The most practical way for Japan and South Korea to ensure their security independently of the United States is to strengthen their relationship, eventually evolving into a formal alliance. An unspoken motivation behind Japanese Prime Minister Ishiba Shigeru’s push for an “Asian NATO” may indeed be the development of a security relationship with South Korea. For both countries, achieving true security independence is the only way to alleviate the security dilemma posed by their military dependence on the United States, particularly given growing concerns about rising security. American isolationism.
Ishiba’s extensive experience in national defense shapes his realistic view of the world. Therefore, its main motivation for pursuing security independence is to safeguard Japan’s geopolitical interests in the face of growing threats from China, North Korea, and Russia. This strategy is timely, given growing uncertainties about America’s commitment to Japan’s defense. And Ishiba’s proposal to station the Japan Self-Defense Forces (SDF) on Guam could be a feasible step toward improving Japan’s military maneuverability.
Despite his ambition, Ishiba understands that a completely militarily independent Japan through an “Asian NATO” cannot be built overnight. Nevertheless, its conception of collective security in Asia reflects a long-term strategy, with South Korea becoming Japan’s most viable regional ally. The signal was warmly received by South Korea. In his first phone call with Ishiba, South Korean President Yoon Suk Yeol expressed support for stronger security ties with Japan, emphasizing shared values and geopolitical interests: the two democratic nations face threats from North Korea, whose progress in nuclear capabilities is a growing concern. Adding to this threat is North Korea’s recent transfer of military technology from Russia and closer cooperation with China, which have exacerbated regional tensions.
Although Tokyo and Seoul currently depend on Washington for their defense, their geographic proximity makes them each other’s most immediate partners in the event of a regional security crisis. South Korea’s three-axis system, which includes missile defense and counterattack capabilities, is geopolitically more crucial to Japan’s defense against regional threats than the uncertain level of U.S. aid. Strengthening bilateral defense cooperation between Seoul and Tokyo therefore constitutes a strategically logical step for both countries.
However, Japan’s desire to strengthen its security ties with South Korea does not necessarily mean excluding the United States. The underlying motivation for both countries to seek greater security independence from their primary security guarantor stems from the security dilemma created by massive US involvement in the Asia-Pacific region. For South Korea, the asymmetrical nature of its alliance with the United States has limited its influence. Washington has historically restricted South Korea’s access to advanced military technology, while pressuring Seoul to pay more for the alliance. This has increased South Korea’s military burden and complicated its relations with North Korea, prompting Seoul to cautiously seek greater security autonomy.
Japan faces a similarly complex dilemma. Although South Korea must always prepare for potential conflict with North Korea, Japan has a choice. If war broke out across the Taiwan Strait, the United States would need Japan’s permission to use its military bases to deploy forces to defend Taiwan. This puts Japan in a difficult position: a deal risks provoking Chinese retaliation, while refusal could undermine the U.S.-Japan alliance, Japan’s main security guarantee.
For Japan, the fundamental goal of military buildup is to strengthen deterrence and self-defense, not to provoke conflict. Although close ties with the United States provide security guarantees, they can also limit Japan’s autonomy in making critical security decisions. Japan therefore has every reason to pursue its security independence, as does South Korea. Yet, given the limited military capabilities of both countries, it is not practical to achieve full security independence individually. The most feasible way forward is through closer cooperation with each other.
However, a closer alliance between Japan and South Korea could push them to prioritize East Asian interests, which would essentially reset U.S. power projection in the Asia-Pacific region. It is therefore not surprising that Washington does not fully share Ishiba’s enthusiasm for an “Asian NATO.” US Deputy Secretary of State Daniel Kritenbrink expressed skepticism, saying it was “too early to talk about collective security in this context” and emphasizing that the US was focused on “investing in formal architecture existing in the region” and strengthening informal relationships. But does the current U.S.-led regional framework actually improve the security of Japan and South Korea?
The answer is no. While U.S. security treaties with Japan and the Republic of Korea formalize their alliances with America, their ties to other U.S. allies in Asia – such as the Philippines and Indonesia – remain , at best, quasi-alliances. In practice, the United States exerts significant influence over these countries’ decisions to provide military assistance in the event that Japan or South Korea faces a security threat. As a result, Tokyo and Seoul must constantly prove themselves to be credible allies of Washington to secure future support.
A recent example is Japan and South Korea’s substantial economic and military aid to Ukraine, aimed at strengthening ties with the US-led NATO. However, the move risks stoking fears of encirclement in China and North Korea, thereby escalating regional tensions. Additionally, it strains the military resources of both countries, potentially undermining their own defense build-up. By aligning too closely with U.S. and European interests, Tokyo and Seoul risk losing the flexibility needed to manage their own economic and security priorities.
As the United States remains enmeshed in regional conflicts such as those in Ukraine and Gaza, its influence in Asia inevitably diminishes, providing an opportunity for middle powers like Japan and South Korea to reevaluate their defense strategies. in an increasingly complex geopolitical landscape. Although unresolved historical disputes may temporarily hinder closer security cooperation between the two countries, growing security threats in the region dictate that a stronger relationship between Japan and South Korea is the most viable to ensure the security of both countries while gradually obtaining greater autonomy from America.
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