In February 2018, the Department of Defense released the Trump administration’s Nuclear Posture Review (NPR). This document outlines U.S. policy regarding the role of nuclear weapons in U.S. national security strategy and the capabilities needed to meet those requirements, among other topics. The NPR also serves as a valuable signaling tool for U.S. allies, partners, and adversaries around the globe. Given advancements in North Korea’s nuclear and missile programs, the NPR indicates that two central U.S. goals are deterring North Korean aggression and assuring South Korea and Japan of the strength of the U.S. nuclear umbrella. To counter North Korean aggression, the NPR offers a tailored deterrence strategy. This includes 1) calling for “a complete, verifiable, and irreversible nuclear freeze;” 2) clearly communicating to North Korea that any use of a nuclear weapon against the U.S. or it allies “will result in the end of [the Kim] regime;” 3) the deployment of early warning and missile defense systems “to degrade strikes left of launch”; and 4) retaining a variety of nuclear and conventional capabilities in the region to hold North Korean nuclear targets at risk.1 The choice of words regarding the third element is particularly revealing. “Left of launch” is generally understood to indicate a preventive or preemptive strike. Additionally, use of the word “degrade” acknowledges such an endeavor would not likely be one-hundred percent effective at eliminating North Korea’s nuclear capability. North Korea’s response to the 2018 NPR was immediate and overwhelmingly negative. According to media reports, North Korean officials condemned the document as tantamount to “a declaration of war against the whole world.”2 As fears grew that this war of words would lead to a kinetic conflict, a window of opportunity to de-escalate the situation presented itself in conjunction with the Winter Olympics.3 In the wake of this détente, it is worth examining whether the 2018 NPR is achieving one of its intended purposes—assuring allies in East Asia. South Korea Nowhere is the North Korean nuclear and missile threat more palpable than in South Korea. According to the Congressional Research Service, even without using a nuclear weapon, a North Korean attack against Seoul could result in hundreds of thousands of casualties in the first few hours.4 If the conflict involved nuclear weapons, those numbers could climb to the tens of millions including not only South Korean deaths but also American and Japanese fatalities. Since 1954, the United States and South Korea have maintained a mutual security agreement that has focused on defending the South from attacks by North Korea. The treaty has also served as a non-proliferation tool by bringing South Korea under the U.S. nuclear umbrella thus obviating the need for South Korea to develop its own nuclear weapons capacity. As North Korea’s nuclear and missile programs have advanced, the South Korean public has become more embracing of a more assertive nuclear posture. Polls indicate that 60% of the public supports a South Korean nuclear weapons program and 68% of the public supports redeployment of U.S. tactical nuclear weapons (TNWs).5 This sentiment has been echoed by leaders of the South Korean opposition party as well as in the United States.6 President Moon has remained firmly against such a move. While the decision to redeploy TNWs in South Korean is outside the purview of the 2018 NPR, the document seeks to demonstrate the resolve of U.S. extended deterrence and thereby counteract incentives for South Korea to pursue its own nuclear capabilities. This is partially achieved by calling for the development of submarine launched cruise missile (SLCM) as well as low-yield sea launched ballistic missile to provide a more flexible deterrent. Although the NPR does not explicitly link these capabilities to the North Korean threat, it implies they would play a key role assuring allies in Asia: In the 2010 NPR, the United States announced the retirement of its previous nuclear-armed SLCM, which for decades had contributed to deterrence and the assurance of allies, particularly in Asia. Given the increasing need for flexible and low-yield options to strengthen deterrence and assurance, we will immediately begin efforts to restore this capability by initiating a capabilities study leading to an Analysis of Alternatives (AoA) for the rapid development of a modern SLCM.7 The South Korean response to the 2018 NPR has been positive. Speaking on the condition of anonymity one foreign ministry official was quoted saying, “Our government evaluates that the review has reaffirmed (Washington’s) pledge to provide extended deterrence to South Korea and other allies. South Korea and the U.S. will continue to cooperate in enhancing the promised extended deterrence.”8 It is possible the assurances offered by the 2018 NPR helped create the necessary conditions for the April 27 summit between Kim and Moon. In this regard the NPR may have served as a confidence building measure for the ROK government and Korean public by demonstrating the credibility of U.S. extended deterrence. By all accounts, the initial summit meeting between the two leaders appears to have gone well and laid the foundation for a subsequent meeting between Kim and President Trump. Kim Jong-Un has indicated a willingness to denuclearize for an end to the Korean War and promises by the U.S. not to seek regime change in North Korea.9 However, it is important to note that the term “denuclearize” is undefined and holds different meanings for both North Korea and the United States that could prove an impediment to future negotiations.10 Indeed, a lack of alignment in this area is likely fueling the current wave of virulence. The meeting between Kim and Trump is scheduled for June 12th. Although history is ripe with examples of how mismatched expectations and underlying mistrust can quickly derail diplomacy, the current easing of tensions on the Peninsula should be met with cautious optimism. It is a welcome change to a situation that was seemingly on a nuclear collision course. Japan Since the end of World War II, Japan’s constitution has retained a unique feature known as the pacifist clause, or Article 9. The clause rejects the use of force to settle international disputes and prohibits a standing military, although Japan does maintain a Self Defense Force. This defense posture is enabled by the U.S. – Japan Treaty of Mutual Cooperation and Security which permits the U.S. to base forces in Japan in exchange for promises to defend Japan in the event of an attack. However, the strengthen of this alliance and future viability of Japan’s pacifist character has been tested by the growing North Korean nuclear threat and skepticism about U.S. commitment to extended deterrence. For example, after two of North Korea’s missile tests in 2017 flew over Japan, Prime Minister Shinzo Abe declared it was time to amend Japan’s constitution to allow a permanent military with expanded mandate. Critically, Japan has significant latent nuclear weapons capabilities due to it civilian nuclear power industry. While a signatory to the NPT, most analysts believe that should Japan decide to sprint for the bomb, it could do so in a relatively short timeframe.11 That said, nuclear acquisition in Japan remains highly unpopular. A recent survey found that even if North Korea does not give up its weapons, 69% of Japanese oppose developing a deterrent of their own.12 Nonetheless the credibility of the U.S. security guarantee plays an important non-proliferation role, especially dissuading the political leadership of the utility of acquiring nuclear weapons. To that end, the 2018 NPR sought not only to deter North Korean aggression against Japan, but also to assure Japan such actions are unnecessary. The response from the Japanese government indicted strong support for the Trump administration’s NPR: Japan highly appreciates the latest NPR which clearly articulates the U.S. resolve to ensure the effectiveness of its deterrence and its commitment to providing extended deterrence to its allies including Japan, in light of the international security environment which has been rapidly worsened since the release of the previous 2010 NPR.13 This statement signals a continued willingness to stand with the United States in confronting the North Korean threat, indicating the assurance goals of the 2018 NPR have been achieved. Indeed, despite media reports that Japanese leadership has been frustrated by its exclusion from the summit process, no major schisms have been reported between the U.S. and Japan regarding the U.S. approach to mitigating the North Korean threat. It is worth noting, however, that the Japanese public is highly skeptical the North Korean nuclear issue can be resolved. According to the same survey study, 67% of respondents believe the situation “won’t be resolved.”14 Moreover, the reception of the NPR was not uniform across the political spectrum; some opposition party leaders condemned the document calling it an effort to “[turn] back the clock.”15 The North Korean nuclear program presents an acute threat to South Korea and Japan. From the South Korean and Japanese perspectives, fear that North Korea might use its nuclear weapons in a conflict has generally been compounded by a lack of certainty regarding the strength of U.S. extended deterrence in the region. The 2018 NPR sought to assuage those fears by communicating U.S. resolve to defend its allies and by investing in a more flexible nuclear deterrent. The document was welcomed by South Korea and Japan and is likely achieving its goal of assurance. While the bite of international sanctions likely played the largest role in bringing North Korea to the negotiating table, the 2018 NPR also contributed to the current détente by demonstrating the commitment of the U.S. extended deterrence to allies in the region. Footnotes2018 Nuclear Posture Review. Department of Defense. Retrieved from: https://media.defense.gov/2018/Feb/02/2001872886/-1/-1/1/2018-NUCLEAR-POSTURE-REVIEW-FINAL-REPORT.PDF. Trump ‘seeking nuclear war’ with new posture: North Korean institute. The Japan Times. February 7, 2018. Retrieved from: https://www.japantimes.co.jp/news/2018/02/07/asia-pacific/politics-diplomacy-asia-pacific/trump-seeking-nuclear-war-new-posture-north-korean-institute/#.WuevNNMvwyk. Sang-Hun, Choe. Two Koreas, Split by War, Use Olympics to Make Rare Shows of Unity. The New York Times. February 8, 2018. Retrieved from: https://www.nytimes.com/2018/02/08/world/asia/olympics-north-korea-joint-team.html. And, Sang-Hun, Choe and Rich, Motoko. Can South Korea’s Leader Turn an Olympic Truce Into Lasting Peace? The New York Times. February 25, 2018. Retrieved from: https://www.nytimes.com/2018/02/25/world/asia/north-korea-olympics-peace.html?action=click&contentCollection=world&module=NextInCollection®ion=Footer&pgtype=article&version=series&rref=collection%2Fseries%2Folympics-international-2018. McInnis, Kathleen J. The North Korean Nuclear Challenge: Military Options and Issues for Congress. Congressional Research Service. November 6, 2017. Retrieved from: https://fas.org/sgp/crs/nuke/R44994.pdfU.S. TNWs were removed in 1991 in an effort convince North Korea to abandon its nuclear ambitions.Ye Hee Lee, Michelle. More than ever, South Koreans want their own nuclear weapons. The Washington Post. September 13, 2017. Retrieved from: https://www.washingtonpost.com/news/worldviews/wp/2017/09/13/most-south-koreans-dont-think-the-north-will-start-a-war-but-they-still-want-their-own-nuclear-weapons/?utm_term=.db6f0f484bfd. It should be noted the only TNW option for redeployment in the current stockpile is the B-61 gravity bomb which would require DCA for delivery. To that end, some have called for deploying DCA to South Korea and Japan to counter North Korean aggression. See: Payne, Keith B. and Foster, John S. A New Nuclear Review for a New Age. National Institute for Public Policy. April 2017. P 12. Retrieved from: http://www.nipp.org/wp-content/uploads/2017/06/A-New-Nuclear-Review-final.pdf. 2018 Nuclear Posture Review. U.S. nuclear review reaffirms commitment to extended deterrence for allies: Seoul official. Yonhap News Agency. April 4, 2018. Retrieved from: http://english.yonhapnews.co.kr/search1/2603000000.html?cid=AEN20180204004900315. Sang-Hun, Choe. Kim Says He’d End North Korea Nuclear Pursuit for U.S. Truce. The New York Times. April 29, 2017. Retrieved from: https://www.nytimes.com/2018/04/29/world/asia/north-korea-trump-nuclear.html. Lewis, Jeffery. The Word That Could Help the World Avoid Nuclear War. The New York Times. April 4, 2018. Retrieved from: https://www.nytimes.com/2018/04/04/opinion/avoid-nuclear-war-denuclearization.html. Pilat, Joseph F. Report of Workshop on Nuclear Latency. Woodrow Wilson International Center for Scholars. October 2, 2014. Retrieved from: https://www.wilsoncenter.org/sites/default/files/Report–Workshop%20on%20Nuclear%20Latency–20141002.pdf. And, Mehta, Rupal N., Is a Nuclear-Armed Japan Inevitable? War on the Rocks. June 9, 2016. Retrieved from: https://warontherocks.com/2016/06/is-a-nuclear-armed-japan-inconceivable/. Telhami, Shibley. Americans and Japanese are pessimistic about ending North Korea’s nuclear program and oppose military options. Where does that leave them? The Brookings Institute. January 22, 2018. Retrieved from: https://www.brookings.edu/blog/order-from-chaos/2018/01/22/americans-and-japanese-are-pessimistic-about-ending-north-koreas-nuclear-program-and-oppose-military-options-where-does-that-leave-them/. The Release of the U.S. Nuclear Posture Review (NPR). Statement by Foreign Minister Taro Kono. The Ministry of Foreign Affairs of Japan. April 3, 2018. Retrieved from: http://www.mofa.go.jp/press/release/press4e_001893.html. Telhami, Shibley.Japan’s dependence on nuclear umbrella highlighted as it hails new US policy. The Mainichi. February 5, 2018. Retrieved from: https://mainichi.jp/english/articles/20180205/p2a/00m/0na/012000c.