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Secretary James Mattis's Visit to South Korea and Japan

Background on the Issues

Secretary of Defense James Mattis traveled to the Republic of Korea (ROK) and Japan to meet with senior officials in both countries, including South Korean minister of national defense Han Min-koo and Japanese minister of defense Tomomi Inada. He reassured both allies of the United States’ ongoing nuclear defense guarantee and security commitment, while also keeping U.S.-Japan-ROK security cooperation moving forward.

Secretary Mattis’s visit took place as South Korea grapples with a leadership crisis that could result in the election of a new president by the summer. Potential presidential candidates have voiced concerns with basing a Terminal High Altitude Area Defense (THAAD) antimissile system in South Korea, South Korea’s growing partnership with Japan under the Park administration, and the ROK’s focus on the United States as its major security provider and have indicated a desire to strengthen relations with China and re-engage North Korea.

Japan, for its part, hopes to preserve the status quo that emerged under the Obama administration. Critical issues for Tokyo are maintaining and strengthening the U.S.-Japan alliance as a foundation for East Asian security and working to build on positive developments in trilateral cooperation with the United States and the ROK.

The following NBR publications provide expert analysis of these and other issues related to the visit.


The January 2017 issue of Asia Policy includes roundtable essays by Sheila A. Smith and Sue Mi Terry that assess the key issues in the U.S. alliances with Japan and South Korea and consider policy options for the Trump administration.

In an NBR Special Report on U.S.-ROK-Japan Trilateralism, Daniel Sneider, Yul Sohn, and Yoshihide Soeya, respectively, discuss the importance of trilateralism among the three countries and offer insights into how to improve the relationship.


As China increases its activities around the disputed Senkaku Islands, the territorial disputes between China and Japan in the East China Sea will remain a critical issue for the U.S.-Japan alliance. The Maritime Awareness Project features a range of resources for better understanding the maritime claims in the region, including an interactive map, country profiles, commentary, and backgrounders.

The Asia Policy roundtable “Non-claimant Perspectives on the South China Sea Disputes” includes essays on Japan and South Korea in which regional experts examine these countries’ interests and concerns.


Matthew Kroenig’s NBR Special Report Approaching Critical Mass: Asia’s Multipolar Nuclear Future analyzes the dynamics of the multipolar nuclear order in Asia, including the challenges of extended deterrence and assurance of allies such as the ROK and Japan.

The January 2017 issue of Asia Policy features a roundtable on the North Korean nuclear threat in which regional experts discuss the shared Chinese, Japanese, South Korean, and U.S. interests in a nuclear-free Korean Peninsula and consider strategies for these countries to better cooperate on achieving this goal. An article by Robert Huish in the same issue examines the ineffectiveness of current sanctions on marine traffic into North Korea.


Victor Cha and Ellen Kim’s Asia Policy article "Between a Rock and a Hard Place: South Korea’s Strategic Dilemmas with China and the United States” describes the impact of the growing Sino-U.S. rivalry on the China-ROK relationship and argues that South Korea’s relations with the United States and China “need not be a zero-sum game.”


Strategic Asia 2016–17 contains chapters on the strategic cultures of Japan, South Korea, and the United States. Alexis Dudden examines divisions in Japan’s strategic culture and assesses the implications for U.S. security interests. David C. Kang and Jiun Bang argue that South Korea’s strategic culture based on autonomy only partially corresponds to its relative power, economic wealth, and political system. Colin Dueck analyzes the tension in U.S. strategic culture between the promotion of a liberal international order and the emphasis on limited liability and assesses the implications for U.S. foreign policy.


The 2015–16 volume of Strategic Asia includes chapters on the foundations of national power in Japan and South Korea. Michael Auslin argues that Japan, despite its limited natural resources, possesses “the economic strength, political cohesiveness, and state infrastructure to develop and deploy comparatively significant military capabilities in Asia.” Chung Min Lee assesses South Korea’s economic and military strengths and weaknesses and analyzes the challenges that the country will face over the next decade.

Secretary of Defense James Mattis greets U.S. Marine Corps Gen. Joseph Dunford, Chairman of the Joint Chiefs of Staff, after arriving at the Pentagon in Washington, D.C., Jan. 21, 2017. (DOD photo by Air Force Tech. Sgt. Brigitte N. Brantley. Some rights reserved.)

Strategic Asia 2016–17: Understanding Strategic Cultures in the Asia-Pacific, the sixteenth volume in the Strategic Asia series, examines how the region's major powers view international politics and the use of military force. Learn more.