Seoul-Tokyo cooperation essential in Indo-Pacific

Chun In-bum

As conflict in the Middle East draws more of Washington’s resources and attention, the United States has partially removed defensive military assets from South Korea, including the terminal high-altitude area defense (THAAD) missile defense system that constitutes a major part of Seoul’s deterrence posture.

While the U.S. and South Korea are treaty allies with a cast-iron commitment, President Lee Jae Myung must bolster partnerships with other likeminded nations that treat open sea lanes and international law as sacred.

Lee has been active in this area, strengthening relationships with various nations. In just the last four months, he has met with Prime Minister Sanae Takaichi of Japan and President Emmanuel Macron of France.

However, under the banner of “pragmatic diplomacy” foreign policy, Lee also met with Chinese President Xi Jinping in January, seeking a “new phase” of ties.

In the current geopolitical climate where international law is being increasingly ignored, South Korea must not forget its core security interests. This means pursuing closer ties with the U.S. and Japan, both of whom value and are capable of safeguarding our freedoms and democratic way of life.

There are, of course, compelling reasons to reset Korea’s relations with China, and Lee will point to 64 billion won (43.4 million dollars) in new export deals and memoranda of understanding as evidence that pragmatic diplomacy can have tangible benefits for our economy.

But we must remain clear-eyed about the security threat China poses to the region. First, South Korea is severely exposed if there is an escalation of tensions in the Taiwan Strait, a region that holds many of the strategically vital submarine cables the country depends on for its internet connections.

China’s large-scale military exercises around Taiwan at the end of last year were a clear demonstration of Beijing’s capabilities, a reminder that it can seize Taiwan by force.

Second, China is also increasingly aligned with Russia, a nation that is waging a full-scale war against a sovereign nation and has a track record of undermining democracy around the globe.

Third, Beijing remains the primary sponsor of North Korea, a historic relationship that dates back to the division of our peninsula.

The U.S. will always remain a close ally and vital security partner to South Korea. But in these unstable times, South Korea must also look to regional powers for its defensive partnerships.

Japan is a key geopolitical actor in East Asia and is investing in its Self-Defense Forces to respond to what it describes as the “most severe and complex” security environment since the end of World War II. Japan’s defense budget will exceed 84 trillion won for the first time in 2026, allocating substantial funding to long-range missiles and unmanned capabilities.

Additionally, Japan’s defense minister Shinjiro Koizumi has expressed his intention to bring forward the revision of important security documents and to ease many of Japan’s strict arms export restrictions.

Since December 2023, South Korea, Japan and the U.S. have collaborated on real-time North Korean missile warning data sharing , enabling the monitoring and assessment of projectiles.

In a world of increasingly sophisticated military threats where South Korea’s ability to respond rapidly in coordination with allies is paramount, the benefits of closer alignment with Japan to deter a primary security threat are clear.

Most importantly, Japan’s vision for East Asia closely aligns with South Korean values, including democracy and the rule of law.

Japan’s “Free and Open Indo-Pacific” vision is premised on upholding the rule of law, free trade and the peaceful resolution of disputes. Rather than trying to define its position through one-on-one relations with major powers, South Korea should, like Japan, act as a defender of the international order within a broader vision that values inclusivity and seeks prosperity across the region and the world.

Pragmatic diplomacy is a well-intentioned idea, and it is right for South Korea to strive for closer relations with all its neighbours. But we live in turbulent times. South Korea must prioritise its core national security interests. That means closer relations with Japan.

In January, Takaichi invited Lee and Koizumi invited his South Korean counterpart Ahn Gyu-back to their respective hometowns for talks. The hospitality made it clear that South Korea-Japan relations are better than ever.

It is now crucial that Tokyo and Seoul build on this momentum to strengthen their partnership and address the growing threats posed by China and North Korea. However, this must be done with Washington.

Fortunately, the fragile ceasefire in the Iran war provides an excellent opportunity to re-engage Washington. Now that the U.S. has the capacity, Tokyo and Seoul must direct Washington’s attention to the threats in the Indo-Pacific and the necessity of the U.S.-Japan-South Korea alliance in countering them.

Retired Lt. Gen. Chun In-bum is the former commander of the Republic of Korea Army Special Warfare Command.