimate Exercise of Right to Self-defense: DPRK,” KCNA, May 20, 2015,
http://www.kcna.co.jp/item/2015/201505/news20/20150520-13ee.html.
16. See, for example, David Albright, “North Korean Miniaturization,” 38 North, February 13, 2013, http://38north.org/2013/02/
albright021313/.
17. “N. Korea Yet to Miniaturize Nukes: Seoul,” Korea Herald, February 26, 2015, http://www.koreaherald.com/view.php?ud=20150226000661; “Kita Misairu, Tan-Chu Kyoridan mo Kaku Tosai Funo: Beikokumusho ga Koshiki Kenkai” [North
Korean Missiles, Nuclear Weapons Cannot Yet be Mounted on Short- or Medium-range Ballistic Missiles: US State Dept.
Releases Official Position], Sankei Shimbun, May 23, 2015, http://www.sankei.com/world/news/150523/wor1505230020-n1.

16html.
18. David Francis, “North Korea’s Nuclear Program Advancing, U.S. Military Leader Says,” Foreign Policy, October 24, 2014,
http://thecable.foreignpolicy.com/posts/2014/10/24/north_korea_s_nuclear_program_advancing_us_ military_leader_ says.
19. Japan Ministry of Defense, Defense of Japan 2015 [Annual White Paper], 2015, p. 19.
20. Japan Ministry of Defense, Defense of Japan 2016 [Annual White Paper], 2016, p. 23.
21. On the North Korea’s ballistic missile capability and development, see, for instance, John Schilling and Henry Kan, “The
Future of North Korean Nuclear Delivery Systems,” US-Korea Institute at SAIS, 2015.
22. Ibid., pp. 11-12.
23. “NORAD Commander: North Korean KN-08 Missile Operational,” Stars and Stripes, April 7, 2015, http://www.stripes.
com/news/norad-commander-north-korean-kn-08-missile-operational-1.338909.
24. “Kita Chosen: SLBM, Kansei ni 4–5 Nen; Suichu Hassha de Kankokugun” [North Korea to complete SLBM within four tofive years; Underwater launch threatens South Korean military], Mainichi Shimbun, May 12, 2015, http://mainichi.jp/
shimen/news/20150512ddm002030091000c.html?inb=ra.
25. In addition to those mentioned in this article, North Korea’s aims may also include, inter alia, to force political and diplomatic concessions; to “efficiently” utilize resources to bolster deterrent capabilities, and thereby to reallocate such resources
to other priorities; and to transfer nuclear- and missile-related items and technology to a third country in order to acquire
hard currency. Also, the testing of nuclear weapons, long-range ballistic missiles and so on may well aim for internal political purposes, such as demonstrating its strength in order to consolidate the Kim dynasty’s power base, besides having themilitary objectives of developing weapons and improving their performance for strengthening its deterrence.
26. Regarding North Korea’s nuclear strategies, see, for instance, Shane Smith, “North Korea’s Evolving Nuclear Strategy,” North
Korea’s Nuclear Future Series, US-Korea Institute at SAIS, August 2015; Vipin Narang, “Nuclear Strategies of Emerging
Nuclear Powers: North Korea and Iran,”Washington Quarterly, Vol. 38, No. 1 (Spring 2015), p. 80.
27. “Law on Consolidating Position of Nuclear Weapons State Adopted.”
28. For an argument that extended deterrence is undermined by the “stability-instability paradox,” see Robert Jervis, “Deterrence,Rogue States, and the U.S. Policy,” T. V. Paul, Patrick M. Morgan and James J. Wirtz, eds., Complex Deterrence: Strategy in
the Global Age (Chicago: The University of Chicago Press, 2009), p. 138.
29. Hideya Kurata, “Beichu Kankei to Chosen Hanto” [US-China relations and the Korean Peninsula], US-China Relations
Report, Vol. 5, September 15, 2015, http://www2.jiia.or.jp/RESR/column_page.php?id=246. (in Japanese)
30. Robert Carlin and Robert Jervis, “Nuclear North Korea: How Will It Behave?” North Korea’s Nuclear Futures Series, USKorea Institute at SAIS, October 2015, pp. 7-8. Carlin and his colleague argue that there is both a possibility that North
Korea will become more aggressive as its nuclear capability increases, and a possibility that it will become more restrained.
Ibid., pp. 10-13.
31. Ken Watman and Dean A. Wilkening, U.S. Regional Deterrence Strategy (Santa Monica: RAND, 1995).
32. See, for instance, Robert Jervis, “Deterrence Theory Revisited,” World Politics, Vol. 31, No. 2 (January 1979), pp. 312-314.
33. For an argument that such a communication problem makes deterrence more complex, see, inter alia, Michael Tkacik,“Regional Nuclear Powers and U.S. Policy: A Study in Asymmetries,” Owen C.W. Price and Jenifer Mackby, eds., Debating
21st Century Nuclear Issues (Washington, D.C.: Center for Strategic and International Studies, 2007), pp. 14-23; T.V. Paul,“Complex Deterrence: An Introduction,” T.V. Paul, Patrick M. Morgan and James J. Wirtz, eds., Complex Deterrence: Strategy
in the Global Age (Chicago: University of Chicago Press, 2009), p. 9.
34. On a possibility of deterrence failure caused by recognition bias, see, inter alia, Jervis, “Deterrence Theory Revisited,” pp.
305-310.
35. In October 2012, South Korea agreed with the United States to extend the range limitation of ballistic missiles from 300 km
to 800 km (and throw weight up to 500 kg). Prior to this, in July, Seoul announced the deployment of its new land attack
cruise missile Hyunmoo 3C, with a range of 1,500 km.
36. “Kankoku ga ‘Kokubo Kaikaku Kihon Keikaku’ Go-nen Inai ni Sakusen Taikei Kaihen” [South Korea to complete strategy
reorganization of ’Defense Reform Basic Plan’ within five years] Rengou Nyuusu [Yonhap News], March 6, 2014, http://
japanese.yonhapnews.co.kr/headline/ 2014/03/06/0200000000 AJP201403060001000882.HTML.
37. “Kita Chosen Shisetsu Nado Hakai Ninmu Suiko Tokushu Butai Hensei e: Kankoku Rikugun”[Special unit being formed toattack North Korean nuclear facilities: South Korean Army] Rengou Nyuusu [Yonhap News] September, 23, 2015, http://
japanese.yonhapnews.co.kr/Politics2/2015/09/23/0900000000AJP20150923002700882.HTML.
38. “Joint Statement of the 2014 United States-Republic of Korea Foreign and Defense Ministers’ Meeting,” October 24, 2014,17

http://www.state.gov/r/pa/prs/ps/2014/10/233340.htm.
39. “Kita Chosen Hogeki Chohatsu Kim Yoken ‘Shushu Shiyo’ So Sanbobu Ha ‘Gunji Kodo’: Kita Chosen No Ryoumen
Senjutsu,”[Kim Yang-gon: ‘Let’s settle this’; General Staff Department ‘Military action’—North Korea’s double-sided strategy] Chuo Nippo [JoongAng Ilbo] August 21, 2015, http://japanese.joins.com/article/706/204706.html/.
40. “Joint Press Release from the Inter-Korean High-Level Meeting,” August 25, 2015, http://english1.president.go.kr/activity/
briefing.php?srh%5Bboard_no%5D=21&srh%5Bview_mode%5D=detail&srh%5Bseq%5D=11845&srh%5Bdetail_no%5D=365.
41. Kim Jong-un claimed that it was not negotiating skill that brought about the “epoch-making” agreement that averted a
military conflict with the South on August 25, but North Korea’s possession of nuclear weapons. “Kim Jong Un Guides
Enlarged Meeting of WPK Central Military Commission,” KCNA, August 28, 2015, http://www.kcna.co.jp/item/2015/201508/
news28/20150828-01ee.html.
42. As an argument that leaders under attack by precision guided weapons may panic and opt to use their nuclear capability
rather than lose it, and that the superiority of conventional forces over weak nuclear weapons possessors would lowers thenuclear threshold, see Michel Fortmann and Stefanie von Hlatky, “The Revolution in Military Affairs: Impact of Emerging
Technologies on Deterrence,” Paul, Morgan and Wirtz, eds., Complex Deterrence, pp. 316-317.
43. “Cabinet Decision on Development of Seamless Security Legislation to Ensure Japan’s Survival and Protect its People,”
Prime Minister of Japan and his Cabinet, July 1, 2014, http://japan.kantei.go.jp/96_abe/decisions/2014/__icsFiles/afieldfile/
2014/07/03/anpohosei_eng.pdf. The three conditions are: “when an armed attack against Japan occurs or when an armed
attack against a foreign country that is in a close relationship with Japan occurs and as a result threatens Japan’s survival andposes a clear danger to fundamentally overturn people’s right to life, liberty and pursuit of happiness”; “when there is noother appropriate means available to repel the attack and ensure Japan’s survival and protects its people”; and “use of force
should be limited to the minimum extent necessary.”
44. There is also an argument that the US restraint on using nuclear weapons against regional nuclear armed states would contribute to its national interest. See Adam Mount, “The Strategic Logic of Nuclear Restraint,” Survival, Vol. 57, No. 4 (AugustSeptember 2015), pp. 53-76.
45. “Provokers Will Meet Miserable End: Rodong Sinmun,” KCNA, March 31, 2013, http://www.kcna.co.jp/item/2013/201303/
news31/20130331-13ee.html.
46. “Rodong Sinmun Denounces Japan’s Hostile Moves against DPRK,” KCNA, April 10, 2013, http://www.kcna.co.jp/
item/2013/201304/news10/20130410-14ee.html.
47. “Why Does U.S. Attaches So Great Importance to Okinawa,” KCNA, July 3, 2013, http://www.kcna.co.jp/item/2013/201307/
news03/20130703-13ee.html.
48. For an argument that the issue of intra-war deterrence is the most important deterrence challenge facing the United States,
see Keir A. Lieber and Daryl G. Press, “Coercive Nuclear Campaigns in the 21st Century: Understanding Adversary
Incentives and Options for Nuclear Escalation,” PASCC Report, March 2013.
49. In the three conditions for the exercise of the right of self-defense, the condition of “[U]se of force should be limited to theminimum extent necessary” has not been changed. According to interpretation of the constitution, though there may bechanges to the international situation and levels of military technology, “the possession of weapons purely to inflict catastrophic destruction on an opponent’s territory from a performance perspective would immediately exceed the boundariesof the minimum necessary level, and could not be permitted under any circumstances, so that, for example, the possession
by the Self-Defense Forces of ICBM, long-range strategic bombers or attack type carriers cannot be permitted.” (Responseby Souichirou Ito, Director General of the Defense Agency to the House of Representatives Budget Committee, March 20,
1982;

http://kokkai.ndl.go.jp/cgi-bin/KENSAKU/swk_dispdoc.cgi?SESSION=36673&SAVED_RID=3&PAGE=0&POS=

0&TOTAL=0&SRV_ID=5&DOC_ID=10649&DPAGE=1&DTOTAL=1&DPOS=1&SORT_DIR=1&SORT_TYPE=
0&MODE=1&DMY=39618), so the possession of a punitive deterrence would not be constitutionally acceptable.
50. Lawrence Freedman, Deterrence (Cambridge: Polity Press, 2004), p. 39.
51. The orders given in March 2009, March 2012, December 2012, and April 2013 were all publicly announced, but not in April
2014. The order given in January 2016 was initially classified, but the order was reissued and announced in February.
52. Ken Jimbo, “Abe Seikenka de no Shimuresu na Anzen Hosho Taisei no Mosaku—Boei Keikaku no Taiko / Nichibei Boei
Kyoryoku no Gaidorain / Anzen Hosho Hosei” [In Search of a Seamless Security Posture under the Abe Administration:
National Defense Program Guidelines, US-Japan Defense Cooperation Guidelines, and Security Legislation], Mondai to
Kenkyu [Issues and Studies], Vol. 44, No. 2 (April, May, June 2015), p. 53. (in Japanese)1853. Hideaki Kaneda, Kazumasa Kobayashi, Hiroshi Tajima, Hirofumi Tosaki “Nihon no Misairu Boei—Henbo suru Senryaku
Kankyoka no Gaiko / Anzen Hosho Seisaku” [Japan’s Missile Defense—Diplomacy and Security Policy in a Changing
Strategic Environment], Nihon Kokusai Mondai Kenkyujo [Japan Institute of International Affairs], 2006. (in Japanese)
54. See Yuichiro Hitoshi, “Senshu Boei Rongi no Gendankai—Kenpo Dai Kyujou, Nichibei Domei, soshite Kokusai Anzen
Hosho no Aida ni Yureru Gensoku” [Current State of Debate on Non-aggressive Defense—Principles That Sway Between
Article Nine of the Constitution, the Japan-US Alliance and International Security], Rifarensu [Reference] No. 664 (May2006), pp. 31-34.
55. Sugio Takahashi, “Senshu Boeika no Tekichi Kogeki Noryoku wo Megutte: Dando Misairu Kyoi e no Hitotsu no Taio”[Coping with a Ballistic Missile Threat: Strike Capability under an Exclusively Defense-Oriented Policy], Boei Kenkyujo
Kiyo [NIDS Security Reports], National Institute of Defense and Security Journal, Vol. 8, No. 1 (October 2005), p. 118. (inJapanese)
56. However, it has been argued that the B61-12, currently being developed as a consolidation and replacement of the existing
B61 series of gravity nuclear bombs, might have earth-penetrating capability. See Hans Kristensen, “Video Shows EarthPenetrating Capability of B61-12 Nuclear Bomb,” Federation of American Scientists, January 14, 2016, https://fas.org/blogs/
security/2016/01/b61-12_earth-penetration/.
57. See Takashi Hayashi, “Nikkan Gunji Joho Hokatsu Hogo Kyotei (Nikkan GSOMIA) Teiketsu Enki no Yoin Bunseki —Shomei 1-Jikan Mae no Dotanba de Seisaku Henko Sareta Haikei ni Atta Mono” [Analysis of Factors for Adjournment of
the Japan-South Korea General Security of Military Information Agreement (GSOMIA): Factors for the Policy Change
Made at the Last Moment, just an Hour Prior to Reaching the Agreement], Kaikanko Senryaku Kenkyu [JMSDF Staff
College Review] , Vol. 4, No. 2 (December 2014), pp. 76-98. (in Japanese)
58. “S. Korea, U.S., Japan Sign Pact on Sharing N.K. Intel,” Yonhap News Agency, December 29, 2014, http://english.yonhapnews.co.kr/national/2014/12/29/59/0301000000 AEN20141229004300315F.html.
59. In addition to the issue of a US deployment of the Theater High Altitude Area Defense (THAAD) system on South Koreansoil, Seoul prioritized its deepening relationship with China, and was not positively inclined towards BMD cooperation
with Japan and the United States. However, after the North Korea nuclear tests, the South has changed its stance on the
THAAD deployment.

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