Nuclear Evaluation of the Washington Declaration and Implications for Japan

The Washington Declaration, a military declaration of intent between the United States and the Republic of Korea (ROK, South Korea), has been a sensitive topic for China. Recently, Chinese officials have increased the airing of their concerns over the implications of this alliance. Mao Ning, deputy press secretary of the Chinese Foreign Ministry, expressed “firm opposition” to the Washington Declaration, saying that it “intensifies tensions on the Korean Peninsula and destroys peace and stability in the region. She accused the US of "creating tensions under the guise of the Korean Peninsula issue” in order to “achieve its own geopolitical self-interest”. The Washington Declaration aims solely at strengthening deterrence against the Democratic People’s Republic of Korea (DPRK, North Korea) but due to the geographical proximity of the Korean Peninsula and China, it is argued that such deterrence could lead to an expanded armed conflict that spills over onto Chinese soil. In addition, Beijing has expressed concerns over the US using the alliance as a pretense for surveillance of Chinese military assets and has persistently opposed the deployment of Terminal High Altitude Area Defense (THAAD) in the ROK due to the potential of early warning radar coverage reaching deep into China.

Although the Japanese government has not made any official comments, Japanese experts on nuclear issues have generally been supportive of the alliance. Masaru Murano of the Hudson Institute, for example, praised the Washington Declaration as (1) dispelling growing concerns within the ROK about US extended deterrence credibility, (2) reaffirming US defense commitments to the ROK involving the entire range of US military capability, including nuclear weapons, and (3) reaffirming the ROK’s commitment to abide by the Nuclear Nonproliferation Treaty. Murano also commented that the Washington Declaration could be turned into an opportunity to strengthen extended deterrence in the region if the countries concerned can take this opportunity to work together in an appropriate manner. The significance of these comments from Japanese experts stems from the fact that both the ROK and Japan share both the same regional threats as well as the same reliance on US military support for extended deterrence. However, four months after the Washington Declaration, at the trilateral summit at Camp David, the Washington Declaration (plus Japan) was not included in the trilateral framework of extended deterrence.

This paper will discuss the evaluation of the US-ROK Washington Declaration and its implications for Japan’s nuclear deterrence policy.

Evaluation of the Washington Declaration

The Washington Declaration is the result of the US-ROK alliance’s continuous updating of the alliance coordination mechanism and continues to serve as a symbol of credibility for Korean peninsula extended deterrence.

The beginning of the US-ROK extended deterrence consultation was the Extended Deterrence Policy Consultation (EDPC) in 2010, which then evolved to the ROK-US Tailored Deterrence Strategy (TDS) in 2013, the Deterrence Strategy Committee (DSC) in 2015, and the Extend Deterrence Strategy and Consultative Group (EDSCG) in 2016. Except for the five years of the Moon Jae-in administration, both countries have worked closely and continuously to improve the credibility of their deterrence posture.

The four programs, along with the newly established Nuclear Consultative Group (NCG), would thus develop the scheme for discussing extended deterrence that the alliance has developed in stages and greatly improved its visibility.

The Washington Declaration is a nuclear sharing scheme, a policy designed to provide reassurance from states that possess nuclear weapons to those that do not, and has three objectives: extended deterrence, alliance management, and maintenance of nuclear nonproliferation policies.

The NCG will only consult on issues of contingency nuclear planning and nuclear deterrence approaches with the goal of enhancing extended deterrence and will not make policy decisions on the use of nuclear weapons. If the NCG were to someday combine its current role with planning for the use of tactical nuclear weapons, it would expand closer to the nature of NATO's Nuclear Planning Group (NPG), a development which would further enhance extended deterrence credibility.　

President Yoon’s enthusiasm for ensuring extended deterrence credibility is certainly commendable. The Yoon administration reactivated the EDSCG in 2022 after a five-year hiatus during the Moon Jae-in administration, and within a very short period of time after taking office, President Yoon established the Washington Declaration. His enthusiasm for nuclear deterrence is not limited to the Korean Peninsula—he is reportedly open to the idea of Japan and the ROK cooperating to respond to the DPRK nuclear threat.

One example of President Yoon’s authentic commitment to deterrence is his normalization of the ROK-Japan General Security of Military Information Agreement (GSOMIA), formerly used merely as a diplomatic bargaining tool by President Moon, amid North Korea’s repeated missile launches. At the ROK-Japan summit meeting in March 2023, the two leaders agreed to further advance the deterrence and response capabilities of the Japan-US alliance and the ROK-US alliance. In May, President Yoon additionally said that he did not rule out Japan joining the Washington Declaration’s extended deterrence framework.

A result of President Yoon’s leadership is that the Washington Declaration succeeded in linking ROK conventional support to US nuclear operations, making the extended deterrence regime more feasible and realistic.

The US and ROK have the Combined Force Command (CFC) which enables close conventional operations from peacetime to war time. The extended deterrence is combined organically with this defense posture. Although the content of conventional support isn’t disclosed, its incorporation into the CFC’s operational plans will greatly improve nuclear deterrence on the Korean Peninsula. If ROK conventional support includes support for regular port calls by USN SSBNs equipped with low-yield nuclear ballistic missiles, which the US government provides as a visible extended deterrent option, a primary area of operation will be the sea. Therefore, the requirement of coordinating and aligning the US-Japan alliance on the management of the undersea domain may arise in future.

The Washington Declaration has many similarities to the expansion of NATO's nuclear sharing program, which is expected to enhance the credibility of extended deterrence on the Korean Peninsula in the same way that it has curbed the budding concerns among NATO member nations regarding decoupling the US from Europe.

There are similarities between the current Korean Peninsula and the European strategic environment of the 1970s. The current NATO nuclear sharing has its origins in the Nuclear Stockpile in the 1950s, a means of the US so-called massive retaliation strategy (deterrence by punishment) to compensate for NATO's inferior conventional forces with the superiority of US nuclear forces.

Based on that strategy, the administration of US President Dwight D. Eisenhower  initiated the nuclearization of NATO. The contents of this plan included stockpiling tactical nuclear weapons in NATO member nations and the deployment of various means of delivery, such as cruise missiles and dual capable aircraft (DCA). Eventually, the Soviet Union's successful ICBM test in August 1957 and launch of Sputnik in October 1957 caused NATO to become increasingly concerned about the extended deterrence credibility of the US and possibility of the US exiting NATO. The Eisenhower administration assuaged allied concerns with a nuclear stockpile system, forward deployment of IRBMs, and having nuclear forces operate under the command of Supreme Allied Command Europe (SACEUR). After 1965, the US administration shifted toward strengthening extended deterrence credibility while maintaining the NPT system, creating the Nuclear Planning Group (NPG) to discuss nuclear policy and related issues. This was a shift from hardware to a software based nuclear sharing regime.

The DPRK’s ICBM development has parallels to the Sputnik Shock with and its effect of catalyzing concerns about fragmenting alliances.

The DPRK has shown a willingness to use nuclear weapons preemptively in the case that an armed conflict inside the Korean Peninsula escalates into an intervention with US forces operating in the ROK and Japan.

On September 8, 2022, the DPRK’s Supreme People’s Assembly promulgated the Law on the State Policy on Nuclear Forces (Nuclear Force Policy Law) that prescribes principles and conditions of nuclear force employment. It clearly stated that Pyongyang could use nuclear weapons at its arbitrary discretion, such as when a military attack on North Korea is “perceived” to be imminent. The DPRK’s continuous nuclear and missile development, combined with this nuclear policy, has caused heated political debates in the ROK.

The DPRK is estimated to possess 40 nuclear warheads. The power achieved in the sixth test (September 2016) is estimated to be 160 kilotons, which is about 11 times more powerful than the Hiroshima-type atomic bomb (15 kilotons). Given this technological maturity, it is believed that the DPRK has already achieved the miniaturization and warheading of nuclear warheads.

The DPRK has launched various types of missiles more than 170 times since the Kim Jong-un regime came to power in 2016, and it has repeatedly launched ICBM-class missiles and SLBMs. ICBM-class missiles have been launched 14 times in the six years since July 2017, with seven of those launches concentrated in the two years since President Yoon took office. It is no surprise, then, that a series of ICBM launches has raised concerns among the South Korean government and public about a breakdown of the alliance, similar to what threatened to happen after the Sputnik Shock of 1957.

However, the Washington Declaration did not choose the same “visible” hardware nuclear sharing as NATO—forward stockpiling of nuclear bombs, deployment of Dual Capable Aircrafts (DCAs), and providing visible reassurance—opting instead for “semi-visible” means of regular port calls by SSBNs. The port call to Korean ports may fill a missing step in the escalation ladder, but it does not possess much military significance and was added more for political reasons.        

Implications for Japan

The Washington Declaration reveals differences between the approaches of Japan and the ROK regarding the means to ensure extended deterrence credibility.　

The US-Japan alliance has continued the Extended Deterrence Dialogue (EDD) since 2010, and there is no policy gap in the alliance regarding extended deterrence. Since Japan has been actively strengthening its ballistic missile defense capabilities to complement extended deterrence, Japan’s nuclear deterrence policy can be described as “deterrence by denial” combined with the US extended deterrence.

On the other hand, in the Washington Declaration, the ROK government appears to emphasize “deterrence by punishment” with regard to deterring the DPRK. For example, on the promulgation of Nuclear Force Policy Law, the US and ROK jointly stated that any nuclear attack by Pyongyang would be met with an overwhelming and decisive response.

The difference in approach can be attributed to the histories and strategic environments of the two countries. The Korean War is in armistice, and the ROK has been constantly challenged militarily by the DPRK since then for 70 years, such as in the Battle of Daecheong in 2009, the sinking of the ROK Navy’s corvette Cheonan and the shelling of Yeonpyong Island in 2010, among other incidents.

The DPRK is a belligerent and an imminent threat to the ROK. Moreover, the threat of the North is growing every day. Therefore, it is quite natural that the DPRK's nuclear and ballistic missile development is perceived as an even more imminent threat to ROK than it is to Japan. The shortage of ROK’s warning time to counter a DPRK surprise attack inevitably demands more proactive extended deterrence measures than what Japan needs.

In the event of an accidental military conflict on the Korean Peninsula, and if it escalates to a war, the US-ROK alliance would launch a conventional attack inside North Korea with unmatched military power. As a counterattack, the DPRK might carry out nuclear demonstrations in a limited manner to force the alliance to make peace on the DPRK’s terms. If the US extended deterrence posture becomes more credible, the US-Korea alliance could more effectively dissuade North Korea from using nuclear arms.

Japan, on the other hand, is separated from the Korean Peninsula by sea, and the memory of Hiroshima and Nagasaki has cultivated a stronger sentiment to avoid any nuclear issues. Nevertheless, when Russia used nuclear weapons for intimidation in the Ukraine war, there grew a bigger concern regarding the extended deterrence credibility in the Japanese strategic community. Much of the discussion was about the pros and cons of introducing NATO’s nuclear sharing program to Japan, but it did not lead to a change in nuclear policy. Prime Minister Kishida said that nuclear sharing should be discussed but added that neither bringing nuclear weapons into Japanese territory during peacetime, nor the operation of US nuclear weapons by the Self-Defense Forces in an emergency, was acceptable.

However, there are still possibilities for Japan to cooperate with the extended deterrence regime of the ROK-US alliance.

First, the Japanese government could provide conventional support to the US Navy SSBNs' regular port calls to the ROK. According to Murano of the Hudson Institute, Japan could provide similar level support as NATO's SNOWCAT (Support for Nuclear Operations with Conventional Air Tactics) by providing asset protection to SSBNs.

During a SSBN transit in waters surrounding Japan to the Korean Peninsula, the US Seventh Fleet would provide both direct and indirect protection. While SSBNs navigate Japanese waters, the Self Defense Force can provide surveillance support and intelligence support. It would also be possible for Japanese and South Korean air forces to cooperatively escort B-52 bombers on demonstration flights from Guam to the Korean Peninsula.

Secondly, Japan’s new defense capabilities, including standoff capabilities, are likely to be a part of extended deterrence. If the Japanese government wants to operate the capabilities more efficiently and effectively, the kill chain must be operated jointly by Japan and the United States. The close coordination with the ROK is required when attacking targets inside North Korea. In addition, if Japan's new defense capabilities can be organically linked to the US extended deterrence capability, the Japan-US alliance can expand its options in every phase of defensive operations, an effect that will surely spread to the Korean Peninsula as well.

Another possibility is the necessity to strengthen comprehensive deterrence against China through Japan, the US, and South Korea trilateral cooperation. According to the US Department of Defense, China is rapidly building up its nuclear capability, and it will likely field a stockpile of about 1,500 warheads by 2035. As a result, China will have a capability of mutually assured destruction against the United States. In addition, given China's faster-than-expected buildup of conventional forces, a strategic environment similar to that of Europe in the 1970s will emerge in the Indo-Pacific in the 2030s. As a result, an emerging strategic environment will inevitably increase fragmentation concerns for US allies.

Although the nuclear consultation in the Washington Declaration focuses primarily on the DPRK as a threat, extended deterrence against China must also be the subject of consideration. And in that case, concerted action with Japan, which regards China as their greatest strategic challenge, is also required. In addition, countries that depend on US extended deterrence will need to strengthen cooperation and continue efforts to integrate their conventional forces with US strategic nuclear weapons.

There are no certainties

The Washington Declaration is a major achievement and result of President Yoon Suk Yeol's enthusiasm. The declaration also has symbolic significance in breaking with the Moon Jae-in administration’s appeasement policy as well as strengthening the defense posture against the DPRK.

The DPRK’s nuclear and ballistic missile development continues without abatement. On the completion of ICBM development, it will have a nuclear escalation ladder that includes a strategic nuclear weapon aimed at the United States. At that time, the ROK’s sole “deterrence by retaliation” will not be enough to stop the DPRK’s first strike. As the same situation also applies to Japan, both Japan and ROK are required to shift the basic principle of deterrence from retaliation to damage limitation, while working tirelessly to enhance extended deterrence credibility and maintaining the preparation and potential to use nuclear weapons if the need arises.

Lastly, we must remember that when it comes to dealing with autocrats, there are no certainties.