Iku Tsujihiro is an MA candidate in the Security Studies Program (SSP) at the School of Foreign Service, Georgetown University. She focuses on the U.S.-Japan economic and energy security alliance, U.S. military operations in the Indo-Pacific, and nuclear deterrence in Northeast Asia. Currently, she is a research intern for Hudson Institute’s Japan Chair Policy Center. She is selected to be on the Center for Strategic and International Studies’ Nuclear Scholars Initiative (NSI) Fellowship. Divergent Options’ content does not contain information of an official nature nor does the content represent the official position of any government, any organization, or any group.

National Security Situation:  The Democratic People’s Republic of Korea’s (DPRK) has grown increasingly hostile towards Japan via its ballistic missile tests.

Date Originally Written:  December 19th, 2023.

Date Originally Published:  February 12, 2024.

Author and / or Article Point of View:  The author believes that while U.S. nuclear umbrella guarantees towards Japan remain untested; however, the DPRK continued proliferation and refinement of ballistic missile and nuclear missile technology indicate that the U.S. nuclear policy in Northeast Asia may be outdated.

Background:  The DPRK has been increasingly provocative with its ballistic missile tests toward Japan’s Exclusive Economic Zone under Kim Jong-Un’s regime compared to Kim Jong Il. In 2022 only, the DPRK launched its ballistic missiles towards Japan more than 60 times[1]. Meanwhile, under Kim Jong-Il’s leadership, DPRK tested its ballistic missile capabilities only 16 times and nuclear weapons twice[2]. 

Although no DPRK missiles have struck Japanese territory yet, the Japanese public is increasingly aware and concerned over the threat.  This concern is best reflected in increased frequency in government and news alerts regarding the potential danger of DPRK missiles falling on Japanese territory. The most recent incident occurred on December 18, 2023, in which the DPRK launched an Intercontinental Ballistic Missile (ICBM) in a “lofted orbit” trajectory. The fastest speed of the ICBM was estimated to be up to 6000km/h. Deterring the DPRK’s expanding missile capabilities is Japan’s one of top priorities as it is stated in the 2023 version of Japan’s Annual White Paper[3].

Significance:  The DPRK’s missile tests toward Japan are steadily eroding the credibility of the current U.S. extended deterrence policy — U.S. nuclear umbrella over Japan — which assure U.S. retaliation against any country that attacks Japan with a nuclear weapon. The Japanese public is increasingly skeptical of the credibility of U.S. nuclear umbrella, both in terms of willingness and capability[4]. The U.S. requires new and appropriate alternatives to its current U.S. extended deterrence approach and nuclear umbrella to assure the credibility of the extended deterrence in Japan. This credibility relies heavily on public perception and trusts. 

Option 1:  The United States engages in North Atlantic Treaty Organization-style nuclear sharing with Japan.

With advancements in the DPRK’s missile program and the escalating pattern of DPRK provocation with its recent testing, the lack of action and deafening silence by the United States are growing concerns in Japan. Some senior Japanese lawmakers have been considering alternatives, such as nuclear sharing. Nuclear sharing is when the United States deploys and stations B-61 (tactical nuclear weapons) on its allies’ land while maintaining full control and custody of the weapons[5]. This perspective originated from former Japanese Prime Minister Shinzo Abe, who stated nuclear sharing is necessary for nuclear deterrence against nuclear countries like the DPRK and China after witnessing the Russian invasion of Ukraine[6]. 

Risk:  As the Republic of Korea (ROK) has been more public with its growing doubt of U.S. extended deterrence, the ROK would demand the same U.S. nuclear sharing that Japan receives under this option[7].  This demand would encourage further proliferation to non-nuclear weapon states and potentially escalate the security tension in the Indo-Pacific. The adversaries may increase their nuclear build-up in return, escalating arms race. 

Gain:  Nuclear sharing will reassure the Japanese public and politicians who are skeptical about the current U.S. extended deterrence method. Since the credibility of nuclear deterrence heavily relies on public perceptions and trusts, this option allows to bridge the gap between the Japanese and U.S. extended deterrence method. 

Option 2:  Japan and the United States establish the Washington Declaration.

In this option, the United States issues something like the U.S.-ROK Washington Declaration with Japan to display the continued trust in the alliance and defense treaties. The declaration reassures the ROK through dispelling the skepticisms of the credibility of U.S. extended deterrence and reaffirms U.S.-ROK defense commitments. Within the ROK context, this declaration also institutes a Nuclear Consultative Group, which enables the ROK to have a more powerful voice in retaliation decisions[8].

Risk:  The declaration in this option could cause negative reactions from adversaries including China, as the U.S.-ROK Washington Declaration triggered a response from the Chinese Foreign Ministry[9]. Though the declaration is less provocative than U.S. nuclear sharing to Japan, it will likely raise the tension between the U.S. allies and adversaries. Additionally, the declaration may not satisfy the crowd rooting for nuclear sharing.

Gain:  Although there are no official conversations on this option in Japan currently, the declaration can reassure Japan with its extended deterrence commitments. Moreover, the United States establishing the same declaration between the ROK and Japan could open the door for further security cooperation between the ROK and Japan, recognizing that they have a shared adversary to counter[10].

Other Comments:  In the end, public perception will play a significant role in determining the success or failure of the U.S. nuclear umbrella in the Indo-Pacific, and if the United States is not careful – its promises may fall on deaf ears. 

Recommendation:  None.

Endnotes:

[1] Fukuda, K. (2023, April 19). North Korea, a dangerous entity whose only option is nuclear weapons. Toyo Keizai. https://toyokeizai.net/articles/-/667431?display=b

[2] (2023, February). Development of Nuclear and Ballistic Missiles by North Korea. Ministry of Defense of Japan. https://www.mod.go.jp/j/surround/pdf/dprk_bm_2023.pdf 

[3] Defense of Japan 2023. Ministry of Defense. 

[4] Yoshida, S. (2019, October 20). Mixed messages on nuclear deterrence. The Japan Times. https://www.japantimes.co.jp/opinion/2019/10/20/commentary/japan-commentary/mixed-messages-nuclear-deterrence/. 

[5] (2022, February). NATO’s Nuclear Sharing Arrangements. North Atlantic Treaty Organization. 

[6] Tobita, R. (2022, March 12). Senior Japanese Lawmakers Eye “Nuclear Sharing” Option with U.S.. Nikkei Asia. https://asia.nikkei.com/Politics/Senior-Japanese-lawmakers-eye-nuclear-sharing-option-with-U.S. 

[7] Bae, M. (2019, December 19). Can South Korea and Japan Share Nuclear Weapons with the U.S.?. JoongAng Ilbo. https://japanese.joins.com/JArticle/260711?sectcode=120&servcode=100

[8] (2023, April 26). Washington Declaration. The White House. https://www.whitehouse.gov/briefing-room/statements-releases/2023/04/26/washington-declaration-2/. 

[9] Takei, T. (2024, January 19). Evaluation of the Washington Declaration and Implications for Japan. Perry World House. https://global.upenn.edu/perryworldhouse/news/evaluation-washington-declaration-and-implications-japan.

[10]  Ibid.