The long-awaited return of a joint Search and Rescue Exercise (SAREX) between the Republic of Korea (ROK) Navy and the Japanese Maritime Self-Defense Force in the East China Sea was confirmed earlier this month.
After nine years, the exercise on June 7 represented an important change in the security framework in the region and a sign of improved relations between two of its leading powers.
Since taking office in June 2025, South Korean President Lee Jae Myung has been re-evaluating the country’s foreign policy and approach to defense cooperation. He has advocated for a pragmatic approach to foreign policy, with decision-making informed by a rigorous assessment of the strategic environment. That assessment reflects the reality of a security environment that continues to deteriorate.
The persistent threat posed by North Korea continues to shape South Korea’s strategic calculations, particularly as Pyongyang advances its nuclear capabilities. North Korea has already conducted six nuclear tests and is developing a diverse range of weapons of mass destruction, from intercontinental ballistic missiles capable of reaching the entire U.S. mainland to short-range ballistic missiles capable of flying at low altitude on irregular trajectories.
On June 8, just a day after the ROK-Japan search and rescue exercise, Chinese President Xi Jinping traveled to Pyongyang for a two-day summit with North Korean leader Kim Jong-un in a sign of growing ties between the two countries.
Coverage of the summit in North Korean and Chinese media notably failed to mention calls for the country’s denuclearization. This has largely been read as a diplomatic win for Pyongyang, and a step backwards from the meeting between Xi and U.S. President Donald Trump and President in May this year where the leaders reiterated a commitment to the denuclearization of North Korea.
Pyongyang’s growing military ties with Russia also pose challenges for Seoul's regional security, elevating the risk that North Korea may acquire sophisticated military technology, which it could deploy against either South Korea or the U.S.
Under Lee, South Korea has also been undertaking a strategic reset towards its relationship with China, engaging in back-to-back meetings with Xi in November 2025 and January 2026. Lee has executed a diplomatic balancing act, avoiding discussion of contentious issues including Taiwan and North Korea with China, whilst simultaneously seeking to strengthen its military and economic relationship with the United States.
For the last two decades, China has been South Korea’s largest trading partner. Now, Lee is seeking to address this vulnerability and reduce the country’s exposure to China. South Korea is particularly sensitive to concerns around China’s use of economic coercion, which have had considerable economic impact on South Korea in the past.
But this balancing act between two superpowers will inevitably have limitations. These constraints are becoming increasingly visible as South Korea manages an unpredictable United States which has suggested that it may reduce its overseas military presence and demand greater defense commitments from its allies.
Now, despite historical tensions with Japan, the geopolitical environment is forcing a reassessment of regional security partnerships.
The return of the SAREX is the latest sign of a willingness to draw a line under previous disputes and secure South Korea’s national interests in the Indo-Pacific by forging a closer relationship with Japan, a like-minded, democratic, U.S. ally in the region.
Japan, as South Korea’s neighbor, faces similar threats. North Korea is perceived as an immediate and critical threat to Japan, particularly in light of its continued missile and nuclear development. Japan is also pushing for international support to prevent abductions of Japanese citizens by North Korea which has caused relations between the two nations to deteriorate.
Japan-China relations have also been fraught in recent months, after repeated incursions into Japanese territory by Chinese vessels and aircraft. Most recently, Chinese vessels passed through Japanese waters surrounding the Okinawa islands, in what could have been a dangerous escalation.
Lee and Japanese Prime Minister Sanae Takaichi have both recognized these shared ambitions and threats, and have been fostering a mutual trust through shuttle diplomacy in recent months. The two leaders have quietly moved past historical grievances, through a series of high-level diplomatic meetings, with three bilateral summits in the past year.
Most recently, Takaichi traveled to Andong in South Korea, Lee's hometown, in May. This followed Lee’s visit to Takaichi's hometown of Nara in January. This rare exchange symbolizes the close and positive relationship between the two leaders, helping to stabilize bilateral ties and pave the way for deeper cooperation in the fields of security and defense.
While historically much of the cooperation has been conducted trilaterally, alongside the U.S., the two leaders have reinstated annual visits of defense ministers, restarted the joint search and rescue exercises and installed new avenues for bilateral dialogue and cooperation.
In late June, Japanese Defense Minister Shinjiro Koizumi and South Korean Defense Minister Ahn Gyu-back held high-level talks. While this may appear to be just another ministerial meeting, it is in fact an important test of South Korea’s strategic direction. At a time of heightened geopolitical risk and regional instability, South Korea’s foreign policy is gradually shifting away from traditional hedging towards deeper cooperation with like-minded partners such as Japan.
Japan and South Korea not only share common values but also common security interests. Like South Korea, Japan faces the persistent threat posed by North Korea, as well as the growing challenges presented by China and Russia as they deepen their ties with Pyongyang. By maintaining the minimum level of defense capability necessary for self-defense and strengthening deterrence against North Korea and other regional actors of concern, Japan also contributes to South Korea’s security.
Japan also plays a significant role in enforcing international sanctions against North Korea. As part of its routine surveillance activities, Japan monitors suspected ship-to-ship transfers that may violate U.N. Security Council resolutions. In addition, U.S. bases in Japan enable Australia, Canada and several European countries to deploy assets for sanctions monitoring operations, further underscoring Japan’s important contribution to regional security.
As regional tensions rise in the Indo-Pacific, the question is no longer whether South Korea can afford to put historic disputes behind it, but whether the country can afford not to.
Retired Lt. Gen. Chun In-bum is the former commander of the Republic of Korea Army Special Warfare Command.