South Korea and Japan Cement Bilateral Security Ties

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Almost unnoticed in the Western press, on June 1, 2024, South Korean defense minister Shin Won-sik and Japanese defense minister Kihara Minoru reached an agreement on the margins of the Shangri-La Dialogue in Singapore to normalize bilateral defense ties, which have been essentially on ice since 2018. Despite the usual focus on U.S.-China relations at the Shangri-La Dialogue, and the meeting between U.S. secretary of defense Lloyd Austin and his Chinese counterpart, this announcement was easily the most significant outcome from the event.

In December 2018, tensions flared up between Japan and South Korea after an incident between the Japan Maritime Self-Defense Force (MSDF) and the Republic of Korea Navy (ROKN). Japan claimed that a South Korean naval destroyer had directed its fire-control radar at an MSDF patrol aircraft conducting a surveillance operation near the Korean Peninsula in the East Sea/Sea of Japan. The ROK Ministry of Defense denied Japan’s allegation, saying that it was not operating the fire-control radar but rather was tracking a distressed North Korean fishing boat at that time. Instead, the South Korean side accused the Japanese aircraft of making a dangerous low flyover of its navy vessel.

Despite the overall progress in Japan-ROK ties since last year, and the remarkable trilateral summit at Camp David last August, this issue has remained unresolved, and bilateral defense ties have remained frozen—until the meeting in Singapore. The subject of intense, quiet negotiations for months, the agreement is a breakthrough that further reinforces the new era in bilateral ties and the prospect that the improvement may prove to be lasting. In it, the two governments agreed to resume defense exchanges, including a regular dialogue at the vice minister level and high-level engagements between the SDF and the ROK military.

The deal between Seoul and Tokyo is significant for several reasons. First, it signals the growing strategic convergence between Tokyo and Seoul, in ways that go far beyond a common response to the North Korean threat—which has long been the primary basis for security cooperation between the two countries. The joint statement issued after the meeting includes this remarkable line: “The ministers shared the view that bilateral security cooperation between the ROK and Japan benefits the shared values and common strategic interests of the two countries, and is the foundation of Japan-ROK-U.S. security cooperation. It not only serves to deter the threat from North Korea but is indispensable to realizing a free and open Indo-Pacific” (authors’ translation). This language is the closest the two governments have come to a joint security declaration—a significant statement of common values and common purpose.

Second, the agreement affirms that the deepening networks of security cooperation across the region are organic—and not simply an artifact of U.S. policy. At a time when political uncertainty in the United States clouds the future of U.S. engagement in the region, Japan and South Korea have sent a powerful message that like-minded partners are coming together to uphold a rules-based liberal order—a “new convergence” around shared principles, as Secretary of Defense Austin put it in his speech at the Shangri-La Dialogue on June.

Third, the deal established a framework that will create rules of engagement and reduce the risk of future mishaps between the two militaries, which often operate in close proximity to one another. Specifically, the two defense ministers agreed to improve radio communication procedures between naval vessels and aircraft to avert any misunderstanding about their intent when two countries have an unplanned encounter at sea. In addition, both sides agreed to adhere to the Code for Unplanned Encounters at Sea, a set of guidelines established by key countries in the region in 2014.

Fourth, the agreement came just six days after the China-Japan-ROK trilateral summit on May 26–27. The juxtaposition of these two events clearly shows that while the China-Japan-ROK trilateral summit called for lofty cooperation goals like a trilateral free trade agreement—which is unlikely anytime soon—cooperation among Japan, South Korea, and the United States is achieving concrete and practical outcomes at an accelerating pace.

Even as the defense ministers met in Singapore, bilateral and trilateral ties were advancing on other fronts. On May 31, Deputy Secretary of State Kurt Campbell hosted his Japanese and South Korean counterparts for an intimate retreat in rural Virginia, where they discussed a wide range of issues. Plans are afoot for another leaders’ meeting, perhaps on the margins of the NATO summit in Washington in July.

Finally, the defense agreement at Shangri-La and the trilateral meetings last week manifest a continued political commitment by both Japanese and South Korean leaders to stay the course despite domestic unpopularity at home. Neither Kishida nor Yoon win much praise for these policies, the latter having suffered a major midterm election defeat in April and the former on the ropes in the national polls. But the two leaders are pursuing policies in the national interest, which is the definition of leadership.

Events over the last year do not erase the long history of challenges in Japan–South Korea relations. Difficult issues remain, and different leaders in both countries could choose to reverse these gains in the pursuit of short-term political ends. But the strategic foundation for cooperation between the two countries has arguably never been broader or deeper, and each new agreement, each new step forward, raises the cost to future leaders of regression.

Christopher Johnstone is senior adviser and Japan Chair at the Center for Strategic and International Studies (CSIS) in Washington, D.C. Victor Cha is senior vice president for Asia and Korea Chair at CSIS.

Victor Cha
Senior Vice President for Asia and Korea Chair